It may not look like the case, but often you might pull away your old carpet to discover the floor is uneven and bumpy. So why is this a problem? You cannot install a hard floor over an uneven subfloor. Doing so could result in creaking noises and movements between the boards.
Depending on the situation, you can either sand down areas of the subfloor that are too high, or install shims beneath the subfloor so that the entire floor is brought up to the same level.
Subfloor unevenness cannot be greater than 3/16 of an inch over a 10-foot span or 1/8 inch over a 6-foot span. Subfloors must not slope more than ½ inch per 6 feet (25 mm per 1.8 m) Subfloors must be structurally sound. When making a concrete substrate level, use a portland cement or gypsum-based floor patch.
Uneven subfloors are a common issue. I have heard from installers that some homeowners do not want to pay for getting the subfloor to within flatness tolerances, which can get expensive so they continue the job without taking this critical step.
If the subfloor is uneven, with dips, ripples, or waves, this irregularity will be telescoped through to the surface floor covering and can even cause the flooring installation to fail. For example, ceramic tile installed over a bad subfloor can result in cracking grout or broken tiles.
In some cases, a slight slope may be normal and not cause for concern. However, if the slope is severe or getting worse over time, it could be a sign of a serious problem that requires immediate attention. One potential risk of sloping floors is damage to the structural integrity of the home.
When a subfloor starts to creak and the nearby floors are uneven, sunken, or sagging, it's likely time for a replacement. Repairing a damaged subfloor has a typical price range of $300 to $2,500.
Uneven floors in a house are usually a sign of a foundation problem, but not always.
If you have an uneven sub surface, a underlay floor can potentially help level it out, but we don't recommend this at all.
Hazardous Uneven Floors
If a floor is uneven or has some type of inconsistency, people in the vicinity of that floor are put at risk for tripping, stumbling or falling down. When a floor is hazardously uneven, it's up to the property owner to fix and adequately maintain that floor.
Most flooring manufacturers recommend a variation of no more than 3/16 inch over a 10-foot span. Floor leveling is a relatively easy DIY project, although some subfloors with rot, insect damage, or structural issues may require professional attention.
Check the Level of the Subfloor
To check for small high or low spots that may not even be visible, place a long level or straight pipe on the subfloor. Move it around to different areas and mark any high or low spots you find with a pencil or marker. Most floors will have at least some slight variations.
Forgetting to level the subfloor
The subfloor must be level before installing laminate flooring. If the subfloor is leveled, the laminate planks will not lay properly, causing uneven and unsightly floors. If the subfloor is not level, you can use a self-leveling compound to level it out.
The best flooring for uneven floors due to its attractiveness and durability is epoxy, which can also be designed to mimic a wide variety of appearances. Not only will epoxy finish out the floor, but it'll also even it out.
The easiest way is to use a self-leveling compound, also called liquid floor underlayment or floor resurfacer, within sections of level-cut rails. The material flows out like thick syrup, then hardens into a smooth, perfectly level surface, sometimes in less than an hour.
To avoid buckling, subfloor panels should be spaced with a 1/8-inch gap at all edges and ends to provide room for naturally occurring expansion. Tongue-and-groove edges on many premium floor panels, such as Weyerhaeuser's Edge Gold® OSB panels, are designed to self-gap.
For homes where this is the case, the subfloors likely need to be replaced. According to Angi and HomeAdvisor, the cost to replace a subfloor ranges from $428 to $2,978, with a national average of $572.
As mentioned above, it's common to find slanted floors in a house more than 15 years old due to the home's foundation shifting over time. However, the uneven floor may be an indicator of a larger, unseen problem with the house.
The first step in fixing uneven floors caused by foundation issues is to address the foundation problem itself. This may involve adding additional support to the foundation or repairing any damage that has occurred. Once the foundation is stabilized, you may need to have the floors leveled by a professional.
In general, homeowners insurance covers subfloor water damage. However, it must be caused by one of the perils listed in your insurance policy. If you have an HO-2 policy, your building, including the floor, is protected against various threats, such as a ruptured water heater or pipe.
Uneven floors are most common in old homes because the home's foundation shifts over time. For example, it may take about 15-20 years for a foundation to shift and the floors to become uneven.
Replacing a subfloor can sometimes escalate into a bigger project, but there are some cases where you can remove parts of the subfloor without having to take down the wall.
In layman's terms, this means typical 2-by-10 floor joists, spanning 16 feet, can be expected to sag about one-eighth to one-quarter of an inch. Not much; however, as the span increases, so does the amount of deflection. In any case, the floor system can be repaired.