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Danny141035 t1_iyburcy wrote

UM should go tight within reason to the drywall 1/4”-1:8” gap. You would never run UM vertically. What your seeing vertically is a fleece lined waterproofing membrane. The 2 most common products for this are made by Schluter Ditra (UM) and kerdi (waterproof membrane) in a basement there is absolutely no need to use the fabric membrane on the wall, it’s mostly used in showers and bathroom floors. Be sure to honor the control joints cut into your concrete slab. Otherwise they will in time translate to the tile above and crack them. TCNA section EJ 171

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marshgirl12 OP t1_iycjrqf wrote

I’m not familiar with control joints, the concrete is also pretty old. Could you provide more guidance?

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Eyiolf_the_Foul t1_iyctr9o wrote

They are to control cracking in the slab as it cures-you may not have any in your basement. If the slab is in good shape just apply your membrane over the whole surface.

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bassboat1 t1_iydjla9 wrote

Control joints are cast-in-place (look down the next time you're on a sidewalk), or sawn after the concrete has hardened (often on a 10' or 12' grid). It's expected that a concrete slab will shrink as it cures and inevitably crack. The control joints will (hopefully) limit the cracking to the grid and not occur randomly, at angles, etc... Fiber additive or welded wire mesh is embedded in the concrete to help prevent the now separated pieces from moving vertically with respect to each other. The uncoupling membrane prevents the cracks from telegraphing through bonded materials like tile. On large slabs, expansion joints are required, and they should be continued up through the tile as a caulk joint.

Do not run Ditra or the fleece products like Redgard/Custom up the wall. Kerdi can be run up the wall in some shower systems.

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