Pier and Beam Foundations – KHouse Progress

Bob Borson —  June 12, 2014 — 105 Comments

On the residential part of our practice, we do a lot of pier and beam foundations. There are other options available to us -some include post-tensioned slab on grade and plain ol’ slab on grade, and all of these options are fine under the right circumstances but if I had my pick (which I normally do) we recommend the pier and beam structural foundation. The soil in my area of practice tends to be expansive because it contains a healthy dose of clay, which expands and contracts as moisture enters the equation. Add water, through rain and irrigation, and the soil expands. Remove water due to hot and dry conditions, and the soil contracts. All this soil movement adds up to cracks in the house. Because we like to help eliminate the movement issues that come along with expansive soil, we like designing with a pier and beam foundation.

Most people have heard of a pier and beam foundation at some point in their lives but more times than not, they don’t really understand how it works – even the “experts” get it wrong. I had a home inspector tell me, as he was inspecting a house I was in the process of buying, that the house had structural issues because there wasn’t dirt under the grade beam where he had checked.

Home Inspector: This house has structural issues.
Bob: Really? What did you find?
Home Inspector: I noticed when I was in the crawl space that there were gaps under the grade beam where the dirt was missing.
Bob: Right … and exactly what was the problem?
Home Inspector: Your beam will eventually sag if it isn’t supported properly. You’ll need to get someone down in the crawl space and put some dirt in.
Bob: What?!? There isn’t supposed to be dirt under the grade beam … you do know that dirt doesn’t hold the beam up, that’s the job of the piers.
Home Inspector: Son, I’ve been doing this a long time.
Bob: Uh-huh … right.

For the record, if it wasn’t already clear, dirt DOES NOT support the grade beam in a pier and beam foundation.

Since a number of people don’t seem to understand this concept, I thought I would whip together some sketches to help illustrate my point. If you can’t read drawings, hopefully my explanation will be good enough for you to understand.

Pier and Beam composite 01

Here is a typical wall section through a pier and beam foundation. The grey part is the house and for our purposes, it doesn’t matter in this conversation. The important thing to note is that a pier (think of it as a concrete column) is drilled down through the dirt until it can bear on rock. That’s important because rock doesn’t expand or contract based on the water content of the surrounding areas.

The grade beam is a concrete beam that spans from pier to pier – just like a beam that’s probably in the ceiling above your head spanning from wall to wall.

Underneath the grade beam are “void cartons” or “void forms” (it would have helped if I had labeled them in the sketch above, as it is, it is shown as a gray rectangle with two diagonal lines in it.) Believe it or not, void forms are made out of cardboard, and the concrete gets poured on top of them. They are strong enough to support the weight of wet concrete but over time, long after the concrete has cured and become hard, the cardboard will rot away and leave a void.

The last thing to note in the sketch above are the “soil retainer boards”. These are basically plastic boards that keep the surrounding dirt out of the space the void carton creates when it rots away.

Pier and Beam composite 02

This is a look at a typical grade beam when the void form has rotted away. There is now an airspace between the bottom of the grade beam and the dirt below. This is a good thing … it’s an important thing, you want this gap.

Pier and Beam composite 03

Why would you want a gap? You want it so that when the surrounding dirt absorbs water and expands, the dirt doesn’t push up against the underside of the grade beam. Having this gap is what allows you to not worry about cracks in your brickwork, or having doors stick seasonally. Piers, bear on bedrock, grade beams sit on piers, and no dirt under your grade beam means your house doesn’t move.


I told you all that so that maybe these pictures would make a little more sense. We poured the grade beams at the KHouse recently and it was quite the show for a residential project. 13 concrete trucks, spaced 30 minutes apart, helped get this foundation pour done and we are now about 80% complete. All that’s left are the basement walls, driveways, sidewalks, and exterior stairs.

KHouse Modern pump truck 01

In order to reach all points on the site without damaging the trees, the contractor had to use a concrete pump truck with a giant arm on it. This machine takes the concrete in at the rear and pushes it through a bunch of pipes connected to the arm.

KHouse Modern loading concrete into pump truck

All the concrete goes into the hopper here … easy.

KHouse Modern pump truck large tree

This was one of the trees we had to avoid messing with – it was a main consideration in deciding how the concrete would be placed. I don’t get to use these pump trucks too often on residential jobs, but they are extremely common on commercial jobs.

