Subfloor Repair, Leveling and Moisture

Q: Does my subfloor need to be leveled before a new floor?

It needs to be flat more than level. Dips and humps show up later as hollow sounds, gaps or boards that move. The installer checks with a straightedge and corrects what is outside the tolerance for the floor being installed.

Q: Will leveling raise my floor?

Slightly, where compound is poured. It matters at doorways, stairs and where the new floor meets another one, so those heights are checked before the pour.

Q: How do I know if moisture damaged my floor?

Look for boards with raised edges, dark stains, soft spots or a musty smell. A contractor confirms it with a moisture meter. One La Cumbre customer wrote that Tony pointed out small details that other floor contractors failed to recognize.

A new floor is only as flat and dry as what it sits on. Before installing, La Cumbre checks the subfloor with a long level, replaces damaged plywood, takes off old adhesive and pours leveling compound over the low spots in a slab. Google reviewers describe leveled concrete slabs, moisture damage, and foundation issues handled inside the original timeline and budget. Photos of each step are on this page.

How the floor gets checked

Flat comes second. Dry comes first. In Tony’s words:

“We test both the wood and the subfloor using calibrated pin and pinless moisture meters, and we perform ASTM moisture tests before any installation.”Tony

A long level or straightedge is laid across the floor in several directions. Any gap under it is a low spot, and any rocking is a high one. The usual limit for nailed wood floors is 3/16 inch in 6 feet or 1/4 inch in 10 feet. It is explained in the new floors guide.

A crew member kneels and holds a six-foot level over a low spot marked on a slab — A long level over the slab finds the low spots. They get marked and filled.

A bare subfloor beside an iron stair rail, with a patch of metal mesh and a long straightedge on the ground — Old floor out. The subfloor gets checked with a straightedge before anything goes on top.

Wood subfloors

Soft, stained or broken plywood is cut out back to the joists and replaced. Old glue left from a previous floor is taken off so the new adhesive bonds to wood and not to residue.

A floor opened down to the joists, with spray foam between them, plywood pieces, tools and a long level laid across — Opened to the joists. New plywood goes down and the level tells us when it is flat.

Two crew members with a floor machine and vacuum hose take old black adhesive off a plywood subfloor — Old adhesive ground off the plywood, with the vacuum running the whole time.

Concrete slabs

Low areas in a slab are filled with leveling compound, which is poured as a liquid, finds its own level and hardens. High spots are ground down.

Wet gray leveling compound spreads across a room around a patch of old slab, with an empty bucket in the middle — Leveling compound poured across the room. It flows flat and sets hard.

“Toni and his crew are absolutely amazing!! They leveled the concrete slabs, installed cork underlayment, and the LVP beautifully in < 4 days. They were in and out, extremely professional, and kept everything clean. The crew even took out all the vinyl planks and put all of the same planks in piles to ensure none of the same looking planks were next to each other when laid down. 10/10.”Kristin H. · Google review

Moisture damage

Wet wood swells, cups and eventually rots. The source of the water has to be found and stopped before any boards are replaced. What cupping and buckling mean is in the repair guide.

“TONY, and his crew were great. Always on time and kept us updated on their every progress. We had moisture damaged to our dining area and hallway. He pointed out small details that other floor contractors failed to recognize. Luis and his crew replaced our dining and hallway area, sand and finished the rest of the house to match, the result was amazing. I highly Recommend LA CUMBRE FLOORS. They don't have the lowest prices, but the result is worth it. I was amazed by everything they were able to achieve, thanks to their experience restoring very old and deteriorated floors.”Héctor D. · Google review

When the house has bigger problems

Sometimes the floor is the first place a foundation or framing problem shows. A flooring contractor can point it out and work around it, and will tell you when it needs another trade.

“Tony was wonderful to work with. Incredibly knowledgeable about flooring, sub surfaces and foundation issues and walked us through a few different options we could take along with the long term effects of each option. Ultimately, we chose flooring that would be durable and work with our house overtime, and Tony and his team executed the project beautifully and even remained in the proposed timeline and budget amidst issues found with our foundation. I highly recommend!”Brittany A. · Google review

Concrete, cleaned and coated

A clean, sound slab can also be the finished floor. See epoxy garage floors and polished concrete.

Two crew members in La Cumbre shirts kneel at the edge of a wet coating spread on a concrete floor — A coating going down on concrete.

A crew member vacuums a concrete floor in a commercial space, part of it already shining — A commercial concrete floor, cleaned and vacuumed, part of it already shining.

Gray leveling compound poured partway across a room with a stone fireplace — Leveling compound, partway across a living room.

Questions

Does my subfloor need to be leveled before a new floor?

It needs to be flat more than level. Dips and humps show up later as hollow sounds, gaps or boards that move. The installer checks with a straightedge and corrects what is outside the tolerance for the floor being installed.

Will leveling raise my floor?

Slightly, where compound is poured. It matters at doorways, stairs and where the new floor meets another one, so those heights are checked before the pour.

How do I know if moisture damaged my floor?