Hello everyone, very nice message board here. Over a year ago, my wife and I bought a 6 year old, two story house in Round Rock, TX. There is currently some really cheap carpet that will need to be replaced in the upstairs (and some downstairs). We are looking into replacing the carpet in our upstairs bedrooms (3 of them) and large gameroom with a hardwood. It is a total of about 800-900 sq. feet to be replaced.

The upstairs in my house has an OSB subfloor. I haven't yet been able to determine its thickness as there are no floor vents. Does anyone have a recommendation to determine the thickness besides cutting out a chunk? The downstairs is a slab with no basement so the downstairs doesn't offer any help. Anyways, the subfloor looks like it was just nailed down and will need a bit of work to level in some areas.

The other thing i was looking for advice on was floor type. If we do wood, I would want it to be a solid (possibly engineering) for long lasting and improving re-sale value. I think a 3/4'' would work, but probably not if I had to add a plywood underlayment. I think it would create too much of a thickness change between the rooms and the adjacent foyer/stairs (which we were planning on keeping as carpet.

The final thing that will make the decision is cost. It is well within our budget if we can do this as a DIY or with some consulting help. I think I will be capable doing the layout and nailing, with some practice but it sounds like the most critical/difficult part is the subfloor prep. It looks like Perry is our regional expert on that. I was wondering what his thoughts on that were.

Any thoughts/opinions on this are welcome. Thanks in advance.

Hello neighbor!


The OSB used for subflooring around here is usually T&G 33/32.

I would screw all the OSB down really good, and pull any nails that can be found. The nails will eventually squeak.

Without buying a special aluminum screed yet, get a long straight 1x6 and check the flatness of both the upstairs OSB for peaks at the panel edges and valleys between, also to check the downstairs concrete.

These areas need to be addressed. The flatter you get the subfloor the more pleased your going to be about the final product.


A solid wood over concrete is risky and more costly then an engineered, as a trowel or rolled on moisture barrier will positivly be needed, instead of maybe. Concrete moisture vapor emissions testing is recommended and required by all wood manufacturers.

Prep is by far the hardest, and most important part of the whole job. Many don't understand that and to save time and initial cost, fail to do it, or enough of it, when an effort is actually made to correct it. Then hindsight is always 20/20, when things start to go wrong.

Because of the always "unknown" floor prep it is impossible to put a firm number on the cost of floor prep, unless a contractor likes to loose money, or on the other hand, feel like they ripped off the client because after all, it wasn't much floor prep as thought. To be fair to my clients and me, I bill consulting and floor prep by the hour + any materials I supplied.

I don't know if I have posted any pictures here, of what it takes to do proper floor prep. I have a lot of them stored on my computer, waiting to load on my website, if I ever get it done.

Get it done! It's about time some of you guys have websites. You're in the 21st century afterall

Thanks for the feedback Floorguy! At this point, i think we are only going to work on the upstairs. I am primarily interested in improving the bedrooms (especially the master) and my game room.

Is it safe to assume that a 33/32 OSB that I will not need to add an underlayment or does it really depend on how level and firm the OSB is? The problem is I don't want to order a 3/4'' solid or engineered for the upstairs and then find out I need another 1/2'' in plywood.

I will go get a long 1x6 to see how level the subfloor is. I know in some spots it will need some help, but maybe the screws will do the trick. I was going to get my carpet stretched soon and hoped to screw down much of it then.

Any pictures that can be posted on how to address dips would be greatly appreciated. I have seen others mention using shingles to make up the thickness difference but am having a hard time visualizing it.

For a nailed or staple down install, is the general concensus that a solid hardwood is best? It seems the engineered floors have quite a few benefits. Is the only drawback of engineered that it can't be refinished many times?

I have heard tell that a fella can drill a very small hole down through the plywood and insert a dental tool or dental pick to determine the thickness of the subfloor.

Best to try that in a closet.

Well i don't know about getting a dentists to come out to your house to look at your subfloor. I had one pull a tooth one time cost me arm/leg and i went to his office. don't think i could afforded him to come to the house. I screw it down real good/check level float low plane high spots. Think about a engineered floor lots to choose from wood on wood is good glued down. No hieght problems downstairs. I go with Floorguys recommending a moisture barrier. I'll wondering what kind of roll on he likes myself? Jerry T don't get your jam saw cought in the corner i was just kidding about the dentist. New to the neighbourhood yull have to forgive me. GOOD LUCK WITH YOUR FLOOR!

Uhhhhh..., if you are gonna cover the floor with wood, why not just take a 3/4 in paddle bit and make a hole in the floor? That way you could just stick a tape measure in the hole.

Thanks for the feedback. I have a narrower width tape measure. I think I will go with a little smaller bit and drill a hole in a closet.

Ok, I followed everyones advice. Thank you. Here is what I have. I have 3/4'' T&G OSB with 24'' spaces between joists o.c. I understand this is below the minimum recommended spacing (over 19.2'').

I am wondering what your opinion on what I should do is? I would like to install a solid, but is adding a 1/2'' or less CDX plywood underlayment enough to strengthen the floor? If I added a full 1/2'' underlayment, I would have to go with a thinner solid to not add too much thickness. Do "y'all" think I will have good success with an underlayment and thinner solid or do you think I should scrap my desire for wood? I don't want to invest all the time and money for wood if the results are going to be poor. What do you recommend?

Install the 1/2" plywood underlayment and flaten the subfloor. You could install a solid over that quite easily. BR-111 has 5/16" solids that look good and could be glued down over the plywood. Bruce has Natural Reflections that is a 5/16" solid and is quite reasonable in cost and can be stapled as well as glued. Of course many 3/8" engineered as well. Had your subfloor been laid 16" oc over the joists no plywood would have been needed for a 3/4" solid. As it is, I'll bet there are low places between each joist as the OSB sags.

Thanks Gary. You mentioned gluing the BR-111. That is the brand I have been looking most at. Do you know of issues stapling the 5/16'' solid?? I feel more confident stapling than gluing myself.

The last thing is the moisture measurements. What type of moisture meter do you recommend?

You can staple it with the LHF gun or a crown stapler.

ok, I found something a little weird. I was verifying the joist spacing in my 20x19 game room. In this room, the joist spacing is 16'' o.c. In my bedrooms mentioned before, the joist spacing is 24'' o.c. I have 3/4'' OSB as my subfloor. I was already planning on installing a 1/2'' underlayment with a 7/16'' solid in the bedroom. Should I skip the underlayment in the game room and go with a thicker solid? Or do you think I should go for the underlayment and thinner solid just to keep it consistent with the bedroom? I was going to do the game room and bedrooms in seperate orders so keeping everything in the same batch of material isn't a concern.

I would cover it all with plywood, and order all the materials.to cover it all so it doesn't look blotchy as you transition.

Thanks for the feedback. My gameroom is located above my garage. I haven't tested the moisture content of the subfloor yet, but my guess is this will be a higher risk than the other rooms. The garage has a "finished" ceiling (cannot see the joists), but I bet this floor will see greater swings in temp. and humidity based on the outdoor conditions. i think the additional plywood underlayment and the additional moisture barrier will help. Based on everyones experience, is anything else to watch out for or do to mitigate this issue. Once i get a moisture meter it will be interesting to see how the floor changes when we get a swing in weather. Lately it has been very dry here in Austin, so I would be a bit worried that swings in weather could play a role. What do you guys think?