Using Cracks in Gypsum Board to Assess Foundation Movement
Hello everyone – I hope you have been doing well. I know I’ve been away awhile but I plan on doing more these blog post again. The truth is that I got away from it because I wanted to rethink my blog goals, topics, and general post structure and scope. I’ve decided that I would like to refocus my blog on topics I deal with as a forensic engineer, and keep the blog posts simple and focused on a specific topic. We’ll see how this new blog structure works out in the next month – feel free to leave some comments on how you like it.
With that update out of the way, I would like to jump into our topic for today – gypsum board cracks in a house and how it relates to foundation movement. A fair number of the house inspections I do involve assessing these conditions and determining if there is a correlation to any possible foundation movement.
In my experience, cracks in the gypsum board finishes of a house fall under two categories – tapered cracks, and expansion/contraction cracks at gypsum board joints.
Expansion/contraction cracks are visible in most houses – most commonly in the garage due to increased outside exposure along with the relatively less insulated and/or finished conditions. However, these cracks can occur in other areas of the house as well. These cracks will typically be horizontal or perpendicular in orientation, have an even gap across the length, and be patterned at typical lengths/spaces of gypsum board joints or at wall-to-ceiling and wall-corner joints. These cracks are not directly correlated to foundation movement in most cases and are instead the result of the expansion and/or contraction of the gypsum board.
Tapered cracks, usually at doors, windows, and ceiling and wall joints, are visible in most houses as well. These cracks typically extend diagonally at susceptible areas when not at wall or ceiling joints and are indicative of some form of foundation movement. It is more common to see these tapered cracks in houses with a concrete slab foundation due to the foundation resting directly on ground which makes them susceptible to seasonal fluctuations of supporting soil. However, these cracks can be present in any house depending on their construction and conditions of the surrounding lot.
When discerning the cause of the gypsum board cracks, these inspections also require the correlation of the location and relative age of the cracks to measured low spots or high spots. When my company performs these foundation inspections, we use a compulevel to determine relative differential movement of the foundation. If a crack is located away from a high spot or low spot, it typically indicates that it is either expanson/contraction related or the result of foundation movement that has occurred previously and has since leveled again. In addition, if paint or significant amounts of dust/debris are present in the cracks, it usually indicates that the crack has been present for a relatively longer period of time (depending on when the interior finishes were last painted). Using the above information, we can determine which cracks are the result of relative foundation movement and how long the possible foundation movement has been occurring.
While most of you probably don’t have access to the equipment to find a relative floor elevations and measure differential movement, this information should help when initially assessing the cause of gypsum board cracks, and also help in understanding the foundation inspection process. I will probably write a few more blog posts covering the basics of foundation inspection, so feel free to ask me any questions you have and I will answer them if I can. I would also like to hear from people in the inspection business as well. For those with inspection experience, how do you assess gypsum board cracks in relation to foundation movement? If you enjoyed my post, hit the like button, follow my blog for updates and share this post with your friends. Thanks for reading and have a good week!