Trained Eye

 
 
 

House Shifting & Underpinning

Question:

I would appreciate your advice on the following.  I have a 25-year-old bungalow that has experienced some shifting on both sides of the house. This has caused a number of visible cracks throughout the house.  I have had 4 estimates, which all are recommending putting piles around the perimeter of the house.  In your opinion, is this the recommended solution?  This is not a minor repair and I was wondering if there is some other method of determining the right course of action. Will this procedure prevent any further shifting? My concern is that neighbours on either side have not had any shifting problems.

Answer:

With the extremely dry spring and summer weather we experienced this year, I have been receiving an unusually large number of calls and e-mails about house movement. As the expansive clay soil in the Red River valley has dried out after several rather wet years it will shrink considerably and cause even more shifting in homes than normal. I will answer your question and give my opinion, but it is difficult to accurately judge the depth of the problem from your limited information.

This question is timely for me, as I inspected a home that was of similar age this week with an unusually high amount of settlement to one side of the home. It was quite noticeable, both from the street and inside, and the floor slope was very apparent. The unusual part was that the home was a corner lot, adjacent to a fairly busy street, but the home was settling away from that street. It is typical to have settlement toward a busy thoroughfare, due to vibration from heavy vehicle traffic. Unlike your home, however, there were few cracks in the walls and other signs of settlement, other than the sloped floors and doors that swung open on their own.

My reason for bringing up this personal experience is to help illustrate the point that house settlement is not a cut and dried phenomenon and will vary from home to home. There is often no visible cause of the unusual movement and no firm repair method. Even a seasoned veteran like myself who inspects hundreds of homes every year will see odd situations, like the one illustrated, that defy convention. With this point in mind, I will recommend you get as many professional opinions and viewpoints as possible before spending thousands of dollars on remediation. As far as I’m concerned, underpinning foundations should be the repair of last resort for house settlement. It may often be warranted, but is very costly, invasive, and can cause further issues if not done properly and completely.

Underpinning repairs on existing home foundations consists of drilling deep, large diameter holes in the ground under the footings and pouring reinforced concrete piers, commonly referred to as piles, in to these holes. These piers should go deep below the area where frost will affect their movement and prevent further settlement or dropping of the heavy house foundation. In the past, many foundation contractors would partially underpin homes, installing piers under one or two foundation walls. This is not done nearly as often, today, with good reason. The partial underpinning method would support the walls on the low sides of the home, in the direction of movement, to help prevent further settlement in those areas. This often caused uneven movement and settlement as the non-supported walls continue to move. Further problems can develop in this scenario, making the concerns greater, rather than solving the initial movement related issues. If underpinning is attempted it should be the entire perimeter foundation, and sometimes the footings under the centre of the house, that should be done to prevent uneven, differential settlement.

Too often cracks in interior walls of a home can mistakenly be attributed to foundation problems, when that is not the true problem. The footings under the teleposts and main beams in the home are subject to differential settlement from the perimeter foundation. We won’t go into the reasons for this extremely common phenomenon here, but anyone who has owned a new home not built on piles has experienced this issue. If the teleposts have not been regularly adjusted throughout the quarter century of your home’s existence, they will likely be pushing upward on the floor in the centre of the home creating many cracks in the walls. This will be compounded if basement walls were built with no allowance for basement slab movement, or slip joints. These walls can also push up on the floor joists, creating uneven floor heaving and cracks in the drywall.

You have gone down the right path by consulting foundation contractors for possible solutions and prices to solve your problem, but you must keep in mind that these people have a stake in selling you the repairs, whether they are completely necessary or not. Evaluation by a licensed Structural Engineer or CAHPI home inspector, with direct experience in residential foundation inspection, should be your next step. This will get you an independent, professional viewpoint, without the sell job. It may be necessary to remove some of the insulation and wall coverings from the interior of the foundation, if present, before this inspection to allow for a proper look at the problem.

 

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