KHouse Modern looking over ite prior to concrete pour

This is the pump arm expanding out – you can start to get a good feel for just how far it can reach. Pouring concrete is incredibly difficult and back-breaking work, I frequently think that other than being a roofer in the summer, this is the worst job on a construction site … except for the guy who controls the pump arm – that’s the sweetest gig ever on a construction site.

KHouse Modern pump truck remote operator controls

Here is a look at the controller for the pump arm. It’s really like playing video games all day – at least that’s what the guy told me, and he ought to know. He stands in the shade fiddling with the joy sticks while everyone else is breaking their back pushing wet concrete around.

KHouse Modern loading concrete into pump truck

KHouse Modern concrete pump boom fully extended

KHouse Modern pouring concrete

These were some of the guys locating the concrete into the plywood forms. As I took this picture, the guy in the front wearing the plaid shirt said “you really don’t want to stand there”. I know, but I wanted to take the picture …. and about 5 seconds later, an air bubble came through the line, the concrete coming out kind of spluttered a little bit and then *BOOM* I was splattered head to toe in concrete (I didn’t take a picture of that). The only saving grace, as all the concrete guys were laughing, was that the contractor was standing right next to me and got covered as well.

KHouse Modern contractor monitoring the concrete pour

Speaking of the contractor – that’s him in the white polo shirt sitting atop the concrete mixing truck. That’s called “doing your job.”

KHouse Modern overlooking part of the site

This is looking across the top of the grade beams – the dark gray stripe in the middle is the wet concrete. From the top of the grade beam, you can get a sense of how deep the crawl space will be – just under 4′ total. In this project, we are installing our air-handling units below the floor and this is where they will go.

KHouse Modern vibrating concrete

Just because no post where pouring concrete is discussed would be complete without talking about a vibrator, I feel it is incumbent on me to point it out. As the concrete is poured into the formwork, the vibrator is inserted into the concrete to make sure that the aggregate is uniformly distributed and that there aren’t any air pockets. Pretty simple job but there is some skill required … too little vibration and you don’t get the concrete distributed correctly, too much and you can over mix the concrete and settle the aggregate towards the bottom rather than uniformly.

KHouse Modern testing the concrete temperature

The last thing I wanted to point out is the concrete testing. This doesn’t happen on many residential projects but this isn’t just any residential project. An independent testing company came out and check the concrete from two concrete trucks (selected at random) to perform slump tests and to take compression core samples. They measure the temperature of the concrete to make sure that the concrete hasn’t been sitting in the truck too long since it came from the batching plant and is still suitable for use.

KHouse Modern concrete slump test

Here is a collection of images showing a slump test being performed. They way it works is that the metal cone is filled in three loads, each load being tamped down 20 times with the metal rod. Then the cone is slowly lifted off and the cone placed next to the pile of concrete that it just uncovered. The metal rod is placed across the top and a measurement is taken from the rod down to the top of the “slumping” concrete. The amount of slump that takes place is an indicator of the strength of this load of concrete. I believe the structural engineer called for 3,500 psi concrete so we were looking for a 4″ slump – which is what we got. Too much slump and the concrete would have been rejected.

KHouse Modern finished grade beams

Just a few days later, all the plywood formwork gets removed and you can see the finished concrete product. Considering I know just how much work went into getting to this point, I am always amazed at how simple every looks … but looks can be deceiving. Getting something wrong here means everything after will be wrong. All the embed plates, drop heights, brick ledges, inverted brick ledges, joist pockets, etc. have to be coordinated and resolved. It looks simple because that’s the point.

KHouse Modern soil retainer boards detail

Here is a detailed look at what soil retainer boards look like … corrugated plastic. Surprised?

KHouse Modern soil retainer boards in place

In this picture you can see the three things that we’ve talked about in today’s post; the concrete grade beam, the soil retainer boards (the black panels above) and the cardboard void form (look to the left of the guy above – you can still see the void forms before they get covered up by the soil retainer boards).

KHouse Modern soil retainer boards

And here is a close up finished look at a corner – see that notch cut out of the soil retainer boards? That part of concrete is just a tiny bit of the pier that the grade beams sit on (if you want to see more about the piers on this project, read this).

KHouse Modern finished grade beams

Finally, this is the detached garage on the right and the main house on the left with a walkway in between. Soil retainer boards have been put in place on the house and you can see the pier at the bottom left-hand corner of the house. In the trenches, that you see to either sir of the walkway space, will be perimeter drainage pipes … but that’s a different post for a different day.

