# Dip in subfloor



## Casey (Aug 9, 2005)

As I am getting ready to install (nail) 3/4" hardwood floor planks I notice I have an area in the plywood subflooring that is uneven. It is located in a high-traffic area where heavy furniture was. The section is also where two pieces of plywood are joined and are not quite level. There is also a section of the plywood which dips where the surface wood was pulled out. 

What is the best action to take to ensure the subfloor is level? Can I 'fill in' the uneven areas with roof felt? Any advice is will be greatly appreciated. I am deep into this project and have come to a griding halt.

Thanks,
Casey


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## jproffer (Mar 12, 2005)

You're not going to like my answer....I warned ya...here goes:

To fix it right you need to pull up the plywood around the area and see what is really causing it to sag. The joists are either: A) rotten B) settled or C) sagging themselves. If they're rotton, replace them (obviously), if they're settled, jack them up and support them, and if they're sagging, support them from underneath and sister on more lumber (with the crown up). In either case, replace old plywood with new, and you're ready to floor.

"Filling in" with roofing felt isn't really a viable option. It may work (I doubt it, but it may), but it's not the right way to acheive a long lasting repair. Better to fix it right now, than to fix it right later after you pull up all your new hardwood flooring.


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## JustaFramer (Jun 17, 2005)

jproffer said:


> "Filling in" with roofing felt isn't really a viable option. It may work (I doubt it, but it may), but it's not the right way to acheive a long lasting repair. Better to fix it right now, than to fix it right later after you pull up all your new hardwood flooring.


Well said.

However I don't think you have to pull up the plywood unless there is cracking from stress. Plywood can take some deflection without damage to the material.
Look for the problem from the crawspace/basement or from underneath.


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## Casey (Aug 9, 2005)

*Leveling Mortar on subfloor*

Thanks for the responses. The bow in the subfloor is about 1/4" at the lowest spot. Will leveling mortar work? The house is 20 years old. There are other sections that are uneven where the plywood seems are off approximately 1/8th of an inch. Do I need to try to level these seams out as well? Any advice you can give is greatly appreciated.

Casey


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## JustaFramer (Jun 17, 2005)

Sounds like a crown in the joist or a sagging joist. Leveling mortar will work great. Don't use water to mix with it. For a near crack proof bond use what I can't remeber the name but is a latex based solution.
You could also try planing the high areas dows a little bit but not much.


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## jproffer (Mar 12, 2005)

Keraply...Admix...ummmmmmmm...if not those 2, I dunno.


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## Casey (Aug 9, 2005)

Ok, here is an update. In reading the tiny, tiny print on the instructions and talking with the manufacturing company, they say use roof felt to fill in the bow(s) as needed. They state do not use the leveling mortar. Just thought you might like to know. Thanks again.


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## jproffer (Mar 12, 2005)

, well good luck to you.


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