Is a plywood subfloor with outdoor carpeting glued on appropriate for


We have a 20 year old screened in porch that had a plywood subfloor with outdoor carpeting tacked on. We just pulled the carpet up and noticed blackish areas - mold? The porch floor does get wet occasionally when heavy rain blows in through the screens. We wiped the plywood with a bleach solution. Installers are scheduled to come next week and glue down new outdoor carpeting. My question is, should the plywood be treated, stained, or painted prior to gluing down new outdoor carpeting? The porch has glass window inserts for the colder months, but we leave the screens in for the summer so the carpet will get some rain on it.

I will include pictures of the porch with the old carpeting and with the carpeting pulled up.

is a plywood subfloor with outdoor carpeting glued on appropriate for

Porch with the 20 year old carpet

is a plywood subfloor with outdoor carpeting glued on appropriate for

Plywood subfloor (mold or just dirty?)

  15 answers
  • Michelle Leslie Michelle Leslie on Aug 02, 2022

    Hi Josephina, I would get the subfloor checked out first. Mold can be hazardous to your health. Here's an article that will give you more information -

  • Seth Seth on Aug 02, 2022

    Yes, most likely mold. Bleach will not kill mold on plywood if it is well established. The best strategy is to encapsulate it. Apply two coats of shellac or oil based blocker/primer. Can you get under the porch? What do you see there?

  • Janice Janice on Aug 02, 2022

    You can treat the mold with borax and water and you;ll have time to do that before the install.. Here's a link for measurements. Personally, I'd check with the installer to see if they are going to use a good thick adhesive over the entire floor and ask them about the possibility of mold. It seems your first install many years ago was done very well! Good luck with your redo! :)

  • Vinegar may be a better option to kill mold. I would seal the floor before laying new carpet. An oil-based primer/paint would be my choice.

  • Figgy Figgy on Aug 02, 2022

    Yes, u need “wet and forget “ products

  • Mogie Mogie on Aug 02, 2022

    After treating the mold you need to do something so this won't happen again. Perhaps inserts for the windows so the rain can't get in during the wet months. This would also make this more of a 3 seasons type of room.

  • Cheryl A Cheryl A on Aug 02, 2022

    you need to get the mold taken care of first - and get estimates on what you can do to prevent mold from coming back if it rains - maybe tile would be a better option??

  • Deb K Deb K on Aug 02, 2022

    Hi Josefina, I would put a preservative on the plywood to prevent rot and mold, you can buy it at any lumber yard or home improvement store, it will also give you some piece of mind, we use this, and the smell does go away once it is fully dry for a few weeks

  • William William on Aug 02, 2022

    Might be a combination of dirt and mold. To be safe treat the floor with a 50/50 mix of vinegar and water. Bleach cleans the mold. Vinegar kills mold spores. Do not mix the two. Fumes are harmful. Prime the floor with Kilz or Zinseer primer to seal it.

  • Kathy Gunter Law Kathy Gunter Law on Aug 02, 2022

    I would paint with an exterior paint to help protect the plywood. That will be easier to repel water if rain blows in.

  • Dee Dee on Aug 02, 2022

    Vinegar is definitly the better option to kill mold, But it is not good for your health. Definitely get some shellack or since it is subject to the outside Marine Varnish and treat the subfloor before putting in more carpeting.

  • To kill mold, vinegar might be a better choice. I would apply floor sealant before installing new carpet. I'd go with an oil-based primer or paint. Or you can also paint it with an exterior paint. If rain blows in, it will be simpler to repel water from that.

  • Johnavallance82 Johnavallance82 on Aug 03, 2022

    Best to Seal the floor before having carpet laid.

  • Redcatcec Redcatcec on Aug 03, 2022

    The wood subfloor needs to be sealed before anything else is done. I would be curious to see if the sturdiness is compromised from seasons of contact with rain. You could take up a section of subfloor to see if the mold has penetrated through it.

  • Betsy Betsy on Aug 05, 2022

    Hi Josefinia: My suggestion would be to contact the folks who are going to put down the carpeting and ask them what they suggest. I don't know if they have a padding called Pet Padding. In my area that's what they call it. It's sort of an aluminum looking pad with rubber between the aluminum looking sheets and keeps the urine from going onto the wood beneath the carpet. I have it in my family room. What it does is to keep any liquid that gets on the rug from going through to the floor. You just use a wet vac to suck up any water that gets on the rug. If they have it, get it. It's just as soft, if not softer, as regular padding. I've had mine for over 15 years and it's great. If the wood is still wet, you may have to replace it, or at least parts of it. It might be a good idea to replace the icky parts and maybe put a marine varnish over the whole thing prior to carpeting. The part I think you're talking about just looks dirty, but it's not a really big area, so you might be able to replace just that piece.

    Good luck