Throughout the past 32 years we’ve constructed more than 6,290 foundations. When it comes to foundation design and construction, we’ve seen the good, the bad, and the ugly.
We also see many areas in new house construction that can be improved with a slight change in the construction method. These changes can have a huge impact on the constructability and performance of the building structure.
| “In this issue, we’ll talk about the best method for front porch design and construction. Builders and architects can improve their homes with this simple, but highly effective, modification.” |
The Problem
The house foundation wall that also supports the front porch is often designed and constructed in a way that is susceptible to water problems. The top of the foundation wall is
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| Water leaks caused by typical front porch construction. |
flat. The 2”x6” sill plate and the porch slab both sit on the same top of wall area.
The porch slab is often poured at the same time as the basement and garage slabs. Next, the framing is completed. Then the brick or stone façade is placed on top of the porch slab.
The problem occurs when the moisture barrier (house wrap) is not brought down from the framing and bent to lay flat on top of the porch slab. Any rain water that is behind the brick/stone goes directly to the top of the porch slab. Rain that gets onto the porch slab can find its way between the slab and brick/stone. Once that water is behind the brick/stone and on top of the porch slab, it will flow down to the sill plate, then onto the top of the concrete wall and into the basement.
Even if the original intent was for the moisture barrier to come down from the framing and then bend to lay flat on the porch slab, it doesn’t get done that way in the field. It isn’t constructed correctly. The moisture barrier starts just above the porch slab, which allows the water to get back behind the porch slab.
This is one of those areas that is very, very difficult to remedy once there is a problem. Builders have a hard time actually pinpointing where the water is coming from – and an even harder time fixing the problem.
Homeowners will usually call on particular rain days where the storms drive the rain onto the porch from the side (gable end) of the porch. The rain falls onto the porch and wind blows it back against - and under - the brick/stone façade.
It can take a lot of time, effort and headaches to fix this problem. And, your homeowner can get increasingly aggravated every time it rains and the problem isn’t solved.
The Solution
The solution is to stop hoping that the moisture barrier will get installed correctly and to create the jobsite conditions that allow it to work effectively.
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| Modified porch design eliminates water issues. |
The goal is to keep the water away from the top of the concrete wall, where it could then get into the basement.
At the top of the basement wall, create a 4” wide x 4” tall brickledge that the porch slab will rest on. The moisture barrier then extends down against the brickledge, past the top of concrete wall and sill plate. The porch slab is placed against the moisture barrier after the framing and moisture barrier have been completed.
The rain water can still get behind the brick/stone and travel down to the porch slab. And, it can still travel between the porch slab and the brick/stone. However, it will now travel past the top of the concrete wall and continue down to the inside of the porch.
Sometimes it's not a matter of how many problems like this you have with your houses, it's a matter of how difficult it can be to fix it when there is a problem. This simple design and construction change is an easy insurance policy against a water problem in this area of the house.
One Critical Item
There is one more important thing that must be done to make this system work. Be sure to continue the 4” x 4” brick/slab ledge through the areas where the porch foundation walls meet the basement foundation walls. Be sure this intersection is “notched out” to provide a break in the porch wall.
This will allow the moisture barrier to continue through this area – instead of jumping up over the porch foundation wall. If you run the porch foundation wall directly into the house foundation wall, then the moisture barrier will deposit the water on top of the house foundation wall in that area.
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| Raised porch foundation walls allow for efficient porch construction. |
Additional Tip
To reduce the height of the slab turndown at the front of the porch, raise the height of the porch wall 8”. If the basement walls are 9’-0”, then construct the porch walls at 9’-8”. This will make it easier to form the front face of the porch slab. It will also keep the formed edge straight and free from bowing.
Questions?
If you have questions or would like further explanation about this method, give us a call. Or, if you believe your construction sequence won’t allow you to construct your porch foundation this way, call us. We’ve got the answers on how to make this system work in any situation.
| "Since Herbert Construction Company has been constructing our porches with this method, we haven't had any water problems in this area." |