I’ve tried to walk the line between keeping things simple, but include enough information as to be of some benefit. On the day the concrete was poured at the KHouse, we brought a bunch of the staff out to see how things worked. We even met the owner on site and walked the concrete pour with him and explained what was happening. This sort of thing can seem really dry and boring but as I’ve mentioned on many occasions, you have to understand something in order to appreciate it. This is not an inexpensive foundation or project so all indications would tell me that the time we spend explaining what is going on at the site with the owner, the more excited he is becoming to what he will eventually receive.

I have no doubt that the stories our client will tell folks about his house will include more than just “this is white oak flooring” or “this is a pier and beam foundation.” He’ll be able to talk about the cut of the flooring and tell people “this is white oak flooring and this pattern is called “cathedraling” and that it took 13 loads of concrete to pour his grade beams … and I think that’s pretty cool.


Bob AIA signature

Print Friendly

even better

  • Jeff Fennell

    Bob, great site! I’m building a two story house in Houston Texas. The home is 3000 sq feet with 1500 sq ft on both floors. Can you tell me the approximate price difference of a slab foundation with post tension cables versus a pier and beam foundation? We love the pier and beam, but hear it is more expensive. Thanks.

  • tim

    need advise have a house on pier and beam that the ground is so moist that you can squeeze water out of it what will cause this problem i have proper vents by code what will cause all this moister to where it is growing mold on floor joist please help

  • Jeremy Newman

    Wow! Nice website and article. I live in central TX where the soil is very much black clay. I’ve got designs on a small guest house for dear mom. The plan is a 20 x 30 with a loft. We are doing most of the building ourselves. I am looking for a relatively inexpensive way to do a pier foundation. Can you point me in the right direction? I am a remodeling contractor and have lots of smart people to help but no one who has been solid on answers for a pier foundation house.

    • http://www.lifeofanarchitect.com Bob Borson

      if you are looking to do an inexpensive foundation, you shouldn’t start with the pier and beam. If you have a lot of expansive soil that you’re working with, you might even look at post-tensioned slab over fill. I would recommend that you talk to a structural engineer. We get a soils test done on all of our projects and the soils engineer ends up making design recommendations for different types of foundation systems based specifically on the finding from the site borings. typically these reports run around $1,200 but they are well worth the expense.

  • David Franklin

    Thanks for the great sketches and description of concrete pier and beam foundations. This is likely the best solution for the home I am currently planning. However, I do have a question. How do you support the garage slab. The garage slab must float on the expansive clay with adequate reinforcement and perimeter space to allow vertical movement or be poured on temporary cardboard/EPS forms, be highly reinforced and designed for bending and punching shear with sufficient distributed piers for the load. The perimeter must still be pier and beam to minimize vertical house movement and accommodate the garage door?

    • http://www.lifeofanarchitect.com Bob Borson

      without looking at the soils report, the generic answer is that the garage would be a structural slab on void cartons. The perimeter would still be pier and beam and the garage slab would simply “float” from edge to edge.

  • Jesse Strom

    I have a floor( that’s rotten) that is two foot off the ground, with so much moisture in the crawlspace it looks like its raining under the house. What kind of floor would be best to replace it with? And how do i do away with the moisture?

  • http://www.brotherscustomworks.com John Luther

    “There isn’t supposed to be dirt under the grade beam … you do know that dirt doesn’t hold the beam up, that’s the job of the piers.”

    Right, but you are speaking to your professional, layman and homeowner readers, and though it is obvious to some, what is shown in your sketches with the particular detail unmentioned in the text: one unknowing could be confused in thinking the carton forms (void boxes) run over the top of the piers – when carton forms are typically placed only in the beams, and the piers reach the bottom of the beams – being without separation (by carton form) of the pier and beam.

    Piers to sub-surface rock is nice, but sub-surface rock formations are rare in the Houston TX area. Our soil test – report most often reveal better bearing and more stables soils at 8′ – 12′ deep. The typical residential pier is 12″ shaft and 3′ “bell” (belled out aka reamed at bearing depth from 12″ shaft to 3′ integral pad. These called drilled and reamed piers (special tool for reaming).

    In this area, structural slabs, similar to a slab on grade, and post tension slabs are also built to include key load point piers.

    Unmentioned in your very informative article, a pier gains addition stability – durability, as the bearing depth is away from more drastic dry and wet conditions at and in shallower depths.

    Also interesting, an article for a beach hotel in Dubai reveals very deep shaft only piers (no reaming at depth) as the pier load calcs are based on the friction between the pier and sands that make up the composition below the hotel.

    • David Franklin

      Can you provide names of reliable foundation contractors with concrete pier and beam experience in the Houston area?

