There’s increasing evidence that mold and rot may be builders’ biggest enemy. These moisture-caused blights can lead to premature structural deterioration, shorten the life of exterior claddings and paints, foster infestations — and lead to costly litigation.

As extreme weather becomes more common, and the health hazards related to rot and mold become more widely known, builders can no longer afford to slough off these concerns.

Fortunately, a growing body of building products and systems are available that make it easier to prevent mold and rot than ever before — if builders avoid three common pitfalls. Here’s a look at the three key mistakes builders make that foster mold and rot and how to avoid them.

1. Failing to create a drainable space. The best protection against moisture may be a new generation of housewrap called drainable housewraps. The drainage channels in these wraps give water an unobstructed path to escape from behind the cladding. This drainage space helps eliminate ponding along siding edges that can occur with traditional housewraps, which can lead to mold and rot. Installation errors can also cause drainage problems since most wraps must be installed in a certain direction to work properly. But omnidirectional wraps work no matter what direction they’re installed. This feature comes in handy when working around odd shapes or bump outs.

2. Failing to shingle lap. To work properly, housewrap must be installed in shingle lap fashion. Shingle lapping should begin at the base of the wall assembly with the housewrap a minimum of 2 inches over the sill plate. All horizontal seams should be overlapped by at least 6 inches, all vertical seams by at least 6 inches and corners by 12 inches. A double-sided taping system is another way to promote continuous drainage down the wall. The double-sided tape is applied on one part of the paper with another paper overlapping in shingle lap fashion. This extra step is another way to prevent mold and rot.

3. Using makeshift mounting blocks. When it comes to openings for vents and electrical, many builders simply tape around the opening and cover it with a makeshift treated piece of lumber. But that slipshod method often creates a weak spot for moisture to enter the structure — and an invitation for mold and rot. Specially designed mounting blocks that are installed similar to window headers prevent this outcome. These molded plastic mounting blocks come in a variety of configurations with built in flanges, flashing and slope to protect against moisture and encourage proper water runoff.

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