Building a new house in Arlington County, Virginia can be one of the more difficult areas to build in the Northern Virginia region. Trying to maximize your lot coverage on a typical Arlington lot can be extremely challenging due to a number of constraints such as lot setbacks, maximum lot coverage allowed by zoning codes, tree preservation, and stormwater management requirements.
One of the first steps in the process is selecting the house footprint size you want and fitting that footprint within your lot setbacks. After we finish our Topographic Survey, and we receive the Architectural files from your Architect or Builder, we will work on the initial Site Layout.
Below is an example of a preliminary lot layout fit within the setbacks on an Arlington lot. This typical 60-ft wide x 100-ft deep lot in a R-6 District has a Front Yard and Rear Yard Setback of 25-ft each. Then one Side Yard Setback needs to be 10-ft and the other 8-ft. That leaves the buildable area envelope of 42-ft x 50 ft, with a maximum house dimension of 41-ft x 47-ft that will barely fit within those dimensions.
During this preliminary Site Layout phase, we will take the Architectural files given to us and trace in the building footprint on our Site Plan with the Existing Conditions from the Topographic Survey shown in the background. Once we trace in the building footprint, our Civil Engineers will evaluate how the proposed building footprint fits within your lot setbacks and provide feedback. We evaluate for compliance with the Arlington County Residential Setback requirements.
With typical lot sizes in Arlington being around 60-ft x 100-ft, fitting a new 41-ft wide x 47-ft deep house can be a challenge. We have to factor in every inch including the thickness of siding and final trim that sticks out beyond the foundation walls. If your Civil Engineer doesn’t factor in the thickness of siding, and just draws in the foundation walls on the permit drawings, it can cause problems at the end of the project when you are ready to receive the final occupancy permit to move in. We generally like to design a house to be at least 6-12” away from any building setbacks to account for final trim, any deviations during construction from the concrete and framing crews, as well as other factors of error that may come into play.
During the initial house footprint sizing, there will be a few iterations of design where we work with your Architect to adjust the footprint slightly to better fit within the setbacks. Other design adjustments such as sizing and locations of basement steps, bay window projections, and chimneys, will need to be decided upon at this time.
Not only do we need to comply with building setbacks from the property lines on all sides, but we also need to comply with lot coverage maximum areas allowed by zoning. Even if a house fits within the building setback envelope, we still need to comply with the maximum building and lot coverage areas. When determining lot coverage, each zone is different depending on where your property is located in Arlington County, and will need to be calculated by our Professional Civil Engineers based on a number of factors.
Depending on which Zoning District in Arlington your property is in, the main building Footprint Cap for a house with a porch 60 Square Feet or greater, is as follows in the table below:
|District||Main Building Footprint Cap w/ Front Porch||or|
% of Lot Size
|Typical Lot Size||% of Typical Lot Size||Total Floor Area (Bsmt, Main + 2nd)|
|R-5||2,590 SF||37%||5,000 SF||1,850 SF||5,550 SF|
|R-6||2,772 SF||33%||6,000 SF||1,980 SF||5,940 SF|
|R-8||3,136 SF||28%||8,000 SF||2,240 SF||6,720 SF|
|R-10||3,920 SF||28%||10,000 SF||2,800 SF||8,400 SF|
|R-20||5,320 SF||19%||20,000 SF||3,800 SF||11,400 SF|
If your front porch will be less than 60 SF, then the main building footprint cap will be a few hundred square feet less or 3% less of the lot size. It’s important to note that the main building cap is the lesser of the main cap number or percent of your lot size. Therefore, if the main building footprint cap is 2,772 SF for your building lot in an R-6 District, but your lot size is 6,000 SF (60-ft wide x 100-ft deep), then the main building cap is 1,980 SF (33% of your lot size). The only way to increase that size is to have a bigger lot than the average 6,000 SF lot in that district. Say for instance, you have an 8,000 SF lot in an R-6 District, your main building cap will be 8,000 SF*33%= 2,640 SF. However, if you have a 9,000 SF lot*33%= 2,970 SF, that doesn’t mean you can build up to 2,970 SF. In that case, you would be limited by the Main Building Cap number of 2,772 SF. It’s the lesser of the Cap number or Percent of the lot. Our Civil Engineers will calculate these numbers for you once you select a lot to build on.
We generally advise to keep the maximum building coverage at least 100 Square Feet under the maximum allowed by zoning code. Designing a house to be built too closely to the maximum allowed limit increases the risk of building over the limit. If a house is built over the maximum building coverage, it will result in delays of obtaining your occupancy permit and possibly may include corrective actions requiring you to rebuild a portion of your home. Imagine completing the construction on a $1-2M home and not being able to move in!
We cannot stress enough how important it is that you do not push the limits! At the end of every project, our Land Surveyors have to survey and as-built certify the final dimensions of your completed home. Not only do we need to certify that your house meets the setback requirements and height requirements, but also with the final lot coverage area. The same Arlington County Zoning Office that issues your Final Occupancy Permit needs to review the Final Survey Plat before they issue your permit to move in.
This is why during the initial site layout design phase, our Civil Engineers may advise you to adjust the size of your Architectural drawings before proceeding further into the next phase of design.
We Design for Construction, not just Permits
Construction has improved greatly over the years, but it’s not perfect and we have to design to give construction crews a reasonable buffer of error to work with. If you do not give construction this room to work with and tell your Civil Engineer to design to the absolute limit, you will be setting your project up for failure. Concrete forms can bend and be set up an inch off, framing crews could be off an inch, your civil engineer might not factor in the 2-3 inches of siding and trim beyond the foundation walls, your property lines could have a 1-2 inch discrepancy. All of these factors can easily add up to 4-6 inches of error during construction, which if designing too closely to the limit, could cause your house to encroach into a setback line or beyond the building coverage limit.
Remember to plan ahead as much as possible, the planning process is something you want to be efficient with but not rush in haste nor push the limits. Civil Engineering Plans are more than just a means to obtain your construction permits; they are also construction drawings that can make or break your project. By the time Civil Engineering Plans are released for construction, it may be too late to make any changes.
Our Civil Engineers are experienced with the realities of construction and will help consult you every step of the design process to project completion so that you have a successful and stress free experience.
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.