      • http://www.brotherscustomworks.com John Luther

        If you will send an email to jnbluther@yahoo.com, I can provide a foundation crew that I have used with great success and outstanding work since the mid 80s.

  • brandyromano

    My husband and I want to build in the next year or two near Tyler, TX every contractor I talk to about pier and beam looks at me like I’m crazy. My husband and I both prefer them especially for the purpose of future repairs as well as the way they feel. Why do so many contractors only use slabs when our soil here pretty much guarantees there will be cracks in them sooner rather than later. I would appreciate your insight on this.
    Thank you
    Brandy Romano

    • http://www.lifeofanarchitect.com Bob Borson

      Hi Brandy,
      The only thing I can think of that might be the reason some contractors are hesitant to build a pier and beam foundation is the cost. They are substantially more expensive than a slab on grade. At least, this is what I prefer to think rather than they don’t know how to build a pair and beam foundation and simply don’t want to mess with the process of building one.

      • tavana

        Hello Mr. Bob I am Muhammad, so I liked your blog, your ideas and designs are beautiful, I am also interested in design and construction ideas, but need help and work with people like you.

        • http://www.lifeofanarchitect.com Bob Borson

          Hi Muhammad,
          This entire site is designed to help people get a better understanding on what and why architects do what they do. Hopefully you will get the chance to explore the many, many articles that are on site.

          • tavana

            Thank you, Mr. Bob Hope with you what I’m supposed to get one in your mind.

      • brandyromano

        Thank you, I wouldn’t have thought it was the more expensive option. I also like the idea of a steel pier and beam foundation because the main reason I’m TOLD they won’t do them is termites. I’ve heard there is less waste with steel beams, but I haven’t found any companies closer than Austin that have experience with them. Have you been involved with any projects that involved them?

  • Melinda

    I recently discovered my home was built on footing w/pads stacked on & no piers were used at all . is this a normal practice ?

    • http://www.lifeofanarchitect.com Bob Borson

      if you have an older home – it’s not all that uncommon. I have crawled through many foundations under a house where the piers were built upon old Osage-Orange tree stumps (also known as “Bodark” or “Horse-Apple trees”).

      If you have a fairly new home (say after 1970) this would not be particularly common practice.

      • Melinda

        My home was just built 8mths ago also my piers are set 10 ft apart but I thought they should be 6-8 ft apart ??

        • http://www.lifeofanarchitect.com Bob Borson

          the spacing of piers is engineered based on the size of the structural members spanning between piers, 10′ apart isn’t necessarily an issue.

          However, I am confused – in your first comment you said there were no piers, but no you are saying there are piers but that they are spaced 10′ apart? What sort of pads are you talking about? Is it a perimeter grade beam with wood joists that occasionally have some sort of built up members underneath?

          Are you have problems? You should be warrantied against contractor defects for at least a year.

  • Art

    Excellent detail on how to design and pour a grade beam -appreciate your labor of love. The only comment I would add is the importance of keeping that concrete moist or wet for as long a period as possible. I am surprised at how often I see poured concrete kept wet or covered for a day or two and then allowed to dry or bake in the hot sun. While I was at tech school (40 years ago) we poured cylinders of concrete and after they had set up we allowed some to just air dry, some were set outside in freezing weather after a few days of curing and others we placed in buckets of water. At the end of the course we took those cylinders and placed them in a press and applied pressure until they broke. The ones placed under water were incredibly strong compared to the others. The ones which had frozen were very weak. We were told, and I believe it from experience that as long as concrete is kept moist and not allowed to dry out it will continue to cure (get stronger) indefinetly. Yes concrete will reach its design strength if kept moist for 28 days, but the longer the better.
    Thanks again for your excellent document.
    Art Isted

    • http://www.lifeofanarchitect.com Bob Borson

      Hi Art, thanks for sharing!

  • Jackie Vargas

    Haha! Fun read! Love your sense of humor and natural style for such a topic. Great post.

  • Wendy

    We are building a lake house in Alabama on a pier foundation due to ground requirements for septic system area that must be beneath. (Had a hard time with perc test; ground is rocky, mostly shale and steep grade to the water.) Would you suggest poured concrete piers in this situation? Any other advice or concerns for us? Footprint must be 64’x38′. Thank you!

  • Jerry

    Don’t know if this is the right place to ask the question, but building a concrete pier foundation for a 16×24 foot studio, have the option of 12 piers and 10″ sonotube (spaced 8 feet apart width and 8 feet apart length) or 9 piers and 12 inch sonotube (spaced 8 feet apart width and 12 feet apart length). I prefer the 9 piers (less labor and I can use 2, 12 foot 2×10 girders, butted over the middle pier.

