How to Prepare Your Subfloor for New Kitchen Flooring
The most beautiful flooring in the world will fail if installed over a bad subfloor. Squeaks, cracks, uneven tiles, and premature wear all trace back to poor subfloor prep. This step is unglamorous but absolutely critical—it's the foundation that determines whether your new floor lasts 5 years or 25 years.
Quick Summary
Time needed
4-8 hours
Cost
$100-300
Difficulty
Moderate
Why Subfloor Prep Can't Be Skipped
You might be tempted to skip this step, especially if your old floor looked fine. Don't. Here's what happens when you install new flooring over a poorly prepared subfloor:
With Tile or Stone
- • Cracked tiles within months
- • Lippage (uneven tile edges)
- • Grout cracks and falls out
- • Hollow-sounding tiles
With LVP or Laminate
- • Visible dips and bumps
- • Locking mechanisms fail
- • Squeaks develop
- • Premature wear on high spots
The Rule: Spend 20% of your time on subfloor prep and 80% on installation, not the other way around. A perfect subfloor makes the actual flooring installation dramatically easier.
Step-by-Step Subfloor Preparation
1. Remove Old Flooring Completely
Take up everything down to bare plywood subfloor. This includes old vinyl, tile, underlayment, adhesive, staples—everything.
Complete Removal Checklist:
- Old flooring material removed
- Old underlayment removed (if present)
- All staples and nails pulled or pounded flat
- Adhesive residue scraped off
- Floor swept and vacuumed clean
Asbestos Warning: If your home was built before 1980 and has old vinyl flooring or mastic adhesive, test for asbestos before removal. Professional abatement may be required.
2. Inspect for Damage and Squeaks
Walk the entire floor slowly, looking and listening for problems. Mark problem areas with painter's tape so you don't miss them.
What to Look For:
Soft or Spongy Spots
These indicate water damage or rot. Must be replaced.
Squeaks and Creaks
Caused by subfloor movement on joists. Mark these areas to screw down later.
Delamination
Plywood layers separating. Feels spongy and must be replaced.
Stains or Discoloration
Could indicate past or present water issues. Investigate the source.
3. Check for Level Across the Floor
Use a long straightedge or 6-foot level to find high and low spots. Check in multiple directions (side to side, front to back, and diagonally).
Levelness Requirements by Flooring Type:
Pro Tip: Mark high spots with an "H" and low spots with an "L" using chalk or pencil. Draw arrows pointing toward the lowest part of dips to help when applying leveling compound.
4. Fix Squeaks and Secure Loose Areas
Eliminate squeaks now, because you can't fix them after the new floor is down. The solution is to pull the subfloor tight to the joists.
How to Fix Squeaks:
- 1.
Locate the floor joists
Use a stud finder or look for existing nail/screw patterns. Joists typically run 16" on center.
- 2.
Drive screws along squeaky areas
Use 2" deck screws every 6-8 inches along the joist. The screw should penetrate the joist by at least 3/4".
- 3.
Don't overdrive screws
Screw should be flush or just below the surface, not creating divots in the plywood.
5. Level Uneven Areas
Now address those high and low spots you marked. Low areas get filled; high spots get sanded or planed down.
For Low Spots (Most Common):
- 1. Vacuum low areas thoroughly (no dust or debris)
- 2. Apply primer if required by leveling compound manufacturer
- 3. Mix self-leveling compound per package directions
- 4. Pour compound into low areas, starting at the lowest point
- 5. Use a trowel to spread, but don't overwork—it will self-level
- 6. Allow to cure completely (24-48 hours typically)
For High Spots:
- • Small bumps: Sand down with coarse sandpaper or belt sander
- • Larger high spots: Use a power planer, removing material gradually
- • Ridge at subfloor seam: Sand or plane flush, then secure with screws
6. Replace Damaged Sections
Any area with water damage, rot, or delamination must be cut out and replaced. There's no shortcut here.
Subfloor Replacement Process:
- 1. Mark cut lines centered on joists (you need solid wood to screw into)
- 2. Set circular saw depth to plywood thickness (usually 3/4")
- 3. Cut out damaged section, being careful not to cut into joists
- 4. Clean the opening, removing all debris
- 5. Cut new plywood patch to fit (same thickness as existing subfloor)
- 6. Apply construction adhesive to joists
- 7. Install patch and screw every 6" into joists (2" screws)
- 8. Fill gaps around patch with self-leveling compound if needed
Tools and Materials You'll Need
Tools
- • 6-foot level or long straightedge
- • Cordless drill/driver
- • Circular saw (for subfloor replacement)
- • Shop vacuum
- • Pry bar and hammer
- • Belt sander or power planer
- • Mixing bucket and drill attachment
- • Trowel for spreading compound
Materials
- • Self-leveling compound ($30-50 per bag)
- • 2" deck/construction screws (1 lb box)
- • Plywood patches (if needed, same thickness)
- • Construction adhesive
- • Primer for leveling compound (if required)
- • Painter's tape for marking
- • Dust mask and safety glasses
Common Subfloor Prep Mistakes to Avoid
Skipping the Level Check
"It looks flat" isn't good enough. Always verify with a level. Even small variations will telegraph through LVP or crack tiles.
Installing Over Old Adhesive
Old mastic, construction adhesive, or thinset must come off. It creates an uneven surface and prevents proper adhesion.
Not Letting Leveling Compound Cure
Don't rush this. Walking on or installing over uncured compound causes cracks and adhesion failure. Wait the full cure time.
Ignoring Water Damage
Never install new flooring over water-damaged subfloor. Fix the source, replace the damaged section, and ensure it's completely dry first.
Frequently Asked Questions
How level does a subfloor need to be for tile or LVP?
For tile installation, the subfloor should be within 1/8 inch over 10 feet. For luxury vinyl plank (LVP), it should be within 3/16 inch over 10 feet. Laminate and engineered hardwood are most forgiving at 3/16 inch over 10 feet. Use a long straightedge or 6-foot level to check, and use self-leveling compound to fix low spots.
How do I fix squeaky subfloor before installing new flooring?
Drive 2-inch screws through the subfloor into the floor joists below, spacing them every 6-8 inches along squeaky areas. The screws pull the subfloor tight to the joists, eliminating movement that causes squeaks. If you have basement access, you can also add blocking or apply construction adhesive between joists and subfloor from below.
Do I need to replace water-damaged subfloor?
Yes, water-damaged subfloor must be replaced. Signs include soft or spongy areas, visible mold, delamination (plywood layers separating), or a musty smell. Cut out damaged sections back to solid material and replace with new plywood of the same thickness. Address the source of water damage before proceeding with new flooring.
Can I install new flooring over old vinyl or linoleum?
Sometimes, but it's not recommended. Old vinyl can hide subfloor problems and create an uneven surface. If the vinyl is well-adhered, flat, and only one layer, you might install over it with proper underlayment. However, removing it ensures better results. Note: vinyl installed before 1980 may contain asbestos—test before removal.
What is self-leveling compound and when do I need it?
Self-leveling compound is a cement-based product that flows like liquid but hardens flat and level. Use it to fill low spots, dips, or uneven areas in your subfloor before installing tile, LVP, or laminate. It's essential when your floor has variations greater than 3/16 inch over 10 feet. Apply it according to package directions and allow full cure time (typically 24-48 hours).
Ready for the Next Step?
With your subfloor level and solid, it's time to install the underlayment that will provide moisture protection and sound dampening.