Dear Mr. and Mrs. Wilson:

At your request, we performed a structural inspection of your house on September 4, 1998. Mrs. Wilson was present during the inspection. The purpose of the inspection was to investigate the cause of cracks in the brick veneer on the front and rear elevations and determine what should be done about the problem. During our field inspection, we observed the exterior walls, the topography around the house, the crawl space, attic, and the interior on the first and second floors. We did not perform any excavations or do any intrusive investigation work. For purposes of the discussion below, all directions are in relation to a person facing the front of the house.

DESCRIPTION OF THE HOUSE

The house is a two-story colonial with a hip roof. It is approximately 10 years old. The Wilsons purchased it in 1995. Its dimensions are about 40' long by 30' wide, with a total living area of 2400 sq. ft. The house has a pier and curtain wall type foundation, wood frame superstructure, and brick veneer cladding. A brick fireplace chimney is located on the right end of the house. The ground slopes gradually from left to right to within 10'-12' of the end of the house, then it pitches down sharply. The ground in the crawl space slopes similarly to the ground outside. There is about 2' of headroom on the left end of the crawl space and about 6' of headroom on the right end. Although we did not observe any water in the crawl space during our inspection, it is likely that some water accumulates at the low end of the crawl space during periods of heavy or sustained rain.

DESCRIPTION OF THE STRUCTURAL DEFECTS

There is a vertical step crack in the brick veneer on the rear wall on the right corner. The crack extends the full height of the wall. The crack is wider at the top and diminishes to near zero at the foundation. As it moves up the wall, it fans out into several cracks. The sum of these cracks being about ½ ".

There is also a similar vertical step crack in the brick veneer on the front wall at the right corner. The crack extends the full height of the wall, is wider at the top, and diminishes to zero at the foundation. It is about ½" wide at the top. The location of the cracks corresponds somewhat with the points where the grades change in the front and back of the house.

Mrs. Wilson said that she and her husband first became aware of the cracks about 1-½ years ago, when they were doing some work on the rear wall of the house. When they bought the house five years ago, they had it inspected by a home inspector. There is no mention of the cracks in his report. Mrs. Wilson indicated that the cracks seem to be getting wider.

Mrs. Wilson also reported that leaks recently occurred in the ceiling of the second floor bedroom at the chimney location. The Wilsons had the leak repaired. Apparently, water was entering around the chimney flashing.

PROBABLE CAUSE OF THE CRACKS

In our opinion, the cracks are caused by differential settlement of the house foundation. The right side of the house is settling more than left side. The probable cause of settlement is that the soil under the footings on the right side of the house is not as stable as the soil under the footings on the left side of the house. The right side of the house appears to be tipping downward, rotating about axes at the bases of the cracks. The leak around the chimney is probably related to the tipping settlement in that it is caused by the chimney pulling away from the roof.

We did not observe corresponding cracks on the interior side of the exterior walls. We think that the reason there are no cracks on the interior walls is that not enough movement has occurred to cause the interior building materials to develop cracks. The brick cracked because it is brittle. The interior walls have not cracked yet because the wood framing and sheetrock have more give than the brick. In our opinion, cracks will start to appear on interior walls as more settlement occurs.

A likely root cause of the differential settlement is that the footings on the right side of the house are on a fill while the rest of the footings are supported on virgin soil. Supporting a building partly on filled ground and partly on virgin soil makes it much more likely that differential settlement will occur, because it is difficult to compact fill to the same density as the virgin soil. Many builders avoid this risk by always extending the foundation walls and footings to virgin soil. Through experience, they have learned not to construct footings partly on solid ground and partly on filled ground.

CAUSES WE ELIMINATED

It is our opinion that the cracks in the brick veneer were caused by settlement of the footings. Below we list other causes that we considered, and for the reasons given below, rejected:

1. Outward movement of the tops of exterior walls due to the footings tipping can cause cracks in brick veneer walls. This rarely happens because the bearing capacity of the soil has to vary abruptly in the width of the footing. Usually when tipping does occur, it is because the soil around the outside of the footings has been scoured out by water from a faulty foundation drain. We did not observe that the exterior walls lean outward or evidence of a faulty drain.

2. Brick walls sometimes crack when they have been forced out at the top by the thrust of the roof rafters. We entered the attic and checked the hip roof framing to see if the bases of the rafters were properly tied back. We observed that adequate ties were present.

3. Occasionally we inspect houses where the brick veneer is leaning away from the wood framing because the brick veneer is not firmly attached to the stud wall with metal ties. There is no evidence that ties were left out.

4. Sometimes brick veneer walls crack because of stresses caused by thermal expansion and contraction of the wall. These kinds of cracks usually appear on long brick walls (over 50'). The cracks are usually vertical and of equal width from top to bottom. The exterior walls on your house are only about 40' long, and the cracks vary in width from ½" at the top of the wall to hairline width at the base of the wall. In addition, thermally induced cracks usually occur soon after the house is built and usually do not get worse with the passage of time.

PREDICTING SETTLEMENT

Without time-settlement data, we cannot say whether the settlement is linear, decreasing to zero, or increasing. Normally, settlement is of the decreasing type and will stop at some future date. This assumption should not be automatic, however, because of the obvious consequences if the assumption is incorrect.

The type of settlement curve can be determined in two ways: (1) by taking a series of measurements over several months, or (2) by performing soil tests. Crack gauges can be placed over the cracks to measure how fast the cracks are widening. Another way to measure the rate of settlement is take periodic elevation measurements on the walls with a surveyor’s level. A surveyor may charge $1000 for this work.

An immediate way of predicting future differential settlement is to have a Geotechnical engineering firm make soil borings around the foundation and test the soil. From the test results, the engineer can predict the rate and amount of total settlement. A soil investigation such as this may cost $2000.

1. In our opinion, it will be detrimental to the house structure if the settlement is allowed to continue much longer. The cracks are apt to double in width over the next 3-5 years. Eventually, cracks will start appearing on the inside walls. We are also concerned about the serious problems that may result from further movement of the chimney.

2. One way to stop the settlement is to underpin the perimeter footings with wider footings spaced at intervals along the perimeter. Because of the expense and risk of generating further settlement problems, we do not recommend this method of repair.

3. In our opinion, the best way to stop the settlement is to underpin the present footings with piles. With this method of repair, helical-shaped steel piers are augured into the ground next to the foundation wall. The house foundation is supported on steel brackets welded to the sides of the piers. The piers are augured into the ground until enough load-bearing capacity is obtained to support the house weight. They can be auger to depths of 30' or more if necessary. The piers usually cost about $1200-$1500 a piece. Eight or ten piers may be required to support your house foundation. If you would like, we can provide you with names of contractors who do this type of work.

Thank you for using our professional engineering services. If you have any questions concerning this report or if we can further assist you in any way, do not hesitate to call us.

Sincerely,

William A. Stanton, P.E.