  • Tim Warner

    I have a approx. 1800 sq. ft. ranch style home in SW Arkansas. It was built in the mid 80’s. It is a pier and beam with a dirt crawlspace. I have the usual issues with the winter and summer expansion and contraction. There are small cracks where sheetrock walls are pulling away from the ceiling and doors that no longer seam to fit. The crawlspace is bone dry and all the cinder blocks and floor joists look new. A contractor told me that all I need to do is add more footings and piers to keep the house level through the seasons. Have you run up against anything like this?
    Tim Warner

  • Steve

    Don’t know if this post is still alive but if so I have a question. I am having a house built in an area of Texas with extreme soil movement. My contractor tells me that in order for him to be able to provide a guarantee on his workmanship he must put in a barrier beam around the slab on dirt foundation. I have never heard of this but he claims to have done several. Down side is the cost doubles that of a regular slab. Any thoughts?

    • http://www.lifeofanarchitect.com Bob Borson

      I’ll admit that I am not familiar with the terminology “barrier beam” but maybe that’s not surprising as I don’t do a whole lot of slab on grade foundations. I was wondering if it was what we call a dropped edge where the slab basically thickens up into a grade beam around the perimeter of the slab. This still wouldn’t keep your house from moving – it would still lift up whenever there was soil movement but it would tie everything together and provide additional stiffness to the slab – this would logically require the lift to be a bit more substantial before damage was done because the slab wouldn’t bend (crack) as readily due to the thickened edge.

      Sorry I am not more familiar with your situation – wish I could be of more help.

  • Pingback: Modern Residential Framing | Life of an Architect()

  • Steve Bondy

    This is very informative!

    My wife and I are about to start design on a home in the Hill Country, and thinking in advance about some structural issues, I’d prefer a pier and beam over a slab on grade. However, in some research I did on the web site of a structural engineering firm, I found the statement “The most important thing to remember for pier and beam foundations is that if you live in an area with expansive soils (e.g. Clays), which is most of Texas, the building code does not allow you to use a pier and beam foundation unless the piers are deep.”
    Is that right? If so, I guess this foundation qualifies as “deep”?

    I’m also a bit worried about the builders knowing how to do one, but that’s another issue.

    • http://www.lifeofanarchitect.com Bob Borson

      On our projects, we have a soils engineer do a boring on site and they determine how deep the piers must be – not the contractor. On this project, we hit rock in some areas as shallow as 2 feet and as deep as 8 feet (neither of which is all that “deep”) The statement you quoted above is simply letting you know that piers have to be deep enough to go beyond the expansive soil until they sit on rock – which varies by region.

      Hope that helped. Good luck –

  • Tom

    Great post Bob. Very informative. I have read all of the posts below and I know you have been given those compliments several times. With me though, they are more than compliments, this post actually is extremely helpful. Let me explain why. I have found myself doing a drawing of an addition to a home with the same soil conditions, Clay, and with a similar pier and concrete beam construction. I have not been able to find anything on the net that was of any help. I found you through Chief Experts website with Dan Boumann. My lucky day.

    Some differences though, In my situation, the piers are constructed square on the perimeter and round in the field supporting wood beams. I have never come across this before. I have attached a picture. Notice how the beam is chamfered on the bottom and it sits on a square type pier that seams to have been poured in conjunction with the beam. So I am trying to draw something that will work.

    Also If you look at your last two pictures, it seems that the beam is sitting directly on the piers. Contrary to your drawing example.

    Now here comes the asking for a favor part. Is there some way I can get the details of these drawings from you? Beam size. The rebar size and placement in beam and piers. The cardboard spacing depth? I would greatly appreciate it. If not, this post has been most helpful in itself.

    Thanks again, and have a great day.

    • http://www.lifeofanarchitect.com Bob Borson

      Hi Tom –
      Sorry for the delay in responding, I hadn’t seen your comment until today. I don’t want to send out our actual details, seems like it could open me up to some sort of responsibility that I’d rather not take on – sorry.
      As for the placement of the beam relative to the piers, in my pictures and my sketches, the grade beam ALWAYS sits on the piers. There seems to be some slight misunderstanding of my sketches. The uncolored space you see in my sketch is supposed to represent the air space between the dirt and the bottom of the grade beam but if you look closely, the piers is sketched in (it is shown beyond in the section) and the lines carry up and all the way to the bottom side of the grade beam.

