I want to install vinyl siding over my old siding which is soft in some places, probably rotten (I dont know how to determine, you can see attached photo). But I've heard that it's not a good idea to install a new over existed rotten. But what if I cover old siding with waterproofed home wrap before I install new vinyl? I think there will be no moisture anymore and I shouldn't have any problems. Is it a good idea?enter image description here

2 Answers 2


Is it soft enough that your nails will pull out? If your nails won't hold, you need to replace soft sections with OSB or plywood. Since you're covering the wall, it won't need to be pretty.

Follow manufacturer instructions regarding vapor barriers.

  • It is soft at some places in the bottom but it's good in general. But I can nail a new siding to the studs and it doesn't really matter how soft it is, right?
    – Rainmaker
    Commented Aug 6, 2019 at 20:02
  • No, your nailing pattern will be more closely spaced than that.
    – Valkor
    Commented Aug 6, 2019 at 20:03
  • Just tried to put a nail in it and I can remove it after with my hands from any part of my old siding without really big efforts. It means my siding is not good at all to put a new over it? Or I can use screws to make it more reliable? I just don't know how tight a nail should stay there, but its definitely not like in the wood, and my siding is not the wood, but smth else I'm not sure.
    – Rainmaker
    Commented Aug 6, 2019 at 22:30
  • I understand that nailing pattern will be much closer but each piece of siding will be attached at least to few studs, some nails will hold not very tight but some will hold properly. Is it gonna work?
    – Rainmaker
    Commented Aug 6, 2019 at 23:15
  • If by "work" you mean "stay on the house", then it will probably work for a while. If you want it to work for the time period the siding manufacturer says it should, then it won't. You will get pillowing and sags. Eventually, the nails that are solid in studs will break the flange on the siding, since you are concentrating too much load in too few holes.
    – Valkor
    Commented Aug 6, 2019 at 23:29

Vinyl siding over the existing rotting siding is not a repair. A repair includes replacing rotten materials with new. Removing the rotted material without replacement might be an alternative if the siding is not part of the walls lateral resistance system (for example siding backed by structural sheathing).

There isn’t really any form of good construction that involves leaving rotting materials in place. Rot does self heal.

Now is the easiest time to fix it. Everything is accessible and less damaged than it will be in the future.

In addition, fixing it now will make installation of new siding easier and the installation more sound. You won’t be dealing with failing new siding due to rotten substrate. Often this type of repair turns out to be less work than peoples imagine...even when the issues are worse than what appears on the surface.

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