concretemoistureslab
Should I be concerned about moisture with installing an Engineered Wood flooring over a concrete slab (on-grade)? We have been living in the house for 10+ years with carpet flooring and I don’t recall the carpet ever being moist (except for spills of course). However the room does feel a bit humid on a rainy Summer day. Should I be concerned about moisture affecting my installation?
This is the product I am considering installing: SolidPlus® engineered Flooring by Somerset Floors
There are 3 potential moisture issues:
You need to first figure out which of those 3 is happening.
If the water is leaking in, that's an issue of gutters, grading, draining, etc. That needs to be fixed on the outside, first.
If moisture is migrating through the slab, then you may have a high water table. If that's the case, I wouldn't bother finishing the basement. If it's just a bit of moisture, you could get by with putting down plastic underneath the laminate flooring.
If it's high humidity, then this might be the gap issue. Engineered floors shouldn't expand/contract as much as real wood, but they still need plenty of space around the edge of the room to expand. Check for that. Otherwise, get yourself a quality dehumidifier and have it run 24/7.
From a comfort and water protection perspective, I think you'll find it beneficial to install a sub floor. I'd recommend one which allows for ventilation beneath it such as these 2x2 panels you can buy at Home Depot/Lowes
This will give you a nice, warm "softer" surface to put your carpet pad on, and help protect from any condensation issues with the cold floor beneath by allowing it a place to form, and then with the proper ventilation openings cut into the subfloor (standard floor vent in the carpet to allow airflow) it'll dry out on its own.
Best Answer
You have to put something between the concrete and the engineered flooring. Whether this is a thermal barrier or plywood depends on what type of engineered flooring you put in and how much moisture the floor has.
All concrete floors have moisture. This might be next to nothing or a considerable amount, even in an unnoticeable way. To make matters worse the engineered flooring you are getting might be pretty closed system or rather breathable it is really hard to tell. Also with an on-grade install the moisture levels of the concrete can vary by season or year. Heavy rains for a month might cause a slight issue after 5 years of no moisture at all.
I have two pieces of advice:
If putting engineered on an on-grade slab make sure the backing of the flooring is a real wood - in a hard plywood form. No mdf/mush/particle-board type of back - period. They will warp on you. I mention this because most stuff that is a decent price at most local stores will be made out of crap backing (don't care if it has padding or not). These products are only for the simplest of installs - on commercial type concrete or in a residential above grade. An easy test is take samples and put them in a bucket of water for a few hours, let them dry and see how they look. The other option is getting pure vinyl click lock which is getting pretty damn close to engineered in the way it looks. You have to look pretty close to tell its not a wood product for the good ones - which can also mimic tile.
Follow the manufacturers instructions - call them if you need to. Not the store's instructions, the manufacturer's. If they tell you, you can install it directly on the floor but they suggest a 1/2" plywood - do the plywood. I personally haven't heard of many manufacturers of engineered flooring that will OK direct concrete install that is on-grade but who knows. Got to hit their website and call them. 20 mins of research can save you time and headache.