Water in a house, Good Thing, Bad Thing? Some places like the sink you expect to find water. Other places like the floor, water is a problem. Builders work hard to build a home so water says where it belongs.
Look at the way the roof is installed! The shingles are layered from bottom to top. They are also lapped over each layer. So water, will drain down the roof and off. If water gets up under a shingle, the roofing crew has done some other things like roofing felt, metal valleys and flashing to do the job.
Look at the water run off the overhang in the top picture. When it rains most of the water hits the roof, the overhang changes how much strikes the wall. Matt Risinger, a home builder in Austin, TX, tweeted this graphic recently.
Do you think Matt builds homes with short overhangs?
The layers on the roof are repeated for the same purpose for other areas of the house. They work the same way. Some are installed the same way, some are installed differently. Other areas of your home have a different experience with water.
The outer layer of a wall, the siding, like the shingles, are lapped. The next layer behind the lapped siding is usually known as house wrap. That’s the white covering you see on many new homes, before the siding is installed. Technically, the term for this is ‘Weather Resistant Barrier’ or WRB. Just as the roofing felt helps keep water outside on the roof, the WRB helps keep water outside on walls.
Just as the roofing felt, shingles, and siding are lapped; house wrap should also be lapped, each new layer draining onto the top of the layer below. The directions call for a 6 inch lap, and then tape. The tape is used on house wrap and not roofing felt, because it is a different material, cap nails should be used.
How does the home buyer know the house wrap is right? It passed a code inspection, didn’t it? This image shows damaged house wrap. Is it taped and lapped correctly? Are the fasteners used according to the manufacturer’s directions.
Do these problems mean that house wrap is bad. Certainly not! House wrap is a great product when installed correctly. It will do the job it is designed to do; act as a Weather Resistant Barrier. It will then, direct water back outside and not allow it into the wall.
Windows and doors need an opening in the wall. These openings must be detailed correctly or water will enter. These details involve flashings, and tapes. How the window is made, with nailing flanges, with foldable nailing flanges or field installed nailing flanges must be considered. Here we see a tape used to seal the nailing flange to the house wrap.
Is house wrap the only type of WRB used? No! It is the most widely used in this area. The others will be covered in a future post.
Now if the roof and the wall properly shed water, and they guide any water that gets inside back out, we get to the ground. At this point the water should be directed away from the house. Gutters and down spouts do a great job when the ground slopes away. Recommended slopes are 1/4 inch per foot for hard surfaces like concrete, and 1/2 inch per foot for other surfaces. Local codes may require more, or a builder preference may result in a larger grade.
The basement or foundation walls should be damp-proofed on the outside. This is the black spray applied to the concrete. A tile drain system is installed around the exterior of the foundation and tied into a sump to be pumped out of the home.
If these or other equivalent measures are built into a new home, the builder is doing the job right. They are all in the building code. The issue is not what material, the issue is quality of workmanship.
This post is part of a series of posts on A Healthy Home.