We’re ready to replace all of the panels, but we don’t want to have to replace the entire room. Any suggestions?
A: From the picture you sent, it appears the roof panels are the type of multi-wall polycarbonate used to make greenhouses and other structures. Even if your conservatory roof has a different product, you can probably retrofit it with this material. And if you need to replace all of the panels to maintain a uniform look, know that polycarbonate sheets have an expected lifespan of around 15 to 20 years, so you might have to get the job done soon even if the knots hadn’t come up the plates fell.
Double wall polycarbonate is manufactured with square or rectangular channels placed side by side with the boxy shapes visible at the sheet ends. Erleen Trowbridge, retail manager at the Polycarbonate Store, a division of Charley’s Greenhouse & Garden (888-977-7659; charleysgh.com), looked at the picture you sent and said she is sure this is the type of material on your conservatory roof.
But she also said she wasn’t sure the original panels were installed correctly. The channels should run in the direction of the slope, with supports between the pieces. But even long slopes need transverse support at regular intervals. Judging by the picture, your sunroom’s panels were either installed with the channels running across them, or they have no cross support.
Trowbridge emailed the Polycarbonate Store a “Building with Polycarbonate 101” handout that explains the support structure required when the panels are used for cladding and roofing. Wood, PVC pipes, aluminum and steel are mentioned as suitable frame materials. They say the walls have polycarbonate supports, but let’s hope the polycarbonate is just a cover over the joints and that the frame is one of the stiffer materials.
Polycarbonate gets part of its dent resistance (it’s bulletproof at the right thickness) from the fact that it will flex when hit by something like a branch. Acrylic, which is also a clear plastic, is much stiffer and more brittle, making it more likely to break. Being flexible, polycarbonate must be supported with an adequate framework when used to cover walls or roofs. According to the handout, roof and wall frames should be no more than 24″ to 24½” centerline to centerline. And a crossbar between these supports should be installed at least every four or six feet, when the rafters rise from the eaves to the ridge; Walls higher than two meters also need transverse supports.
If your roof does not have cross-locking or if the panels were installed transversely, have a contractor discuss possible upgrades before purchasing new panels. Suppliers can generally provide technical advice and your local building department can discuss what is required to withstand snow loads or high winds.
Once you’ve made sure that buying new panels would be wise, there are a few things to consider. First, while it’s relatively easy to cut panels with a fine-toothed blade on a circular saw or table saw and join panels side-by-side, you don’t want transverse seams as the panels go down the roof. Home Depot sells 24″ x 96″ multiwall polycarbonate sheets that are just over ¼” thick for $44.98.
In specialist shops you will find longer, wider parts as well as versions that are thicker, insulate better or produce a clearer roof. The Polycarbonate Store, which ships nationwide, stocks four foot wide sheets in various thicknesses and in 8, 10, and 12 foot lengths. (Pieces up to 24 feet long can also be ordered by special order.) Prices start at $65.60 for panels similar to those that Home Depot sells but twice as wide, rising to $225.60 $ for 12-foot pieces of Super 5X-Wall. has cross bracing in the channels for extra strength where snow and wind are a big concern.
For a situation like yours, a 16mm TripleWall ($216 for a 12ft piece) might look best. It’s more transparent because it has wide channels that give more clearance between the sidewalls, and it insulates well because it has two layers of those channels, trapping more air.
You’ll also need an assortment of accessories, including materials to keep bugs and moisture out of the ducts, trim pieces to cover where the panels meet, and screws with neoprene washers to hold the panels to the frame. Specialist providers offer a wide range of these.
You will find numerous providers of multi-skin sheets made of polycarbonate online. In the DC area, one option is Polymershapes’ Jessup, Md. office (301-604-3623; polymershapes.com), which has different locations.
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