Moisture Control: Why Wet Wood Decides Termite Risk

Where water comes from

Water reaches the wood in a small number of predictable ways, and each one can be found on a walk around the building.

A walk after rain is the most useful inspection a household can do. Look at where water runs, where it pools and where the ground stays wet longest. Those are the spots to measure and to change.

• A downspout that discharges at the foundation or into a bed beside the wall
• Grade that slopes toward the building instead of away from it
• An irrigation zone that waters the wall, the sill or a bed against the siding
• A leaking hose bib, a pipe in the crawl space or a drain that backs up
• A low corner of the lot that holds rain after a storm

What to measure, and how to read it

A moisture meter gives a reading at each point, and the readings show which spots hold water and which are dry.

A technician uses a moisture meter on the wood and the masonry around the building, at the sill, at the base of the wall, in the crawl space and beside any downspout. The readings are recorded by location, so the same spots can be checked again after a change.

A single high reading is a reason to look further, not a diagnosis. A pattern of high readings across a corner, a run of wall or a bed is the sign that the water is coming from a specific source.

Moving the water

The first change is to move the water away from the building, because wood that stays dry is much less attractive to termites.

Extend downspouts so they discharge well away from the foundation, and check that the splash block or the extension sends the water downhill. Regrade the soil near the wall so it falls away from the building, and fill any low spot that holds water. These changes are often simple, and a landscaper or a handyman can make them.

Irrigation is often the hidden source. A zone that waters the bed against the wall, or a sprinkler head that hits the siding every morning, keeps the wood wet. Move the head or the zone, and check the readings after the change.

Keeping wood and mulch off the soil

Wood in contact with the ground is the link that lets a colony reach the building, and mulch piled above the siding is a similar route.

Keep wood steps, deck posts and fence rails on a concrete or metal base, with a gap of soil or gravel between the wood and the foundation. Pull mulch below the first course of siding. Stack firewood away from the house, off the ground, and not against a wall.

The MSU Extension 2006 newsletter says that long-distance spread of termites is mainly through infested wood products, and that many northern detections came from railroad crossties used as landscape timbers. A timber bed is therefore a route to check, as well as a source of moisture.

The crawl space and the drying routine

A damp crawl space keeps the sill and the joists wet from below, and it is often the last place a household looks.

Check the crawl space after heavy rain, and look for standing water, damp insulation and a dripping pipe. A vapor barrier on the ground, good ventilation where the building is designed for it and a repaired leak are the usual fixes. The technician will say which is needed and whether a specialist is required.

Do not seal the vents of a crawl space without advice. Closing them can trap moisture and make the wood wetter. The right change depends on the building and the source of the water.

The seasonal pattern of moisture in DeSoto County

Moisture is not constant through the year, and the readings are highest after the wet periods the MSU Extension notes for the swarm season.

MSU Extension links Formosan swarming with daytime rain, and the same rain is what loads the ground and the wood. A household that takes its first readings after a wet week in spring will see the highest numbers of the year, and a dry week in late summer will show the lowest. The reading is useful at both points, because the difference shows how much water the building is taking in.

A reading taken only once a year can mislead. The technician takes readings after rain where possible, and the household is asked to note the weather at each check. The log then shows whether the building is wetter after storms and whether a drainage change has reduced the difference.

Gutters, downspouts and roof runoff

A roof sheds a large volume of water in a short time, and a gutter that is blocked or a downspout that discharges at the wall can put that water exactly where a colony needs it.

Clean the gutters twice a year, and check that the downspouts discharge onto a splash block or an extension that sends water at least a short distance away from the foundation. A downspout that empties into a bed beside the wall will keep the wood wet through a season. The fix is an extension and a regraded strip of soil, not a sealant on the wall.

Check the roof runoff during a heavy shower. Look where the water lands, how fast it drains and whether it runs back toward the building. The place where it pools is the place to measure, and the place where the technician will look first.

Firewood, mulch and timber rules for a household

Wood and mulch piled against the building are the simplest moisture and termite routes to remove, and the rules are short.

The rule is not to remove all wood from the yard. It is to keep wood from touching the soil and the building at the same time, and to keep the moisture around the wood under control. A timber bed that is raised on a non-wood base and kept dry is a much lower risk than one on the ground.

• Keep firewood away from the house, off the ground, and not against a wall or a fence that touches the foundation
• Keep mulch below the first course of siding, and pull it back from the corner of the building
• Do not reuse railway ties or thick landscape timber as a bed edge beside the house without checking it
• Replace any soft or eaten timber, and keep the replacement off the soil
• Check any timber brought onto the property for mud tubes before it is placed

A monthly routine that keeps the readings low

A short monthly routine catches most moisture problems before they reach the wood, and it takes less time than a single repair.

Once a month, walk the outside of the building after any rain and look at the downspouts, the grade, the irrigation heads and the bed edges. Once a season, take a moisture reading at the sill and at the base of the wall, and write it in the log. Once a year, check the crawl space and the cellar for standing water, damp insulation and a leaking pipe.

A household that does this routine has the record it needs if a technician or an insurer asks about the moisture. It also has an early warning. A change in the readings is often the first sign of a new leak, and it is much cheaper to fix a leak in its first month than in its third season.

Crawl space ventilation and the trade-off

Ventilation and moisture are linked, and the right balance depends on the building, the climate and the source of the water, so the change should be advised rather than guessed.

Many crawl spaces are ventilated to let moist air out, and closing the vents can trap that moisture against the wood. The alternative is a ground cover over the soil and a dehumidifier or a drainage change, which keeps the air drier without relying on the vents alone. The technician or a qualified specialist will say which approach fits the building.

The household should not close or open vents on its own initiative. A change made in the wrong direction can add to the problem, and the report should record the change and the reason for it.

Measuring after a change

A moisture change is only proven when the readings are taken again at the same spots, after the same kind of rain, and recorded alongside the earlier numbers.

Choose the spots at the first visit and mark them on a sketch. At each later check, take the reading in the same place, using the same meter setting, and note the weather in the previous day. A drop in the reading after a downspout has been extended is good evidence that the change worked. A rise after a heavy rain is not a failure, but it is a reason to look at the next source of water on the list.