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Best Practices in Design-Build Residential Home Construction

When in the planning phase for a new home, it’s important to think about the constructability of the design plans. How will these plans affect construction access? Will this design require a more expensive construction method? Is there a risk of a delay in the final occupancy permit approval because construction didn’t conform to the tight design tolerances? These are all constructability questions that need to be considered during the design phase. Thinking of civil engineering plans as just a means for obtaining a permit will only cause you more problems during the construction phase of the project.

Give Room for Construction Discrepancies

We recommend giving a buffer of at least 1-ft to any building restriction setback link or at the very minimum 6 inches. Our projects in Arlington County, VA are to such tight tolerances that we trace in one line for the Foundation Wall to stakeout for construction and we draw in another 2” offset line to account for the siding of the house that will stick out past the foundation wall.

Figure 1: Site Plan view of house location on lot. (Side yard building restriction line highlighted in yellow and building setback distances highlighted in orange).

site plan

In Arlington County, VA, a final As-built Survey must be submitted to the County to be reviewed and approved for the final occupancy permit. Since the final survey must measure the main floor final trim, this can be a problem if your civil engineer doesn’t give enough of a buffer to the setback line and also doesn’t take into account the thickness of the final trim.

Figure 2: Completed home in Arlington County, VA, Green line = where final survey measures the house corners to the property line. Red line = where most engineers draft and stakeout new houses. If you tell these engineers to build your house 4” or less to the setback line, you are accepting an increased risk of occupancy permit and corrective action issues.

home in arlington county

Construction isn’t perfect; concrete forms bend, lumber isn’t perfectly straight, concrete crews don’t always follow every single brickpoint we set, framers might be off by an inch, etc. Therefore giving at least 6-12” of buffer to work with on each side of the house will give room for your construction crews to work in.

Figure 3: Example of a civil engineer not giving enough room for construction. (Highlighted in yellow = side yard setback lines, Orange = house setback distances). This engineer is just drawing in the house foundation line and is not taking into account the house siding thickness. With a 20-ft side yard setback, this engineer put one side of the house at only 0.1-ft (1-inch) to the setback line. With these plans, the foundation walls are going to be built only 1” from the side yard setback line; by the time siding and final trim are installed (adding another couple inches) this new house will be encroaching into a side yard setback line. With the other side of the house having 6.5 ft of buffer to the side yard setback line, there should be no reason to put one side of the house at only 1” to a building restriction line. This is a clear example of plans only being produced for permit and not taking into consideration the constructability aspect. When selecting a civil engineer, it is important to not choose your engineer based on lowest price or think of civil engineering plans as just a means of obtaining a permit to build. This type of thinking will result in receiving low quality plans and accepting a higher risk of construction issues.

civil engineering plans

Communication is Key

During the design process, it is important to make sure all parties (Civil Engineer, Architect, Builder, Client/Property Owner) communicate with each other. A simple miscommunication can result in costly construction mistakes and delays.

Figure 4: Another example of a Civil Engineer only giving 1” of buffer for construction to work with for installing a planter box on the side yard (Planter box and distance to property line highlighted in yellow). In Arlington County, VA, areaway steps and planter boxes cannot be built any closer than 5-ft to a property line. These Civil Engineering Plans show the proposed planter box to be built only 5.1 ft to the property line (only 1 inch of buffer). We would recommend at least 6” of buffer or put the planter box on the back side of the house instead of the narrow side yard.

installing a planter box

Figure 5: Wall Check Survey found that the planter box was built only 4.5 ft to the property line due to an added 0.8 ft thick wall along the porch addition. In figure 4 above, this 0.8 ft wall is not shown on the Civil Engineer’s Site Plan because the back wall of the planter box was designed to be shared with the porch addition wall. However, the architect misinterpreted this and drew in an extra 0.8 ft thick wall on the architectural and foundation plans which caused the planter box to encroach 6 inches into the required setback. The Civil Engineer and Architect didn’t catch or communicate this discrepancy between their differing plans. Communication or designing a 6” buffer would have saved this planter box from being built incorrectly.

Wall Check Survey

Figure 6: When it came time for construction, the concrete crews followed the foundation plan from the architect which showed the additional 0.8 ft wall that shouldn’t have been built (in red below). Now that the concrete was poured, the extra wall couldn’t be removed without compromising the structural integrity of the main addition wall. Therefore, the part of the planter box walls circled in orange had to be cut out and rebuilt. Since this planter box was for stormwater management, a revision to the approved site plan had to be submitted to rework the new dimensions of the planter box. After rebuilding the planter box, our surveyors were sent back to re-measure the planter box to confirm it was built more than 5-ft away from the property line. Arlington County reviewed the updated survey and approved the project to proceed to framing. Luckily this only happened on a planter box wall and not a main addition wall.

planter box for stormwater management

Civil Engineering Plans and Architectural Plans are much more than just drawings. These plans can have huge implications during construction. Therefore, it is important to hire a Civil Engineer that knows construction, not just the permitting process.

If you are planning to build a new addition or home in Northern Virginia or Washington, DC, please contact us for a quote on your next Land Development project.

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