Replacing masonite siding with vinyl

Old 06-22-07, 10:26 PM
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Replacing masonite siding with vinyl

I want to put vinyl siding on a garage that presently has overlapping horizontal masonite siding, some of which is deteriorating, and which has been installed right down to ground level. Do I need to remove the masonite first, or can I install vinyl overtop of the masonite? If that's doable, do I need to be concerned that moisture may cause the masonite to continue to rot or deteriorate beneath the vinyl once it's installed overtop? Is there any concern about mould developing?
Old 06-23-07, 10:43 AM
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I've found that the main problem with going over the top of Masonite lap siding is that it usually doesn't lay flat. The punky areas you refer to often stick way out and need to be knocked down flat. Some masonite has also developed buckles in it which will telegraph through to the vinyl if you just go over the top. When you install over lap siding you would first need to install fanfold underlayment, and that plus the siding usually builds the j-channels out past the windows which may or may not be acceptable.

Your point about it being installed close to ground level is probably the biggest concern, since it will still be prone to wetting and mold which could then also transfer onto the siding. I'd really suggest you remove it, since there are no drawbacks to removing it except needing to dispose of the waste.

After removing the Masonite, you'd want to ensure that there is a good layer of building paper over the sheathing. If the sheathing is in close proximity to the ground as well, a layer of ice and water shield 18" up across the bottom would be appropriate to help protect the sheathing from the same sort of damage that the Masonite sustained. If you'd like to bring the siding level up some, you could install a horizontal band of Azek around the bottom, or any sort of 1x6 or 1x8 and then have that covered with aluminum trim coil. That way your vinyl siding would be off the ground a ways. But obviously vinyl siding won't be damaged by ground contact. It will just get awfully dirty when it rains and splashes dirt on it.

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