Floor leveling & substrate prep.

A 1620 × 3240 mm porcelain slab is unforgiving. So is a 60 × 60 cm Calacatta on a 12,000 sq ft floor plate. The slab is only as flat as what you set it on.

We level the substrate before we set anything on top of it. The work below — scanning, drying, priming, pouring — is the work that determines whether the joint reads as 1.5 mm or 4 mm three months after the homeowner moves in.

How we set the floor before we set the floor

1 · Substrate scan

We laser-survey the slab against a 3 m straightedge before anyone unloads a pallet. Highs are mapped, lows are flagged, and any out-of-spec sections of the slab — common in older Brickell towers and 1980s Coral Gables remodels — are noted on the proposal. No surprises billed mid-project.

2 · Moisture and RH test

Concrete in Miami runs wet. We RH-probe per ASTM F2170, 40 mm into the slab, and document the result before any underlayment goes down. Anything above 75 % RH gets a vapor reduction layer (LATICRETE NXT VR or equivalent). Anything above 90 %, we wait — and the proposal already accounts for it.

3 · Primer

Open-cell concrete drinks self-leveler. We prime with the system primer matched to the SLU — every time. Skipping this step is the most common reason for delamination and chalking under porcelain six months later.

4 · Self-leveling pour

We pour Sika Level-50 (or LATICRETE NXT Level when the schedule needs faster cure) at the depth the survey called for — anywhere from 6 mm to 25 mm. Two crew on the bucket, one on the rake, one on the spike roller. Continuous pour, wet edge maintained, no cold joints across a great-room slab.

5 · Rake, pin, sign-off

We pin the cured pour against the straightedge before any tile lands. ± 1.5 mm over 3 m is the spec we hold ourselves to — written on the sign-off sheet, walked with the homeowner or the GC, signed before install begins.

Partner systems we set every day

• LATICRETE NXT Vapor Reduction — single-coat RH barrier rated to 100 % RH. The system we reach for over post-tensioned slab and any below-grade pour.
• Sika Level-50 — high-flow self-leveler that cures hard enough for porcelain in 24 h. Our default for renovation timelines.
• Schluter Ditra-XL — 7 mm uncoupling and waterproofing membrane over plywood subfloors and Schluter Ditra-Heat radiant systems.

Where this matters most

Brickell high-rise post-tensioned slabs run 4–8 mm out of tolerance over a great room. Coral Gables 1950s pours have crowned. Key Biscayne sea-air slabs hold residual moisture. Pinecrest additions seam with original construction at the threshold. Each of these gets a different specification — and we put the spec on paper before we quote the install.

What the spec sheet should say

If you are an architect or designer specifying our install, three lines on the substrate page are enough:

Substrate to be flat to ± 1.5 mm over a 3 m straightedge prior to install. RH to be tested and documented per ASTM F2170; vapor reduction membrane required above 75 % RH. Self-leveling underlayment manufacturer and primer to be approved in writing by the slab manufacturer’s technical team.

We will hit those three lines, we will document each one, and we will sign off the floor with the GC before the first slab lands.