How To Look At A House
McGarry and Madsen's home inspection blog for buyers of
site-built, mobile/manfuactured and modular homes
Where are the most common places to find wood rot on a house?
Thursday, June 21, 2018
Here’s our “Top 10” list of hotspots where wood rot is likely to occur on the exterior of a house:
- Will it rot or not? - The first thing to do is determine what is wood or a manufactured cellulose product and what is inorganic and not subject to wood rot. Just because a house has cementitious siding (such as HardiPlank®) does not mean there is no exposed wood on the exterior. Some homes will have matching cementitious trim, while other builders use PrimeTrim® or a similar composite manufactured wood trim, and there can also be pressure-treated wood trim—which is rot-resistant but will eventually succumb.
- How close is it the ground? - Wood near the ground is always more likely to develop wood rot before areas higher up on the wall. Splash-back of rain falling off the roof onto the wall and moisture evaporating from the ground mean that any wood touching the ground or within 6 inches of it should be examined carefully, and probed for soft areas if necessary.
- Look for water traps - All the surfaces on the exterior wall of a home should slope away from the wall so that any rain that hits the wall will drain away. Areas that are flat or—even worse—slope backwards will allow water to puddle on them or funnel it back into the wall. Carpenters call them “water traps” and put a slight slant in any near-level surfaces. Window sills and the top of trim over a window are classic water trap locations to check.
- Deteriorated paint - Keeping water from penetrating the surface of wood is one of the key functions of paint. Wood is more vulnerable when it is gone.
- End-grain wood - Wood is more absorbent of water at the end-grain. The side trim of the widow below is rotting from the bottom up because the bottom trim is a water trap and standing water seeps under the unsealed joint between the two pieces of wood.
- No flashing over windows and doors - If a builder uses caulk to seal the top of window trim, eventually the caulk will fail and the opening will funnel water behind the trim. Show below is the correct way to flash the top of a window.
- Behind gutters, downspouts and under drip strips - Whenever there is a surface in front of wood that water can get trapped behind, look carefully there.
- Decks, stairs and railings - The combination of weather exposure and complicated intersecting surfaces makes these outdoor structures attached to a house prime suspects for rot.
- Inside Corners - Because a lot of water often comes off the roof at an inside corner, you can expect problems below it.
- Deteriorated and Missing Caulk - Gaps in caulking not only lets water in, it often traps the moisture in place.
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