      Hope that clears things up for you

  • http://twitter.com/oakvillecabinet timraleigh

    Great post, answered a lot of the questions I had as I watched guys working on the slab for my brothers house in Huston. His was a post-tensioned slab on grade.

  • http://batman-news.com Billy Bob

    I like Frank Lloyd Wright’s description of pier and beam construction when he designed the Imperial Palace in Japan. He said it was like a waiter balancing a tray loaded with food on his finger tips.”
    Another favorite by an unknown source, ‘horse since is found in a stable mind”

  • Scotty Amen

    Highly informative, thanks for taking the time to explain all this.

    • http://www.lifeofanarchitect.com Bob Borson

      you bet – glad you liked it and found it useful.


  • Eric Whiting

    Always enjoy your posts.
    I’m curious about costs on this type of construction with say a frost wall design, which is the prevailing construction method for non-foundation residential in the Northeast.
    Also, is there an elevator in this house?

    • http://www.lifeofanarchitect.com Bob Borson

      no elevator in the house – all the rooms except for the secondary garage are on the same level. Since we don’t design frost walls, I can’t do a comparison. The other moving part on this particular foundation was the amount of rock we had to excavate to install – it was a lot and added to the overall cost of the foundation.

  • Amn

    Small point of clarification to your excellent article: in paragraph one, the differential movement of the soil due to clay expansion/contraction is the concern; if the soil under the whole site moved together, then no problem. It’s when one part moves and another does not that the fun really begins.

    • http://www.lifeofanarchitect.com Bob Borson

      rarely would the entire site move together so that isn’t really a concern. Parts of the house are sitting entirely on bedrock while others still have some soil under the grade beams – different conditions.

      • Amn

        That’s the point I was trying to make.

  • ParadigmGallery

    Bob The Builder was a favorite of mine so of course I really enjoy Bob The Architect…;-) You are a great teacher, drawings and images…fantastic!

    • http://www.lifeofanarchitect.com Bob Borson

      Thanks – I really appreciate the kind words and that you liked the post.


  • Robin R

    The photographs shown in your informative post don’t show vents in the foundation—which would classify this as an unvented crawl space. Is the crawl space conditioned? If not, how do you deal with insulation and moisture issues? I know this is the subject of another post, but living on the Mississippi coast I am very interested in best practices in dealing with these matters. Thanks…

    • http://www.lifeofanarchitect.com Bob Borson

      without getting too technical (because the answer would require more time than I have) this will be a mechanically vented ducted crawl space, but not a naturally vented crawlspace.

    • Amn

      Without mechanical ventilation, a crawlspace can be kept dry with a french drain around the outside perimeter and a vapor barrier attached to the inside face of the beam which turns horizontal across the crawlspace floor for a few feet. These two additions will reduce moisture migration from surrounding groundwater and counteract the natural ‘sump’ action of the lower level under the building.

      • http://www.lifeofanarchitect.com Bob Borson

        the entire crawlspace on this project has 2″ of gravel, a 10mil vapor barrier, and another 2″ gravel throughout the entire crawlspace. We also have sealed mechanical equipment so the intake and exhaust air servicing the equipment is ducted.

  • Dolores Browne

    Thanks for the info.

  • lindahelen

    Great post! Super informative and entertaining too!

    • http://www.lifeofanarchitect.com Bob Borson


  • Steve Mitchell

    Nice job. Learned something new today, (void form). Love the sketches too.

    • http://www.lifeofanarchitect.com Bob Borson

      Thanks Steve – that’s the best I could hope for – share something of value and created some graphics people appreciate. Win-Win

  • Ken Routh

    If you replace the words pouring concrete with placing concrete you will be
    be an erudite architect.

    • Kerry Hogue

      actually you pour concrete. afterwards it has been cast.

      • http://www.lifeofanarchitect.com Bob Borson

        (go UT)

  • Taylor

    Cool post! As a student, we do not see things such as this! Even trying to supplement my education during school with further research, I have not come across this yet… the sketches and descriptions were very well explained and it is great to see. Thanks for the post – I read them all! Question (unrelated to the content of the post, unfortunately) – I am assuming you used trace for your sketches, I am wondering what type of medium you used for the coloring? It looks great. Thanks Bob.

    • http://www.lifeofanarchitect.com Bob Borson

      I did the sketches on top of trace paper (like 90% of all my sketches) but I scanned these in and added some color in photoshop. It’s definitely a cheater way to go … but it needed the color to help the clarity of the information.

