Installing Wood Floors with Uneven Subfloors: Wood & Concrete

Before installing wood floors you may be spending a lot of time picking out the perfect hardwood flooring for your home and imagining how much its attractive warmth should improve the room. There are other issues though that may need a little attention before getting too far along.



Carpeting and a thick pad can hide a lot of problems with your subfloor – issues that can affect the feel and appearance of that new hardwood floor. In most cases your new flooring will be installed over a wood or concrete subfloor and each type may have potential problem issues that should be addressed.


Installing Wood Floors over a Wood Subfloor

A few of the issues you may encounter when installing laminate, engineered, or solid hardwood flooring over a plywood or particle board subfloor:

• Sloped floor – if you live in an older home with sloping floors, there isn’t much of a cure short of doing some major structural work. Fortunately, sloping in an older home is often considered to add character to a floor, so installing on the subfloor should be okay.

• Sagging floor – a floor that sags in just one area may have a cracked or broken framing member under the subfloor. Removing plywood where needed and scabbing new framing to the sides of the damaged piece at the correct height can often cure the problem. Reinstall the plywood and you’re ready for your wood flooring to go down.

• Loose flooring – subfloor that has become loose over the years can often be refastened with screws or nails. If it feels like you’re not hitting anything solid, you may need to remove the section of plywood and scab additional framing to the existing joist.

• De-laminated floors – plywood that has gotten wet during construction or while in the home can have soft spots where the layers have delaminated. These sections should be cut out and replaced regardless of what type of wood flooring is being installed.

These are the major issues you may encounter when installing wood flooring over a wood subfloor. If any subfloor boards appear to be uneven at the edges, they can often be lined up with additional screws.


Installing Wood Floors over a Concrete Subfloor

Solid hardwood floors can’t be installed over concrete so these tips only refer to placing engineered or laminate flooring down over a concrete subfloor. Unfortunately both of these products are a little thinner than solid flooring so any problems with the subfloor are a little more evident if they aren’t corrected prior to installation.

Read on and check out the video about concrete subfloors below!

The two primary issues when dealing with concrete:

• Floor humps – high spots in a concrete slab can normally be felt as you walk across the room and should be ground down before your wood flooring is installed. This job requires a concrete grinder and can create an extreme amount of dust.

If you’re grinding in a finished room, try to cover everything you possibly can and if you anticipate installing wood flooring in a room you’re remodeling, do your grinding before any painting is done – you’ll be very glad you did.

• Low spots – it’s not unusual for a concrete slab to have low spots and once again, they can normally be felt when walking across a room. Using a string line across the slab and measuring down can also indicate possible trouble areas. Home improvement and flooring stores usually sell concrete patch that can be used to float the areas up even with the rest of the slab.

If you’re not used to working with concrete, it may be a good idea to call in an expert to correct any problem areas in your concrete subfloor before starting the wood flooring installation.


Check out this video on preparing concrete subfloors including tips for installing wood floors:





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