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Short Summary
Main recommendation: You can tile directly over concrete, but in basements or older concrete slabs without reinforcement, the speaker recommends first using a crack isolation layer, such as a roll-on uncoupling membrane (Mapei) or a Schluter uncoupling membrane. The speaker notes that concrete in colder zones, such as the Midwest, Northeast, and Canada, is often poured on gravel without reinforcement and is more prone to cracking.
Key Points
- Reinforced concrete slabs are less susceptible to cracking than unreinforced ones, so the need for protection depends on the slab's construction.
- Basement concrete in North America's higher-zone regions is often poured on gravel with no reinforcement, making it crack-prone.
- Apartment concrete is generally less of a cracking concern because it is typically reinforced with steel.
- Most concrete can crack slightly, so the roll-on membrane protects in most cases, but basements warrant a fuller crack isolation approach.
- The speaker frames the decision around the risk of future damage: a small tiled area can end up affected if the foundation cracks through it.
Details Worth Noting
- Concrete instructions: For a roll-on uncoupling membrane, paint it onto the concrete, let it sit overnight, and tile the next day.
- Concrete instructions: Find the Mapei roll-on product at Floor and Decor, a local tile supply store that carries Mapei, or via the Mapei website's dealer locator.
- Concrete instructions: For a sheet-style crack isolation membrane, buy a roll from a local store and cut a piece to the needed size, which the speaker says is usually small in a bathroom.
- Concrete instructions: Assess your home first by checking its age, whether it has a basement, and whether the slab is reinforced, since these factors determine how much protection is needed.
- The speaker says for a few bucks you can get crack isolation protection for a small bathroom.
- The speaker's example uses a 25 square foot bathroom and asks whether it's still only 25 square feet if the foundation cracks right down the middle.
- The speaker describes the roll-on membrane as sufficient for most cracking, excluding severe foundation movement.
Bottom Line
Whether a membrane is needed depends mainly on the slab: reinforced or apartment concrete can often be tiled directly, while unreinforced basement concrete is better protected with a crack isolation membrane.
