Doug’s Note: If you’ve ever had a problem with your
basement foundation, then you know how frustrating and expensive that can
be. Throughout the year, we publish
Technical Bulletins that inform and educate Homebuilders, Architects, Engineers
and homeowners on ways to reduce foundation problems and improve their basement
construction design. Here’s #13 –
Alternative Foundation Detail
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Figure 1: This detail shows the typical method of placing
the floor system on top of the basement wall.
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Typical
Floor System
The typical home building method of placing the wood
floor system on top of the concrete basement wall has been used for
decades. The height of the flooring
system naturally requires multiple steps from the Main Level down to the finish
grade. Figure 1
shows this typical detail.
However, there are certain situations where the typical,
multiple steps into the house would interfere with the design of the home. Lifestyle preferences, accessibility issues,
and rainwater management may require that the distance from the Main Level to
the finish grade is one step or less.
This Technical Bulletin will show how to accomplish that.
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Figure 2: This detail shows an alternative way to construct
the foundation, which allows the finish grade to be raised
nearer to the Main Level elevation.
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Foundation
Modification
To allow the finish grade to be brought up near the Main
Level, the top of the foundation wall is raised. Figure 2 explains this alternative detail.
The foundation wall is elevated to 1 ½” from the bottom of the
subfloor. The treated sill plate is
placed on top of the concrete wall, and the subfloor extends over the sill
plate. By raising the top of foundation
wall, it raises the allowable height of the finish grade. The floor joist/truss is then placed on the
inside of the foundation wall and is supported by a stud wall placed ½” away
from the foundation wall. See Figure 3 for more information on this foundation
detail.
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Figure 3: A detailed look at how the components
work together in this alternative foundation detail.
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This specific method of construction is referred to
within our company as the “Bildon” detail.
We’ve named it that because one of our good clients, Rick Fierer of
Bildon Construction, always builds his homes with this configuration.
Another client, David Weekley Homes, utilizes this detail
on the front of their basement foundations to manage rainwater issues and to
reduce the number of steps leading to their front porches.
Practical
Applications
There are many applications for this foundation
detail. Here are a few examples:
Active Adult / Barrier-Free Entry: Homes designed for the Active Adult market or those that require
barrier-free entry into the home do not have multiple steps into the Main Level
from the front porch, garage, or rear patio.
We use this foundation detail on many of those homes because it reduces
the distance from the Main Level to finish grade or a concrete slab.
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Figure 4: The foundation detail was use on this
Marietta home, allowing the finish grade to be
raised between the garage and front door, preventing
water management problems.
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Courtyard Floor Plans: The area in the front of the home
between the front door and a courtyard entry garage is always a tough area for
rainwater management. The driveway and
front porch naturally trap water in the area near that corner of the
house. This foundation detail allows the
grade to be raised in this area, which lets rainwater drain across the
driveway. Figure 4
shows an example of how we used this detail to prevent
potential water problems on a courtyard home in Marietta for Kyle V. Henry,
Inc.
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Figure 5: This side entry garage plan shows the area
of concern where rainwater can congregate and cause
a leaky basement. The basement wall can be raised
in this area, minimizing water problems.
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Side Entry Garage Plans: Side entry garage plans can pose a
water management problem. The farther
the front porch is from the garage, the worse the problem becomes. This is because the area that catches
rainwater is enlarged, and it has to be directed away from the foundation.
See Figure 5 for an example of this. Whenever
water is detained in an area next to a foundation wall, the potential for water
leaks into the basement is multiplied.
To reduce this problem, the finish grade has to slope away from the
foundation to prevent rainwater from standing in this area. When this foundation detail is used in this
area, the finish grade can be raised near the house, allowing rainwater to
drain away from the foundation.
Minimal Step for Pool Area: Some homeowners want a pool to be
close to the rear of their home. They
want this outdoor living area to be an integral part of the home experience. They view multiple steps from the Main Level
down to the outdoor area as a barrier to enjoying that space. This foundation detail minimizes the step
down to the outdoor area, which allows it to be a more enjoyable feature of the
home.
As you can see, there are many practical applications for
this foundation detail. Our goal for our
Technical Bulletins is to share with you the tools and techniques that we’ve
utilized over the years of building concrete foundations. If you are aware of these best practices for
foundation construction, you may find the perfect application on an upcoming
project and save yourself a lot of time and money.
If you have any questions about this foundation detail,
or how to apply it on your projects, you may contact our office at
770-795-0103.
