In my last blog I discussed how aerial photography helps us better understand site conditions. Somewhat related to aerial photography, is understanding the topography of the area surrounding the house. Below I’ll cover the basics of using site topography in foundation assessments.

Using Site Topography in Foundation Assessments Can Uncover Issues

When assessing the water on a site, knowing how it originally drained and how it drains now is important. Much of this, but not all, can be better understood with aerial photography. The remainder of the information you’ll need can be gathered by using site topography in foundation assessments. 

This additional tool is important in many ways. For instance, if the site is currently sloped it will need to be leveled before a house is built there. Also, understanding where areas have been filled might help explain some settlement. This is because settlement can occur even after a properly compacted fill. 

Or, conversely, if a cut was used to level the site, those areas might typically display more propensity for heave. Of course, these are not ironclad rules. I have seen fill sites overly compacted with clay, which can cause heave. I have also seen cut sites that are over excavated and improperly filled. This resulted in settlement. However, these are less likely than the above mentioned observations. See diagram below.

Note: When factoring in site typography in foundation assessments even Google Earth has tools you can use. It displays the corresponding elevations of an area as you hover the cursor, helping show the variation in slope.

Don’t Forget to Consider Size  

Just as much as slope, the size of the site is an important factor for understanding how water drains on it. When using site topography in foundation assessments it’s important to note the site size. Some sites have more space surrounding the home than others. This space can be used to facilitate distributing the water away from the house. Or conversely, it can exacerbate poor drainage problems and shed more water towards the house. 

For example, if there is an upward slope near the house and it is a fairly large area, it can drain a lot of water towards the back side of the house. Depending on conditions, and how water is distributed near the home, it may affect the performance of the house in different areas. 

 Using Site Topography in Foundation Assessments Can Also Provide Solutions

As mentioned, although the slope found on a site can help determine where the problems lie, the size of the site and areas around the house need to be factored in a well. Factoring in site size can help formulate a proper drainage plan. For instance, if there’s a lot of room, properly grading the surface to shed water away from the house is one cost effective solution.

Other fixes can aid surface drainage too. Things such as retaining walls, soil blows, and drainage ditches can remedy the issue in a large area. If on the other hand, there is very little room, and the drainage and slopes are slight then there are other options. These options include using gutters and hard piping to drain moisture to at least twenty feet away from the house. 

By using site topography in foundation assessments you arm yourself with another tool for both finding problems and creating needed solutions. You can read more about the foundation inspection process and all of the tools available for getting accurate assessments on my blog. You can also sign up for my newsletter there, to get my latest blogs delivered directly to your inbox.