An addition settling can be caused by soil shrinkage as it dries. Get moisture to the dirt below the footings.
When the water-table drops during a drought the soil shrinks as it dries. Put an addition over 48-inch footings next to a house over 8-foot footings and it will settle as the soil below the addition dries. Even though they are attached, they become two separate buildings. The point of attachment becomes the telltale that there is a problem.
What happens is the back room pulls away from the main house. The sidewall windows and doors on an addition are unusable. The addition is on four-foot footings next to a house on eight-foot footings. A crack develops between the house and the addition. The crack is small at the base and gets larger at moves up to the roof. The roof and flashings are stretching and ceiling leaks are only a short time away.
What can we do to remedy the problem?
Get moisture to the soil below the footings with out washing them out.
Here are some home remedies that have returned some success.
Run soaker hoses around the settled area and run them several hours a day. Do not place hoses closer than four-feet of the main house. You do not want water finding a path to the house weep tiles. It could undermine the addition’s footings.
Bore three-inch postholes around the addition down a foot below the footings. Sleeve the holes with two-inch PVC pipe with holes drilled in the bottom twelve inches. Fill the pipe with pea-stone and flood them with water twice a day. You still have to stay 4-feet away from the main house.
A trench can be dug along the outside wall of the addition and filled with water a couple times a day. Watch that the “moat” does not flow to the main house.
Dear readers, none of these suggestions will guarantee that this will cure your settling dilemma. It should stop the settling; possibly gain you back some distance.
Other choices are to get a general contractor capable of lifting or repairing your condition. Several are available in our area and from past experience I suggest getting quotes from as many contractors as possible.