  • Rossco

    Its great to see this discussion,in the past we also used polystyrene sheets beneath the surface bed /floor slab(South Africa),it too would perish ,a void would remain to allow for the expansive displacement vertically.
    Construction and Architecture in tandem,its a winner when designing and making sense of the practicality of a building technique.
    Looking forward to the flat roof detailing and insulation.

    • http://www.lifeofanarchitect.com Bob Borson

      hopefully I won’t disappoint on the flat roof posts ….

      How long does it take for polystyrene sheets to perish? Doesn’t that stuff have a half-life of like 500,000 years (or something)?

      • Rossco

        mmm… good question, not the most enviro friendly stuff either-probably just took up the movement depending on the expansive properties-its going back a few years in the days when butter was good and margarine bad(or was it the otherway round?), the cardboard option makes more sense.

  • Elrond Burrell

    Great explanation, well illustrated in words & pictures Bob!

    • http://www.lifeofanarchitect.com Bob Borson

      thanks Elrond. Simple is never easy is it? … unless it’s a yurt.

      • http://elrondburrell.com/ Elrond Burrell

        Hmm, I’ve never put up a yurt but it doesn’t strike me as being that easy! :-)

  • Tim Barber

    I’ve never used them before either, but makes perfect sense to me! You architects need to learn somethings! Push that dirt back up under that beam, NOW! :-) I guess architects are a couple of levels below a home inspectors?

    • http://www.lifeofanarchitect.com Bob Borson

      I don’t think anybody is better than me, apparently it’s just that I know some things that others don’t.

  • Gene Drysbach

    Great post. I’ve never seen that used. In PA

    • http://www.lifeofanarchitect.com Bob Borson

      wouldn’t it be great to be the first? Leader of the pack!

  • michael

    interesting post! longtime reader first time poster. Blog is great. Question: is the cardboard “rotter” a pre-made item or site made? and if you have one please post an addendum pic of it – Thanks!

    • http://www.lifeofanarchitect.com Bob Borson

      It is pre-bought but they cut it to length on site. They also wrap it in plastic to the wetness of the concrete doesn’t speed up the rotting process. I have a picture here of a trapezoidal carton, but they come in versions that have straight sides to them as well. If you use the trapezoidal ones, the concrete from the grade beam fills the angular void which makes having soil retainer boards unnecessary. We have some of these on this project but we also have the rectangular carton forms as well.

      Hope this clarifies things –

      • Kerry Hogue

        they come in different widths and depths as well for different thickness of grade beam and expansion accommodation. once the forms are removed the plastic envelop is punctured to allow the carton form to collapse.

      • michael

        Thanks Bob – very interesting. Such a simple yet effective technique.

  • Reggie Konet

    Very informative post, Bob. Keep these coming!

    • http://www.lifeofanarchitect.com Bob Borson

      I’ll do my best.


  • Steve

    This is interesting and seems like a simple foundation system, up here in the N.E. it’s footings and frost walls 4′-0″ below grade, I’ve never had the opportunity to use this t

    • http://www.lifeofanarchitect.com Bob Borson

      We don’t really have to deal with frost lines down here … with the bad comes some good.

  • Scott

    No rebar caps? Limited PPE for the cement crew? I see a lot of bare hands touching wet concrete, and concrete burns are no joke.

    • http://www.lifeofanarchitect.com Bob Borson

      I rarely see rebar caps on residential work down here – commercial yes, residential no. These concrete guys are hardcore – they work together in very tight knit crews and stay together for years. They never complain, they show up everyday, eat together on site, and train the new guys. The head foreman on this project was certifiably a genius, the stuff he could visualize and the math he could perform in his head was unbelievable.

  • Dzintars Berzinskis

    Can’t wait for next post like this, who knows what type of “vegetable” you will share with us next time 😀

    • http://www.lifeofanarchitect.com Bob Borson

      that’s right – gotta eat those vegetables!

  • Bobbi Roberta O Amico

    I just glanced through for now – will read later….Thanks for sharing! Can I use this technique in Southern Az @ 4,000′ instead of a stemwall?

    • http://www.lifeofanarchitect.com Bob Borson

      stem walls – at least my understanding of the word and how we use it here, serves a different purpose than a grade beam. It’s probably best to consult with a structural engineer in your region whose more familiar with the construction techniques intrinsic to their skill set.

  • Jacob

    Very informative. Thanks for these more technical posts.

    • http://www.lifeofanarchitect.com Bob Borson

      Thanks – they’ll come more frequently now that the house is out of the ground. It takes so much time to do the foundation and there isn’t a whole lot to cover without getting crazy technical. Now that everything else will begin, there’s so many things to show.

