Installation
Installing Large Format Tile on Texas Post-Tension Slabs & Clay Soils
Short answer
Texas clay soils shrink and swell, and most new homes sit on post-tension slabs. Large format tile performs well on them if you never drill into tendons, isolate existing cracks with an uncoupling membrane, install perimeter and field movement joints per TCNA EJ171, and moisture-test the slab first.
Why Texas soils matter
From the Blackland Prairie around Dallas to the Gulf Coast clays under Houston, much of Texas sits on expansive soils. They swell when wet and shrink in drought, which moves foundations seasonally. Large tiles span more of that movement, so the installation must be designed for it.
Post-tension slab rules
- Never core or anchor blindly. Steel tendons under high tension run through the slab. We locate them before any fastening and prefer bonded membranes over screws.
- Map existing cracks. Shrinkage cracks are normal; we treat them with crack-isolation membranes rather than ignoring them.
- Test moisture. New slabs can emit moisture for months; we RH-test and select vapor-tolerant setting systems.
Uncoupling and crack isolation
An uncoupling membrane such as Schluter Ditra lets the slab move slightly without transferring stress into the tile. It helps protect 24×48 and 48×48 floors in open floor plans.
Movement joints — the step most often skipped
TCNA method EJ171 calls for movement joints at the perimeter, at changes of plane, over structural joints and in the field — typically every 20–25 ft indoors and 8–12 ft in areas exposed to sunlight. Skipping them is the leading cause of tented or cracked tile in Texas sunrooms and patios.
Learn how we handle conditions in your area on our service area pages.