Where does the water under a pier house come from?
It comes from the ground rising through a dirt floor, from storm water that runs in through vents or gaps, from a broken line or drain beneath the house, and from a flood that reaches the low part of the lot. Each source leaves its own pattern on the wood.
Water from the ground rises through a dirt floor, and it is worst after a wet spell. Storm water enters through a vent, a gap around a pipe or a broken foundation joint, and runs to the lowest point. A split line or a drain beneath the house puts water directly onto the ground, and the wood beside it is the first to take it up.
The pattern is the clue. A line of damp along the sill suggests outside water, a stain around a pipe suggests a leak, and a damp floor across the whole space suggests moisture from the ground. The readings are taken with that pattern in mind.
Why does a damp crawl space affect the rooms above?
The joists and subfloor take moisture from the air and from the wood below them, and the moisture reaches the finish floor above. The floor may cup, sag or stain even when the room above looks dry.
Wood holds moisture in its fibers and changes size with the air around it. A subfloor that takes in damp from a crawl space swells at the seams, and the finish floor above is pushed up. Hardwood cups, vinyl ridges and carpet feels soft over the same area.
The rooms above are checked from both sides. The floor is read from the top and the joists from below, and the two sets of readings are compared so that the plan covers both.
Should a vapor barrier be added after the water?
It depends on the ground, the drainage and the house. A torn barrier should be replaced, and a new one is a decision the owner makes with a contractor who works on crawl spaces.
A barrier that has torn, floated or been laid loosely lets moisture through. A torn barrier is noted in the record and its replacement is a separate job. A barrier does not stop water that comes in from outside or from a broken line, and it does not replace drainage around the house.
The restoration work does not decide whether a barrier is installed. It records the condition of the ground and the existing barrier, and the owner decides whether to ask for one.
What is left to repair after a crawl space loss?
The source, the framing, the subfloor and the finish may each need repair. Those repairs are made by the trades that own them, after the drying readings are complete.
A broken line is repaired by a plumber. A sill plate that has rotted is replaced by a carpenter who knows the framing, and subfloor boards that have swollen or split are replaced. The finish floor is repaired or refinished after the readings show the wood is dry.
Closing the access too early is a common mistake. The readings should be dry for the full period in the plan before the crawl space is closed, and the record should be kept with the rest of the house's file.
How are the joists tested before the floor is closed?
The joists are read along their length at the sill, the midspan and the bearing on each pier, since moisture often stops at one point and not the whole joist. Each reading is recorded, and the floor is not closed until every point is at goal.
A joist that stays high at one point can be the sign of a continuing leak or a damaged pier, and the readings flag it for a trade to check before the finish goes back.
