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Don't skimp on surface preparation. You must get the foundation wall and footing clean, free of loose material, and fairly smooth. Do as much as you can ahead of time: Once you start waterproofing, rhythm is crucial, and you don't want to have to stop to scrape loose concrete from the footing or break off a form tie.

Waterproofing materials aren't designed to cover large voids or honeycombs. You'll need to fill these, preferably with nonshrink grout or a good patching cement. You may be able to patch form-tie holes or smaller voids with trowel-grade mastic. Check the manufacturers instructions to make sure that whatever material you use for patching is compatible with the waterproofing product.

Waterproofing likes a clean wall. Here's what I recommend for a surface preparation procedure:

Survey the entire surface to be waterproofed. Identify special problems, such as water on footings, concrete forms not removed, footings not dugout, and pipe penetrations not prepared. Have these problems worked on right away, especially if these areas are the responsibility of another trade.

Dry off all footings. A big propane torch with a 20-pound tank is good for this. For puddles, sweep standing water off with a broom, then dry the damp spot with the torch.

Remove concrete form ties. If there's an odd form tie that wasn't aligned properly and won't break off flush, cut it off with a cutting torch or reciprocating saw. Break form ties off on the inside of the foundation too. Another waterproofer once told me that on one of his jobs the general contractor sent in a laborer, after waterproofing was applied, to break off form ties on the inside of a foundation. The laborer decided it would be easier to just pound the ties back into the wall. Every one of them punched through the waterproofing membrane on the other side, which was already backfilled.

Scrape off excess and loose material from walls and footings. A long-handled ice breaker is good for this. Some waterproofing manufacturers will require you to machine-grind any ridges or protrusions before applying their products. It's good to have a brick hammer on hand, too. Pay special attention to the footing. Quite often, puddles of congealed slurry form on the footing when the wall is poured. This material doesn't have the full strength of concrete, it isn't bonded to the footing, and should scrape off easily.

Sweep off the walls and especially the footings. They don't have to be clean enough to eat off of, but don't leave a film of dust or mud. Waterproofing materials won't stick to a dirty surface. Keep other trades and workers out of the area. Besides the safety hazards, other workers tend to be oblivious to what waterproofers are trying to accomplish. Many times I've cleaned a footing, only to see a muddy-booted laborer stride right down its length, leaving tracks the whole way.

Take care of any patching or filling. Grout around penetrations and follow any other instructions from the waterproofing manufacturer that apply at this point.

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