Tech Talk: What Was the Most Unique Subfloor Prep Situation You’ve Encountered and How Did You Handle it?

Michael Dittmer
I received the typical “can you look at my floors because they are squeaking in a number of places?” call. I scheduled the appointment and investigated where the noises were coming from. According to the homeowner, the house was a relatively new home, built 24 years ago, and of good quality.

We walked around the main public areas on the first floor, which all contained wood floors. There were no obvious indications of a problem on the surface. When checking fastening devices, they were approximately the correct amount. From below, we removed the ceiling tiles and inspected the plywood to see if it was the correct thickness and to make sure the flooring was going in the correct direction. All things seemed in order on the first inspection.

A few years earlier, in the same neighborhood, we had a similar problem where the plywood itself delaminated due to a manufacturer’s defect; we rescrewed it from below and corrected that squeaky noise issue. Naturally, we thought that this would be the fix for this home. After rescrewing a few places we could not eliminate the squeaking/popping noises. While doing this, I noticed that the floor joists were loose in their hangers. Upon further inspection, I realized that none of the joists were shimmed tight to the plywood above, nor did the hangers have all of their screws and nails in place. We shimmed up two of the joists and placed screws and nails where they were missing. In these areas, the squeaks/popping noises disappeared immediately.

I took a few photographs and sent them to an architect for evaluation. The architect was in complete dismay because the nails that were used by the original builder were not the correct size or the correct amount, which could lead to very large structural deficiencies in the home. She recommended a structural engineer to assess the repair. I contacted a qualified licensed builder in the area to inspect those with me the following week. He knew exactly which screws and nails should be used with those specific joist hangers and manufactured I-joists to ensure a safe and quality installation. Within a month, he corrected all the deficiencies in the joist hangers and shimmed all of the joists up to meet the plywood to eliminate all the noises from the floor. We concluded that over the years the adhesive used to attach plywood to joists broke its bond and then the noises started to occur.

Jason Elquest
A unique subfloor issue was in a historic home in downtown Phoenix. The joist system in the house was old and in bad shape. It felt like you were walking on air when it was walked on; the whole floor moved. The original flooring was removed due to excessive damage from years of neglect. We added some additional joists and also added additional support to most of the existing joists. I say “most” because this customer had teenage daughters and he asked us if we could leave some squeaks in the hallway that led to their rooms, in hopes of hearing them if they ever tried to sneak out. My response was, “We can try.” It worked, and he was ecstatic. Only now that I have two daughters of my own can I truly appreciate the service we were able to provide.

Lenny Hall
A client had an older crawlspace house with the original diagonal 1x 6 subfloors, plus several previous additions both in T&G plywood subfloors over the crawlspace and in poured concrete, and the client was adding another one. It appeared that each addition was done without the rest of the house in mind.

Having various surface elevations and wanting no transitions for the new wood floor throughout, we used a laser survey grid to get elevations. We used the same idea as sleepers, but in the form of end-grain 2×4 slices that were cut ahead of time from 1/8″ to 1-1/2″, bagged by thickness and placed on the slab areas, plywood deck areas, and the diagonal subfloor areas according to the laser survey in an 8″x 8″ grid. The end-grain blocks became the support for the double plywood layer system to which the new wood floor was nailed. Moisture barrier materials were laid over the end-grain blocks under the plywood.

Scott Taylor
I was asked to determine why a solid wood floor was cupping in one area and not the whole floor. The general contractor hired several subcontractors to remodel a home in a suburb of a large city. The only way to determine the reason for the elevated moisture content just in that area was to remove the flooring.

During the interview process with the installing contractor, I was told that there was a dip in the subfloor, so he used a cementitious-based leveler to create a flat substrate. This flat substrate was the only way he would install the wood floor. After further investigation and removal of the flooring, it was discovered that the leveler should not have been used because there was no way to achieve the manufacturer’s nailing schedule (leveler would break apart if nailed into). The dry wood flooring ended up absorbing the moisture found in the leveler, resulting in the cupped floor.

3 thoughts

  1. I have cupping in my ne2 hard wood floor it is throughout the whole house, 2400 sq. ft. In an open floor plan it is very noticeable and was also very expensive. I did some research and realized it was cupping due to moisture somewhere. My contractor will not take responsibility for it in any way. I’m at my wits end as what to do. To have a renovated house with an open floor plan of 5 in white oak cupping all over is very upsetting. We let it sit for 18 months thru the seasons to see if it would settle down and it hasn’t. Please help me.

    1. Was the flooring acclimated properly? Did your contractor take moisture readings of flooring and sub floor? How was it installed? Glue and fasteners used together?

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