  • Cathy, RA

    thanks for the informative photos and sketches! i’ve heard about the negative space under the footings for expansive clays in Texas, but never understood it until now.

    • http://www.lifeofanarchitect.com Bob Borson

      Glad I could explain it in a way that made sense – I was worried that despite the sketches it would still be confusing. I even thought about doing a video thinking that it would be so much easier to explain. I decided that I would rather get some sleep.


  • Julia Craighill

    Brilliant. Your posts are a great way to start the day. Keep it up!

    • http://www.lifeofanarchitect.com Bob Borson

      Thanks Julia – feel free to leave these sorts of comments all the time. Makes it more worthwhile as I sit on my couch at 11:00pm trying to get them written. :)


  • Lora

    So if you put the AHUs in the crawl space in expansive soil, do you have to allow for extra space from heave under the floor joists/slabs, just as you do under the grade beam?

    • http://www.lifeofanarchitect.com Bob Borson

      Good question – we will at most experience a few inches of heave and I’d say that there is about an extra 14″ clear from the ground to the underside of the hanging AHUs. They will not be at any risk.

  • Doug Kuchta

    Sometimes you honestly make me want to quit my firm, and move to Texas to work with you/ your firm. I hope your staff know how lucky they are. Awesome post!

    • http://www.lifeofanarchitect.com Bob Borson

      Thanks Doug, pretty sure they don’t have the same enthusiasm that you might think but I generally think people like working with me. If they didn’t, I could probably work a lot less hard at it!

  • AlmostJane

    Your home inspector anecdote is disturbing. Really makes me wonder how many other inspectors are out there telling potential owners they have – or worse, haven’t – got problems of various kinds. Reminds me of that George Carlin routine about the fact that we need to remember that every med school class has someone who graduated last. And one of us has an appointment with that guy at 9 am tomorrow morning.

    • http://www.lifeofanarchitect.com Bob Borson

      I love that bit from George Carlin … it will ALWAYS be funny.

      I pointed out to my doctor that her license said that she met the minimal standards required to practice medicine as determine by the AMA (or someone like that). I asked her why they felt the need to phrase it that way, it wasn’t necessary. Next time I came into the office, they were off the wall.

      • AlmostJane

        No kidding? Well, THAT’S interesting. And yepper – that bit will ALWAYS be funny. :>)

  • Branson Young

    never met a home inspector I liked. If its not slab on grade with spread footings (atleast in this part of the country) they dont seem to understand. I had one instruct me that I had to install almost 260lf of retaining wall down the sides of my property because I had erosion issues. I had a Civil Engineer friend get involved and the real issue was that the neighboring property was eroding onto mine. A little bit of grading and some sod and the problem was solved. Frequently they make mountains out of molehills…suppose its a form of CYA.

    • http://www.lifeofanarchitect.com Bob Borson

      I take it all with a grain of salt. I’ve no doubt they have good intentions – it just doesn’t always work out that way. 260lf of retaining wall would have been a nice chunk of change, glad you were able to avoid it.

  • Zack Alsentzer

    Impressive. Thanks for sharing.

    • http://www.lifeofanarchitect.com Bob Borson

      Thanks Zach!

  • Tina Ryan

    Home Inspector: “Son, I’’ve been doing this a long time”. His attitude reeks of abusive parental authority – bet he thought you needed a walloping too.

    • http://www.lifeofanarchitect.com Bob Borson

      Since I’ve had white hair since my 20’s, I haven’t had to deal with this sort of thing too often. It is such a diminishing sort of comment, it’s my indication that there will be no constructive conversations in my future with this person.

  • Kerry Hogue

    good stuff Bob. I had a similar discussion with a home inspector, but on a house I was selling. I asked to see his PE license.

    • http://www.lifeofanarchitect.com Bob Borson

      kind of kooky, isn’t it? In this area, you would think they would have a better grip on this system.

  • Alan W

    Killer post! You must be beaming with pride about this house! I usually avoid being pedantic, but there are a couple of typos in the copy. I hope you take that as constructive support, and not a concrete slight. Puns aside, I really enjoy all the stuff I learn from you, thanks for getting technical!

    • http://www.lifeofanarchitect.com Bob Borson

      Thanks – but there are always typo’s … that what you get when you write these things right before you go to bed and hit ‘publish’. I generally go back and fix them the next day after I’ve given my brain a chance to step away from what I wrote.

      Glad you liked the post, it was a really long one.