Masonry Fireplaces – Cottonwood Modern

January 28, 2013 — 12 Comments

I am trying to keep pace with the progress that is going on at the Cottonwood Modern house but ironically, it’s going so fast that I barely have enough time to put together some information before it gets covered up.

I thought I would try to introduce you to the fireplaces we have on this project – sounds pretty formal but really this is about seeing what’s behind the wall rather than  just the finished version of the fireplace that you might see in your favorite shelter magazines. Eventually, I’m sure I will get around to having a few finished photos of the final enclosed fireplace, but not today.


Fireplace in the Great Room 02

The fireplaces we are using on this project are all real wood burning fireplaces, although I’m not sure how much real wood is going to be burned indoors. In all, there are 4 fireplaces on this project – two are located inside the home (in air-conditioned space), one is located in a covered exterior patio, and the fourth is being built out at the pool pavilion. All of these fireplaces are pre-manufactured kits produced by Isokern – a Danish company that uses Icelandic volcanic stone to form the individual pieces – shipped to the site disassembled and put together on site by the masons. The fireplace in the picture above is located in the Great Room and is low and wide. It’s hard to tell the scale from this photo (since there are so few things to indicate size) but the clear opening where the fire will burn will is 6′-0″ wide and approximately 20″ tall. Part of the reason we are using Isokern fireplaces on this project (on most of our projects actually) is that we like the scale of the opening where the fire will be built.


Fireplace in Game Room 01

This is the fireplace in the Playroom  and is a better indication of a typical fireplace opening – 3′-6″ wide by 4′-0″ tall.


fireplace in the covered patio

This is the fireplace that is located in the covered patio. Since I tend to do some of my job site visits on the weekend, I had my daughter with me and she was kind enough to agree to sit in the fireplace for me to provide some scale. (How do you like her job site shoes?)

One of the reasons we really like using these modular fireplaces is that they are quick to install (generally less than a day each) and  are very cost-effective. Each one of these fireplace kits, plus installation, runs approximately $5,500. Pretty good for true wood burning fireplace of this size.


Fireplace flue in Game Room

One of the things that we include on all of our chimney installations is a fresh air intake. In the houses that people my age grew up in, there were air leaks throughout a typical house – windows, doors, through vents – I’m talking air leaks everywhere. Things have changed and while we don’t really consider air leaks to be a good thing, it did allow for those old fireplaces to draw air a lot better. This meant that when you burned a fire, the smoke went up the chimney and not into the room where the fireplace was located.

Since modern homes are constructed much tighter than they used to be, the fireplaces don’t draw as well. That’s where the fresh air intakes come in. If you look at the picture above, you can see on the left-hand side, the small 3″ flexible metal flue. This is where we get our fresh air.


fresh air intake on interior of assembly

This is what the fresh air intake looks like in the fire-box. Pretty small and located at the bottom of the fire-box, there is a sliding vent that you open when using your fireplace that draws air from outside to feed your wood burning fire.

Yes, it’s that simple and we have recently started to see municipalities making the installation of these intakes mandatory. We weren’t required to install these in the city where the Cottonwood Modern house is getting built, but we think it’s a good idea so it has become a standard detail in our office.


fresh air intake on exterior of assembly

A look at where the metal flex pipe enters the fire-box from the side – it isn’t pretty but it gets the job done and you’ll never see it once everything gets put in place.


Fireplace brick herringbone pattern

In all of the fireplaces we have 4″  wide x 9″ long x 2″ tall cream splits in a herringbone pattern … except the fireplace in the Great Room where we have a running bond pattern to accent the horizontality of the fireplace. “Splits” are basically solid bricks  that are laid on their edge with a minimal amount of mortar and they are responsible for providing a decorative finish to the interior of the firebox and also acting as a refractory – pushing the heat back out into the room. These splits come in different colors and cost around $1.60 per brick.


