A client of mine wants to add exterior insulation over wood siding and cover with vinyl. I don't think this is the best option but am looking for some feed back. The house (cottage) is a 1974 2x4 800 sq. ft. bungalow.
Another option is to strip off the old wood siding and add additional exterior insulation and then the vinyl. Apparently this would require long nails (about 3 - 3 1/2") but I have also heard that the siding might sag as the foam insulation has little holding power to support the length of the nail, even though they would penetrate the siding, foam, and hit a stud.
Any suggestions, advice is welcome.
Yes can install vinyl sidng over wood siding provided that the walls are straight.
Leave the wood siding on, this will act as a insulator. Strap over top of the wood siding with strapping, 1x4 @16" centers would be good enough. Install dense styrofoam insulation board between the strapping and then the vinyl product.
You may have to frame out around doors and windows to bring them out to meet the siding. It works good
It is highly recommended that you remove the siding to not only work with a smooth surface; however, to also inspect the building envelope for irregularities. Ensuring that windows and doors are properly sealed and flashed, ensuring continuity of the building envelope, and inspecting the substrate construction (most likely plywood) for rot and decay.
To answer your second part, 1-1/2" rigid insulation will work with 3-1/2" nails and the siding will not sag if properly installed. Refer to your supplier/manufacturers specs on nailing requirements.
I hope I helped you with your questions!
Never go over old siding!.... strip it down to the sheathing, check it, add your strapping, reflash, seal.
I like to actually seal or waterproof the surface when adding foam, strap it and add your insulation and vinyl or better yet insulated vinyl if the customer wants to spend 35 -40% more for the additional R.
All recommendations are valid. It boils down to price and customer expectations. The better you prepare surface the better siding will look 10 - 20 years later.
As to nailing through the insulation I never had issues with panels up to 1", make sure you do proper nailing at no more than 16".
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