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Prep

Subfloor Prep and Floor Leveling on Long Island

The most important part of tile is the part nobody sees. Floor prep is what decides whether tile cracks in three years or holds up for twenty.

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What proper subfloor prep includes

Cement board over plywood, uncoupling membrane where movement is expected, crack isolation on slabs, self-leveling underlayment when the subfloor is out of tolerance, and proper fastening so nothing flexes under the tile.

Why this matters for large-format tile

The bigger the tile, the less forgiving the floor is. Large-format demands flatter substrate than smaller tile. We measure with a long straightedge before quoting so the prep matches the tile choice.

A red brick wall under construction with tools and materials scattered around in a renovation project.

FAQ

Subfloor Prep and Leveling — Frequently Asked Questions

Do you do self-leveling pours?
Yes — when the subfloor needs it for the tile size and look we are installing.
How flat does the subfloor need to be for tile?
Industry standard is 1/8" variation in a 10-foot span for standard tile and 1/16" in 10 feet for large-format. We measure with a long straightedge before we start. If it’s not there, we level — full stop. This is the most common shortcut bad installers take and the biggest cause of cracked tile.
When do you use self-leveling underlayment?
When the subfloor is out of flat beyond what thinset can compensate for, or when the floor has dips, sags, or settled spots. Self-leveler creates a uniform substrate that’s ideal for large-format porcelain.
Do I need cement board on a wood subfloor?
For most Long Island homes with wood-frame floors, yes — either cement backer board or an uncoupling membrane like Schluter-DITRA. Tile bonded directly to wood will crack as the wood moves seasonally.
Can you add insulation under the tile floor?
Some membranes (Schluter-DITRA-HEAT) include radiant electric heat. For thermal insulation specifically, we can install cork or foam underlayment under the substrate. Long Island basements especially benefit from this.

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Get a free estimate for subfloor prep and leveling

Long Island Tile Pros covers Nassau and Suffolk County. Send us a few details and we will follow up with next steps.

Request a Free Tile Estimate Call (631) 346-6054
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