Fireplace in the Great Room

I thought I would end of this post with a look into the Great Room. This is a large room and a regular sized fireplace would have looked ridiculously small in here. The end of this room – the part that is completely open in this picture – shall remain open as this is one of the cantilevered glass boxes with floor to ceiling glass.

Should be pretty nice when it done.






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  • Marie McKeige

    Thank you for sharing. Beautiful fireplaces.
    I have a question.
    We are building a home in the Adirondack mountains of New York State and have a local mason doing the fireplace. I am in favor of the herringbone pattern, but the mason is insisting that because the upper section of the firebox will tilt slightly towards the opening (not a very steep angle) we can not do the herringbone pattern as it will not be supported enough. He says we have to stick to the traditional running bond pattern.
    I do not see what the difference in support is between the different patterns.
    Any suggestions of how to approach this?
    I might have my own answer…why does the upper section have to tilt back towards the opening…

    • The back of the fireplace will tilt forward – towards the front of the fireplace – not back. And the bricks that get used are a special size and not the sort of bricks you use on the outside of a house. I can’t think of a reason why you couldn’t have a herringbone pattern. I’m not a mason so I can’t dismiss the fact that I don’t know everything.

      • Marie McKeige

        Thank you Bob, and yes you are right, it tilts towards the front. I think I was trying to say that it tilts towards the front…except I called it the opening.

        This is why you, an actual architect, is so much better at communicating.
        I am attaching visuals of our project.

  • Jeremy Sahlman


    i am putting an isokern in my house I am building and kind of hate the look of the air intake kit they supply. I was thinking I would fashion my own out of an antique cast iron heating registry Any thoughts or concerns about that? tips on installation of those guys?

    also what types of damper are you using? the isokern inline eDamper? I can’t seem to find any literature on how it works

    thanks for any help / advice.
    Jeremy from Maine

    • since these are all wood burning fireplaces, they are required to have a damper and when we specify the model we want to use, the damper is part of that component. I went back and checked on the invoicing when the statement came in from Earthcore and it simply stated (on our 42″ Rumford style fireplace): DMPR42 – Damper Cast 42″

      As far as using a antique cast iron heating register – I couldn’t tell you. Getting fireplaces to draw properly is a science and I don’t like to stray too far off the rails when designing them.

      Hope this helps.

  • Hi Bob,

    Love your blog, always great, fresh content, thanks for all you do. I was very interested to read about your experiences with Isokern as we do many masonry fireplaces in our projects and this seems like a great cost effective alternative to the more traditional method. I wonder about the fresh air intake on this project. We typically design to the IRC and that prohibits the exterior air intake from being higher than the firebox, is there any concern with the potential for it acting as a secondary flue? Thanks again, really outstanding work, always interesting. -Eric

    • Hi Eric,

      Since the total amount of flue space above the fireplace exceeds 32″ is diameter (there are two large flues) I am not worried about the 3″ flue set at the floor of the fire box acting as a flue.

      Good question though.

  • Personally I find it outrageous that apparently it’s no problem to run around in shorts in the Dallas area in January (!!!) – or are those old fotos?

    • Hi Jan,
      That photo of my daughter was taken yesterday – January 27th. Currently it is a mind-boggling 77 degrees outside – I wish it were a little colder.
      Fireplaces in Dallas are fairly common but they aren’t used for generating heat in the room – it’s more about creating an atmosphere that speaks to “home” – or at least most people’s idea of home. We will have air conditioners providing heating and cooling as well as radiant heating in some of the bathrooms. While it rarely gets freezing cold here we do have periods in the low 30’s and 20’s every winter.

      Good question!

      • Jeanine H

        Just a quick question: you say you’ll have “radiant heat for the bathrooms”–are you going with floor radiant, panel, ceiling? Just curious as to what you’d decide? We’re having heating issues in our basement and haven’t decided which approach ceiling floor or wall panels?…just wondering what type of ‘radiant heat’ source you’ve decided on? personally bathrooms I wud go with floor.
        Jeanine 😉