Build Your Own Sunroom

The first challenge was the roof for my sunroom. After considering various options, I decided to go with corrugated  fiberglass-reinforced  plastic (FRP) panels. They come in 8' x 26" sheets, are lightweight and relatively inexpensive - I paid $16 per sheet at a local building supply store. I opted for clear (i.e. not tinted) panels, as I wanted to maximize the light. One mistake I made was using 4-ounce, rather than stronger 8-ounce panels. While a bit more expensive, I think it would have been worth it in the long run. 

 I also considered vinyl panels - they're a bit cheaper but not as strong, and are prone to fading and degradation (becoming brittle). And the Cadillac of corrugated panels are those made of polycarbonate, the strongest material available. But they are twice the price of FRP. 

Another consideration is the cost of the requisite spacers needed to install these different types of corrugated panels - strips of foam, plastic or wood installed underneath the panels, between them and the roof joists and cross-braces. These allow the screws to be placed on the top of the ridges (to prevent leakage at the screw holes), and to provide support. Purchasing all of these spacers could easily cost as much as the corrugated panels, so I made my own. Using the FRP panels, with their rounded corrugations, this was a relatively easy task. However, the polycarbonate panels have a more squared corrugation profile, which would make the spacers more difficult to cut to the proper shape.

Another option I thought about for the roof was using glass, but I wasn't sure I'd be able to find enough panels, and was concerned about sealing the seams. Weight could also be an issue. I also considered shingled plywood, with 2 or 3 skylights, but then my sunroom wouldn't have been as bright, and the cost would have been significantly higher. 

This is what the spacers look like. They are the wavy strips on top of the 2x4 cross-braces. Another spacer runs lengthwise along the top of each 2x6 ceiling joist, which I made from 8' 1x2's, rounding the top edges with my router.


All of the lumber used for my roof was untreated 2x6's and 2x4's, which I painted prior to installing (it is much easier that way). To attach the roof to the house, I first lag-bolted two 10' long 2x6's to the fascia board, end to end, just below my rain gutter. This gave me a 20' long ledger board, on which to hang my 2x6 ceiling joists. 

The outside header beam was a bit more complicated. It had to be high enough to accommodate my sunroom wall (standard patio door height of 82"), but low enough to maximize the slope of my roof, facilitating rain water run-off and reduced snow loads. For support posts, I used four treated  4x4's, cut to 92" and bolted to the front of the existing 2x6 framing running along the front of the deck.

Before installing them, I notched the 4x4 posts at the top, and once installed I lag bolted the 2x6 header beam to these four posts. It was actually comprised of two 10' 2x6's, that I cut so that they would meet at one of the 4x4 posts.

Once my ledger board and header beam were in place, I could install the ceiling joists. I used joist hangers to attach them to the ledger board at the house end (see picture above), and something called a hurricane bracket to attach the other end to the outside header. I notched the outside end of the ceiling joist, to drop that end and maximize the slope. 

It's important to use straight (not warped or twisted) 2x6's, and to install them as level with one another as possible. This is so that they will line up with the corrugations in the FRP panels. Use of the hurricane brackets allowed me to adjust the outer end up or down slightly, in order to get each joist level with the others. Careful measuring ensured that they were straight. I spaced the joists 24" on-center, which allows the panels to overlap on each joist, preventing leakage at the seams. It's important not to allow the outside edges of the end panels to overhang the outside joists, which would catch the wind.

Next I installed the 2x4 cross braces. After doing some research, I concluded that due to the significant snowfall we receive here, I needed maximum support for the panels. For this reason, I sacrificed aesthetics for strength, and spaced the braces 16" apart. 

Now I was ready for the FRP panels. Starting at one end, I placed the first panel, slid the spacers underneath, and installed the screws. It's best not to try this on a windy day, as the panels can easily catch the wind and be damaged. I used siding screws, which come with rubber washers attached. I first drilled holes through the panels and spacers, to avoid cracking and splintering. I spaced the screws about 8" apart. except on the outer edges of the two outside panels, where I spaced them closer for added strength.

Each panel over laps the previous one on top of the joist and long spacer. I'm not sure if it was necessary, but I ran a bead of clear silicon caulking between the panels to guarantee they wouldn't leak at the seams. 

Once my roof was completed, I was ready to start on the walls