Leveling Uneven Subfloor


Hi There,

I hired a contractor to install Bruce hardwood floor 3/8″ thick. They were going to glue down the hardwood. They came & ripped up the carpet today & discovered that the sub-floor is very uneven, by about 1/2″ at certain point. Some area looks wavy. The subfloor is made of particle boards.

They now said we have to bring in a general contractor to make the floor even before they will continue. Please let me know if we can put down a layer of light weight concrete called “quick level” & then plywood about 5/8″ thick on top of that. This is on the second floor. There is another floor underneath this. We do not want regular concrete because it would be too heavy. Do you have any other recommendations that we can look into to make the subfloor more even?

Thanks so much in advance for your help.



Dear Mary

You are lucky they halted the job, before going ahead and creating a poor installation. I’ve heard too many horror stories about humpy subfloors. They would have blamed in on your house condition.

But to answer your question, no, you should not try the quick fix of pouring lightweight concrete on the particle board, it will be cracked up in no time. Simply hire a carpenter to remove all the particle board, sister the joists, if they are out of level, and install new 3/4″ plywood subfloor. Or upon removal of the particle board, you find another layer of old subfloor shim it level and install a thinner 1/2″ plywood. Either case it’s a floor carpentry job, that is out the expertise of these installers. You can then have a glued or nailed down hardwood floor installed.

I don’t know why your hardwood floor supplier did not tell you all this before you bought the wood. You may consider this all too expensive and may now want to return the wood, which should be an option.