Flat versus level
A floor can be flat without being perfectly level, and for most floor coverings flatness is what matters. Manufacturers publish flatness tolerances, commonly expressed as a maximum deviation over a set distance. Floating LVP and laminate floors are especially sensitive: if the subfloor dips, the planks flex at the joints and can click, separate or wear out early.
Before installation we check the subfloor with a long straightedge and mark high and low areas, so the preparation plan is based on what the floor actually needs.
Common preparation work
Fixing squeaks and loose panels
Squeaks usually come from subfloor panels moving against joists or fasteners. With the old floor removed, loose areas can be re-fastened before the new floor covers them.
Grinding and patching
High spots on concrete can be ground down; seams and low areas on wood or concrete can be filled with a patching compound designed for the purpose.
Self-leveling underlayment
Larger dips may call for a pourable self-leveling underlayment. It needs proper priming, the right thickness and time to cure before flooring goes on top.
Replacing damaged subfloor
Water-damaged or delaminated panels, often near toilets, tubs, dishwashers and exterior doors, may need to be cut out and replaced. The full extent is sometimes only visible after the old floor is removed (flooring removal).
Moisture in Portland-area homes
Many homes in the Portland area sit over crawlspaces or concrete slabs and basements. Crawlspaces without an effective vapor barrier can push moisture up into wood subfloors, and concrete can release moisture for a long time. Too much moisture can cause wood floors to cup and can affect adhesives under resilient floors.
We check moisture in wood subfloors and look at concrete conditions before recommending a product or underlayment. If a crawlspace, drainage or plumbing problem needs attention first, we will tell you rather than covering it up.
How preparation shows up in your quote
Some preparation can be estimated from photos and measurements; some can only be confirmed once the existing floor is up. We describe the visible conditions in your preliminary quote and discuss any additional preparation with you before proceeding. Our installation cost guide explains how prep fits alongside material and installation.
Subfloor prep & leveling questions
Why does my new floor need subfloor prep?
Most floor coverings require a flat, solid, dry subfloor for warranty coverage and long-term performance. Preparation addresses squeaks, uneven areas and damage before they are covered.
Can you tell how much leveling is needed from photos?
Photos help start the conversation, but flatness is measured on site, and some issues only show once the old floor is removed. Any added preparation is discussed with you before work continues.
What is self-leveling underlayment?
A pourable cement-based product that flattens larger low areas. It needs primer, the correct thickness and cure time before flooring is installed.
Do concrete basement floors need moisture testing?
Concrete moisture should be checked before installing most flooring on a slab, especially wood products and glue-down floors. The flooring manufacturer specifies the acceptable range.