Hi All,

First time poster here on this great site! We are looking to replace our carpeting with a 3/4" solid hardwood but the floor under the carpet consists of 3/4 particle board over 3/8" plywood. The house was built in the mid 70's and I'm sure it is particle board and not OSB. According to the sticky on "Particle Board or OSB" it says not to remove the particle board and nail 1/2" plywood over the particle board then place the hardwood.

That is going to raise the height of the floor too much, so is there anything wrong with removing the particle board (leaving the 3/8" plywood) and putting down another type of underlayment? The floor will definitely need some flattening as well. If so, what are my underlayment options, and installation method?

Thank's,
HD

I would always remove the particle board, then go back with 3/4" ply or OSB. Run it perpendicular to the existing plywood and make sure and stagger your joints.

I suggest you CAREFULLY re-read the sticky. It does NOT say not to remove the P. Board. It says, " IF the actual subfloor ( not underlayment over subflooring ) is particle board, THEN do not remove it. You have particle board UNDERLAYMENT, not subflooring. You are making a common mistake of misunderstanding underlayments and subfloors. Re-read the article carefully, making sure to understand everything it says.

If I read your post correctly, you think you have 3/4 inch particle board, OVER 3/8th plywood. I find this extremely unlikely. Did you mean the reverse?

in this area we see alot of 5/8" particle board over 1/2" ply. Pull the particle up and replace with 1/2" cdx plywood. I would also do what leaveling possible before the new ply goes down.

same here in NC with the particle board. I have laid over particle board several times, but I tell the homeowner that it is wrong and I can't/won't guarentee the long term. I recently had a customer tear up the particle board and had me nail the floor directly to the 1/2 ply subfloor. Once again I explained it was wrong but the customer made the final call.

I DO NOT condone these incorrect procedures but the customer is the boss. I can't turn down work even if they won't listen.

I never thought this was right either Dennis. One never sees that in my area. But I have learned this was a common practice at one in the Eastern US. It seems to be a false economy to me, unless labor was very cheap. Plus, the OP may mean 1/2" plywood instead of 3/8", which I have come to understand was a common building style in the Eastern US for a period of time.

Thanks for all the responses and clarifying the subfloor vs. underlayment issue in regards to the particle board. It will definitely be removed (particle board underlayment) prior to the new floor going in.

I'm not 100% positive the subfloor where we want to put the hardwood is 3/8", but I am sure about the particle board. I'm basing the 3/8" from the second story of the house. I'm remodeling the bathroom and had to cut up part of the subfloor due to water damage. It required 3/8" plywood to match the current height. As for the building practices, they also used 3/4" particle board in that bathroom to tile over. There is other 3/4" hardwood in the house and they used the 3/4" particle board to keep the carpeted areas near the same level as the hardwood.

Once we get into the project, I'll confirm the subfloor is 3/8", but based on the findings upstairs, I'm sure it is.

Thanks again,
HD

Most of the homes in western NC that are built like this are 1/2 ply with 5/8 particle. go back with either 5/8 ply or osb. Don't forget to mark/nail on joist

Thanks for the replies gentlemen. We finally decided on a floor, 3/4" Bella Cera Kempas and I'm going to do the carpet/underlayment removal and put down the new underlayment. We are doing a little over 500 sq. ft, including a small hallway, dining room, and living room/foyer. I've continued reading the forums for additional information and tips, but still have a couple of questions on preparing the sub floor (yes it is 3/8" plywood). I want to do this right, but I also don't want to over engineer either.

1) Plan is to use 1/2" ply as the new underlayment. Is 5/8" plywood needed, as I'm trying to keep the height under control as a few of the other rooms which the new hardwood is going to meet up with original hardwood to the house. The old hardwood is 3/4" x 2 1/4" hardwood nailed to the 3/8" plywood sub floor.

2) BCX, CDX or OSB? From reading many of the posts, and even the sticky, OSB seems to be the least preferred. So BC or CD?

3) The current 3/8" plywood sub floor is perpendicular to the 2x10" joists (as it is supposed to be), should the new 1/2" ply be perpendicular but offset (thinking I rip some sheets so they are offset by 2') or parallel to the joists?

4) With the square footage of underlayment, I'm not opposed to getting an air nailer (who can refuse a new tool), so what size nail (or staple) should I use?

5) Do I add a bead of glue as well to the plywood before nailing or stapling down?

Thanks again for all your help!
HD

With the help of my father in law and brother in law we pulled up 511 sq ft of 3/4" particle board. They were a great help, it would have taken me a week to do it alone. The subfloor is pretty crappy, 3/8" plywood, that is glued to the joists, and only stapled! It was scary walking on that 3/8" plywood, kept my feet on the joists, heard some scary popping sounds if I stepped on a seam (no blocking).

I wrote the APA and they referred me to their technical bulletins. My plans are to go over the floor with 1/2" BCX (may go with CDX) plywood. Their specifications call for 3d x 1 1/4" ring shank nails 12 1/2 gage shank dia. to go in every 6" on the panel edges, and 8 each way for the intermediate. Will stagger the joints of the new 1/2 ply vs. the 3/8 that is in there and I'm thinking screwing and gluing instead of the nails.

Any thoughts or suggestions? Plywood gets picked up tomorrow!

Personally, I think adding 1/2 inch ply over 3/8th ply should be sufficient. But, definitely you should offset all the joints, and add glue to the mix. Either using a PL type or preferably (my thought) full trowel adhesive designed for parquet applications.