Q: My husband and I recently purchased an older home and are remodeling. We pulled up the old carpet in the family room and discovered that a little more than half the room has the original raised, wood subfloor while the rest is a cement slab from an expansion/addition the former owners had constructed. We would like to put down real hardwood or engineered hardwood but are unsure of how to prepare the subfloor. Where the two material meet they are a bit uneven. We were considering a self-leveling compound but we fear that the wood will flex and the cement won’t resulting in cracking and an uneven floor. We’ve also considered covering the whole floor with thin plywood or a similar material. What would you suggest for leveling a floor with two completely different types of subfloors? Thanks!
Kristin
A: Depending on which area of your subfloor is lower, will determine what method is best to do. Let’s look into a few options:
First of all, I would not suggest putting plywood over the concrete. To do this you must glue it in place and unless you have done this several times, it’s a pain to do and has a higher rate of failure than other options.
If the concrete portion of the subfloor is lower, than using a leveling compound is a good bet. If you have worries about it cracking because of the wood expanding more than the concrete (which does expand and contract some) make sure you use a latex additive to give the leveling compound some elasticity. Another option would be to build a slow, sloping ramp, but it’s a bit less work and more reliable to simply bring the entire concrete portion level.
If the wood subfloor is lower, than using some plywood nailed in place to shim up the floor is a good bet. Follow-up with a bit of leveling compound to make sure that the concrete floor is level as well and you should be all set for installation. Remember, you want your subfloor to be flat and dry. If there is a sizeable gap between the wood and concrete portions of the subfloor, fill it like you would repair a crack in your concrete.
For the flooring itself, you will want to use an engineered or 5/16″ solid hardwood floor which is approved for a glue-down installation. You could also do a floating hardwood, but you must have a moisture barrier in place over the entire floor. In the case of glue-down, the adhesive will act as your moisture barrier. Before installation, give the flooring plenty of time to acclimate and ensure to moisture test before installing. Try to make sure the flooring and subfloor’s moisture content is within 4% of each other, and try for 2% if doing glue down.
