How to Waterproof Exterior Walls Between Buildings

Interior building leaks do not always connect directly with an outside source. Repairing an entire exterior wall is often the best solution to recurring minor leaks inside. While professionally applied hot and cold "waterproofers" may require scaffolding, more manageable do-it-yourself materials rely on cold adhesives and impermeable fabric coverings. With some planning and, ideally, a helper, a homeowner can use these recently developed waterproofing materials to protect exterior building walls from weather damage.

Power sander with steel brush
Protective eyewear, gloves and clothing
Measuring tape
Carpenter's level or T-square
Utility knife
Ladder(s)
Trowel, brush or recommended adhesive applicator
Wallpapering finish-brush or other broad stiff-bristled brush
Cold adhesive for wall membrane
Waterproof membrane fabric
1 or more helpers, optional but desirable

Instructions

- 1
  Remove any paint or other loose surfacing on the building wall, using power or hand removers. Brush the surface clean of dirt and paint flakes before applying adhesive.
- 2
  Measure and cut a manageable segment of waterproofing membrane. If you're working alone with a single ladder, cut segments 4 to 6 feet wide and 6 to 8 feet long. Fabric should snug up to but not cover window trim, drains or power connections. Using a level or T-square will produce more accurate cuts around windows and other openings.
- 3
  Spread adhesive with a trowel, stiff brush or other applicator recommended by the manufacturer. Cover the surface completely with a smooth, even layer of adhesive, approximately 1/4-inch thick.
- 4
  Press the waterproofing membrane firmly into the adhesive. Smooth the membrane into the adhesive using a finish brush to prevent loose sections of fabric.
- 5
  Plan a 1-inch overlap between pieces of waterproofing membrane, spreading adhesive over the seams between new and previously applied sections. Seal the seam with additional adhesive if needed. Your goal is to prevent gaps that can be penetrated by water.
- 6
  Let the building surface cure and dry completely, up to two weeks in variable weather. This surface can be painted with any latex- or oil-based paint formulated for use on exterior masonry.

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