Hey everyone! I'm currently tackling a project where I'm planning to remove a fake chimney from my house, which is about 40 years old. I'm working with a handyman and need some advice on the siding. I have plywood siding, and I'll need to replace around 40% of it on the back. Underneath the plywood, there's a layer of rigid stryfoam. To give you a clearer picture, the structure from the inside out goes: Drywall - Plastic Vapor Barrier - Fiberglass - Rigid stryfoam (with foil) - Plywood T1-11. Given this setup, should I go ahead and pull down all the siding and stryfoam to replace it with high-quality plywood (maybe Zip) and new siding? Or is it enough to just replace the damaged areas? I'm unsure if the style of this building, which isn't very common anymore, warrants a full replacement or not.
3 Answers
Your wall's looking decent overall, but I'd recommend using unfaced polystyrene when replacing any insulation, since it allows for better airflow. For a solid job, go ahead and staple some Tyvek over the plywood sheathing with taped seams. Adding vertical battens will help hold the siding off the wall for circulation and drainage. Think of Tyvek like Gortex for houses—it’s breathable and keeps out wind and rain, which is great for protecting your plywood.
Honestly, don’t overthink it! Just make sure it matches the rest of your house. If only part of it needs replacing, just do that and keep it simple.
I get your concern! Just to clarify, the T1-11 is acting as the sheathing here, which is a bit unusual. Since the outer ply is only half an inch and the foil poly is older, you might want to consider that it can suffer from dry rot. If you end up having to open things up, it’s a good idea to replace the old polystyrene, especially if it’s nearing 40 years and is showing signs of wear.