Why not a round platform?
While a round platform can work alright for larger domes (4V or higher frequency), it is not recommended for our most popular 3V domes as the curve would stick out in between the hubs.
Follow our precision designed Exact Fit Platform Plans for the best results!
Deck Blocks and Runners
- These are the bottom supporting structure. Please note that the runner structure has less sides than the upper joist structure - this may seem strange, but it saves material, time, cuts, and deck blocks, while supporting all sides of the joist structure!
- If you find this confusing, you may modify the runner structure to have the same outer measurement as the joist structure.
- They are cut out of treated 4x6 beams. If you cannot find these at your local building supply, a triple layer of 2x6 lumber will also work like in the picture below.
- On level ground, the runner structure can rest directly on post saddles on the deck blocks.
- On sloped ground, you will need to use posts or screw piles in order to build up the support structure.
Use post saddles on top of the deck blocks - they will need to be larger
than the beams to accommodate for the angle
Use simpson strong ties on the corners and joist hangers where the
joists meet the perimeter.
Now we are coming to the most confusing part we always get asked about: How does the bottom layer of plywood sit on the runners? The answer is - it doesn’t. It is attached to the underside of the joist structure.
Build your 2x6 joist structure according to the plans and cut list, using joist hangers and tie plates. Then slide the plywood underneath piece buy piece with some help and screw it into the underside of the joists from the bottom.
You may want to build the joist structure in sections to
make this easier.
It may make sense to build the joist structure in sections so that it is easier to attach the plywood to the underside.
Once all the bottom plywood is in place, trim the edges and you can place the insulation batting between the joists. We recommend Rockwool as it is more resistant to moisture and critters don’t like to live in it.
The bottom plywood provides more
structural rigidity, however we have seen
people use hardware cloth (fine, rodent
proof stainless steel mesh) on the bottom
to hold the insulation as well.
At this point you will also want to make sure that all your services are in place - plumbing, wiring, ducting etc.
Lay our the subfloor 3/4" plywood on the joists according to the pattern on the plans and screw it down. You
may want to use wood filler in the cracks.
Tip: for a low-budget yet beautiful floor, you can use a tiger torch to lightly burn the plywood and bring out the wood
grain, and then apply a couple of layers of clear flooring finish to seal it. Please make sure to do this BEFORE you set
up your dome so it doesn’t light on fire!
Foundation Considerations for ExactFit Platform Plans
Our ExactFit platform plans are designed with concrete pier blocks, which require level, firm ground for proper installation. If your site is uneven or has challenging terrain, you may need to modify the foundation accordingly:
- Sloped Ground: Use posts under the deck corners to level the structure.
- Rocky Terrain: Consider poured concrete footings for added stability.
- Soft Ground: Screw piles provide a secure and adjustable foundation.
For site-specific recommendations, consult a local builder or engineer to ensure the best foundation for your dome.
Weatherproofing your Dome
Start by stapling the cover skirt to the outside edge of your exact fit platform. With the removable panorama window, you will not want to staple the skirt below the window. You could apply sticky velcro tape to seal it and still be able to open it. We have found a type of PVC trim on a roll (shur trim wall base at home depot) useful for both the outside and inside edges of the dome. You can staple or screw it and caulk the screw holes.
