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Need Help Regarding Hardwood Flooring and Subfloors


jgw517's Avatar
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07-27-13, 10:27 AM   #1  
Need Help Regarding Hardwood Flooring and Subfloors


I am having hardwood (3/4") floors installed in about a week and I have concerns that are causing me to loose sleep. Right now I have 3/4" hardwood in Living Room - Carpet is down hall and 3 bedrooms (this is where I am having hardwood put down).

My specs on this house (built 1999) say I have 2" x 10" floor joist with 2 layers of subfloors: 1/2" sheet exterior fir plywood plus with 5/8" particle board on top of that.

Here is my problem. I know they have to take up the particle board, carpet and pad in the hall and 3 BR. That leaves the 1/2" fir plywood subfloor. Is that going to be enough for the 3/4" hardwood that I am having installed?

I have done the math and I am pretty sure my LR hardwood must have been put down on the 1/2 subfloor alone because total LR is 1-1/4" total height (1/2" sub plus 3/4" hardwood.

Hall and 3 BR measure the 1/2 sub + 5/8" particle sub, plus 1/2" carpet pad plus carpet which measures approx. 7/16" for a total of approx. 1-1/2".

This is about 1/4" difference in height and that is about how much more taller the hall carpet is compared to LR hardwood.

Everyone I have talked to tells me that 1/2" subfloor is not thick enough but if I add more then the difference between LR and Hall would be very noticeable when both are hardwood.

Is the 1/2 subfloor going to be enough. I have even been told I will not be under code this way.

Another note: The mfg. of the floor I have purchased list 5/8" as min. subfloor. I am only 1/8" off and wonder if this is going to be ok?

Thanks to anyone who can help me out with this.

 
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chandler's Avatar
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07-27-13, 03:21 PM   #2  
Welcome to the forums. A transition from the living room to the hallway is far superior to having a weak floor. Are you dead sure the first subfloor is only 1/2"? It is odd not to have 3/4" subflooring topped with thinner stuff, but bottom line you need 3/4" subflooring for a substantial install.

 
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07-28-13, 05:40 AM   #3  
Thanks Chandler
I have no way of knowing exactly how much subfloor is in the living room but doing the math it appears to be 1/2 as was stated in my specs for the house. After carpet and particle board subfloor are removed I don't see how I can add additional subfloor without it ending up higher than the LR floor is now. The store where I purchased my new hardwood said the 1/2" subfloor would work with the floor being laid to run opposite direction than joists. They also said 2x10 joists would offer better support. Being a woman I am trying to learn. Unfortunately I listened to them and paid 1/2 down. I was told that the worst that could happen is that if it creaked or gave I could have it braced from under the house. Of course I don't want to have to do that. The only way the subfloor in LR could be thicker is if it sits lower than other subfloor. Not knowing construction I don't know if this is possible. The mfg. of floor said 5/8" minimum subfloor and I am 1/8" off from that so I guess I have to hope for the best. I might also add that my LR floor is very strong and in 14 years I have never had so much as a creak from it.

 
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07-28-13, 05:50 AM   #4  
Remove one of your floor registers to get a look at the subfloor. You should be able to determine how thick the sub floor is by looking at the edge. IMO. the 1/2" would be ok where the hardwood can be nailed to the joists but the shorter pieces where they are only nailed to the plywood might not have enough. The floor can be reinforced from below but it will cost more - especially if you are paying for labor!

They also said 2x10 joists would offer better support.
What size joists do you currently have? how long is the span between supports of the joist?


retired painter/contractor avid DIYer

 
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07-28-13, 05:54 AM   #5  
If you move forward with an installation that does not meet minimum manufacture recommendations you void any and all warranties as well as release from any liabilities the installation company who will put the floor down. You will be the only one with skin in the game, everyone else gets a paycheck without care.

If you are having the particleboard removed anyway, I would recommend that you also take up the 1/2 inch and replace with a quality 3/4" T&G subfloor such as Advantech (screwed and glued). Floor heights and transitions should not be the guiding factors in how this floor is installed. I would also be concerned that the installation company does not have a problem with the inferior install. It comes down to flex/excessive movement between the joist due to insufficient subfloor AND a subfloor that is too thin to provide adequate grip for the fasteners used to nail the floor down. Both may result in a noisy floor install.

 
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07-28-13, 08:12 AM   #6  
I did remove the register but all you can see is that the hardwood floor is 3/4". I tried pulling up a corner of carpet in hall where it meets the subfloor and the LR hardwood is approx. 1/16 above the particle board subfloor that is in the hall. Specs say "joist are 2 x10 where most homes are 2x8". It appears that the particle board subfloor runs under the baseboard which my understanding is it will have to be sawed and cut to remove. Unfortunately being a widow I don't have the capability of doing this to see further under the particle board. I wish I could attach a copy of the flooring plans for you to see but don't see that capability here. It looks like 6' between each of those posts in the ground (not sure what they are called). Thanks so much for your help.

 
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07-28-13, 11:49 AM   #7  
OK my thanks to everyone for all the help. I removed the threshold and pulled up the carpet in Hall next to LR hardwood floor. I chiseled away enough particleboard and the LR hardwood flooring is only on 1/2" of plywood like I originally thought. But the shocker was that there is only 1" particleboard subfloor under the carpet in my hall. There was no 1/2" plywood like specs said. I put a yardstick in and it went all the way down and would have disappeared had I dropped it. I went back to my specs from the builder and even though it says "2 subfloors - 1/2" fir exterior plywood plus and 5/8" particleboard" down at the bottom of the sheet in very small print it said "Information Deemed Reliable but Not Guaranteed". Lesson Learned!! I will not have a new subfloor put in. Thanks to all.

 
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07-30-13, 02:15 PM   #8  
Particleboard Subfloor

Now I need additional advice. I have purchased hardwood flooring then found out that I did not have the 1/2" under 5/8" particleboard like my specs to house said. I only have a 1" particleboard subfloor. I know that has to come out. My question: is it safe to cut the particleboard out around the wall area and then put down plywood for a subfloor.

I have read that when you do this you are weakening the foundation for the interior walls. I have also read that it is ok to do it this way. Can anyone give me advice before I proceed. It would be greatly appreciated.

 
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07-30-13, 02:49 PM   #9  
If you pull the baseboard, you most likely will find that the particle board only goes up to the edge of the stud wall and not under it. Either way, it needs to come up. I would not worry about the exterior wall or foundation and it is OK to cut up to the bottom plate to replace.

 
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