I was on the KHouse Modern job site a few weeks ago and during our weekly Tuesday construction meeting, I mentioned to the owner that the oculus was just about to start construction. He looked at me and said “Oculus? What is that?” I told him that it’s basically an opening in the ceiling to let the light in, or as I like to call them – the “coolest things ever”.
An oculus is basically a round opening that is located in the center of a dome or wall. The most famous oculus is in the Pantheon, and while everyone who has ever been to the Pantheon remembers the oculus, few probably knew what it was called.
The Pantheon is a building in Rome, Italy, commissioned by Marcus Agrippa during the reign of Augustus (27 BC – 14 AD) and rebuilt by the emperor Hadrian about 126 AD.The oculus is a large opening at the dome’s apex and along with the entry door, are the only sources of natural light in the interior. Throughout the day, the light from the oculus moves around this space in a sort of reverse sundial effect.
If you have ever been to the Pantheon, you probably have this exact same picture, as well as the lasting memory of the impact the space had on you. This is still the world’s largest un-reinforced concrete dome and one of the most amazing interior spaces I have ever been in.
We have an oculus at the KHouse Modern and there have been a few occasions when I’ve wondered if anybody other than me remembers that it’s there. If you look at computer rendering of the roof plan (in the image above) you can easily see the round opening on the upper right-hand portion of the project. This is an exterior space – a space that exists between the main house and the detached guest quarters and basement level garage. This is the area that the owner will do all of his exterior cooking – protected but yet, not entirely protected.
This was one of sketches I created when I was studying this area during the design development phase. We have an average of 4′ deep overhangs that extend beyond the face of the house and when you add them to the depth of the grilling patio, I was concerned that this area would be too dark. So what do you do when you need to get some additional light into an exterior space that is covered by a roof?
You put in an oculus.
What?!? Did you say you put in an octopus??
Here is a look at the 3D render of the place where the oculus occurs. We went through a handful of studies to see exactly how the light would move through this space – one of the benefits to using 3D software – we were able to determine if this move would get us the results we wanted. An additional benefit to installing an oculus is that the light will now come into the space but there is still more than enough room to move around the area if it happens to be raining or some other sort of inclement weather.
We are still in the framing period but I wanted to show the beginnings of this opening so that once the project moves along, I’ll be able to follow-up with a more finished product post.
The process of building this oculus starts with building up the opening – which is made up of multiple layers of plywood cut to the correct radius. To achieve this, a nail is driven into the ground; a string is tied to the nail, and a predetermined length of string is then walked around in order to create the diameter of the pieces to be cut. In the picture above, you can see evidence of the radius that was marked out onto pieces of plywood.
Here is a pile of scraps left over from the process of cutting out the pieces.
The framers simply mark the circumference out onto a piece of plywood and then they are moved off to the side for cutting. They are numbered and stacked up for the next phase of the assembly process.
Once all the pieces had been cut out the assembly begins. They simply use the aforementioned template which was still marked out on the floor and start stacking the pieces one on top of the other. As evidenced by the picture above, you can see that everything is glued and nailed together.
The bottom and top-most layer of the cut pieces are joined together using a dado joint … I’m not sure that it’s necessary given that all the layers are glued and nailed AND that the joints between pieces (both on the same level and from level to level) do not align with one another, but I’m not complaining.
Once all the levels are put together, the framing for the oculus is lifted up off the floor to sand out any high points that were created as a result of building these framing members up out of several members.
That guy doing the sanding looks like he was tailor-made to sand stuff like this. Low center of gravity, internal vibrational control, elevationally specific vertical development. He did a great job.
At this point, the frames are rolled off to the side to await their use in creating an oculus at the KHouse modern. I am a bit anxious to see this come together in the framing – I’ll probably take a picture and through it up on my Instagram account well before the next post comes out. The owner of this house loves to give me a little business about this opening – I think he is amused that there is an actual name for an opening in the roof and that I refer to it as “The Oculus”. In fact, all the construction photos that are in this post were taken at last Tuesday’s standing construction site meeting and he made me sign the ring you see in the picture above. If I was more clever, I would have taken a picture of it at the time.
No worries, the owner and I know it’s there …
Cheers,
ps – I wrote the word “oculus” 17 times in this post – that’s got to be some sort of record
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What if I can make the Oculus on a solid Concrete roof? It will work?
of course – the Pantheon was made out of unreinforced concrete and it’s still here.
Great laugh from your description of the perfect sander professional.
Have you ever considered CNC milling for objects like the Oculus ring? you could map out all the parts and get a computer to cut the pieces into a sheet of plywood. I don’t know how much use the CNC mill would be to you but it may not produce as much waste as you have pictured above.
I don’t have any experience with a CNC mill but it seems like the right choice for the job or any other jobs you may think of.
I never knew what that was called but I admire the light!
My tutors used to call these ‘Moon holes’ there were a few in the roofs of the WISE building that they designed – our uni building. The big one in the roof of the circular earth rammed lecture hall resulted in an amazing space.
Interesting construction technique. I agree, not sure a dado (mortise) is necessary if the joints in the layers are offset and they use a good glue. It’ll be interesting to see how they frame around that. Thanks for posting.
What software did you use to examine the sun path and the effects on the project? I remember in university in Denmark we used Revit and it had in-built sun path shenanigans, quite cool, i don’t get to use it much here though, for now.
Based on the other posts I would guess Revit, but the same effect is easily accomplished using Sketchup and geolocating your models
OK, I have to ask the ‘not-an-architect’ question. Other than shape, is there a difference between an oculus and a skylight? PS – your description of Sanding Guy, smack dab in the middle of a more-or-less technical article? Fun-nee.
” … looks like he was tailor-made to sand stuff like this. Low center of gravity, internal vibrational control, elevationally specific vertical development.”
Wonderfully diplomatic language there – and I’m stealing it to describe myself the next time I’m asked !
As a builder of boats, I am very keen to see how you will accomplish that mmost tricky of jointry, of round to square.
someday you should up your game by adding a squinch into your oculus
definitely not enough squinches out there
or oculi
Another interesting fact about the Pantheon overlooked by most visitors are the bronze trusses holding up the pediment over the door. They are the earliest examples of truss construction remaining from ancient times. It would be several hundred years before trusses were again used to hold up a roof. Amazing!