Getting our root cellar walls built was a huge accomplishment, but now we are moving on to the more complex roof. We did so much research to figure out the best way to accomplish this portion of the project and I am happy to say it has turned out beautifully.
To start with we needed to build a wood form to hold the cement up until it had a chance to cure. A flat roof is a bad idea in a root cellar because there can be condensation. If it is an arched roof, it will not only have any moisture drip down to the sides, it will also be much stronger.
cut plywood
We started by cutting our 1/2 inch plywood into 8 foot long 11.5 inch strips. We did them this size so we could fit 4 on each plywood sheet and it ended up having a nice arch to it at this size. We then marked the center and cut a 3.5 inch deep, 1.5-inch wide notch out of the top for the backbone. We then used a section of wire fencing to make our line for the arch we placed it 1 inch up from the base at each side and had it arched up to the top of the board and I drew in the line. We then used a jigsaw to cut out the arch. After we created the first one we used it as a template for the other 8 so that they would all match.
dado blade
We then used a dado blade to cut in a 3/4 inch notch in (9) straight 10ft 2x4s.
grooved 2×4
The arched plywood fit nicely in this groove. These needed to be marked and cut for their specific location in the cellar as there were slight variances in the walls and we wanted a snug fit.
posts with top runner
We also needed to measure and cut (2) straight 16ft 2x4s for the length on the sides specific for each. These runners are what we placed our arches (inside the grooved boards) on. We also measured each vertical post location to position the edge of the arch at the edge of the wall. We then cut them to fit. We made (5) 4×6 posts on each side.
arches set across the center
After placing the posts upright with the runners on top of them we placed the arches up to connect the two sides. Placing the grooved boards across ties them together and helps provide a little stability. We had already placed the plywood inside the grooved board but if I could do it again I would wait until later. We had a few posts fall before we had it all put together and that was a little scary.
place in spacers
The next step is to place spacers between the arches to keep them from moving. It was a little hard to make this frame because the whole time we were very aware of the fact that we would need to take it back apart from the inside. After the spacers were in, it started to feel more solid.