***amended for 2023 figures, most builders of full home projects tend to charge around $400 per square foot for entry level construction quality and $600 and up for high end quality. Smaller projects tend to have less economy of scale and can cost more.***
In my practice, we design about 100 residential projects per year, and when it’s time to get the project built, we usually reach out to several builders for construction estimates before we finalize the drawings, get structural engineering, and get building permits. This enables us to get a ballpark sense of what the project might cost to build before spending too much time (client’s money) on the details. In doing so, we often get a range of pricing back from builders, but no matter how many times we advise on what we think it’s going to cost, clients often do not want to believe it (they often think their situation is simpler than everyone else).
We get no financial incentive on the cost of construction as architects. We just design the house per the clients’ requests, advise them on decisions, and create drawings and documents to communicate the goals to the builder. Complexity is mainly what affects cost. Complexity comes in two ways: design complexity and construction complexity. When a client is on a budget, we design a very straightforward solution, so a builder can do simple, repetitive work using inexpensive, familiar materials (a rectangle with painted siding, shingles, carpet, and drywall).
Despite the simplicity of design, the complexity might be more related to the property itself. Is the property on a steep slope? When you dig, can the dirt be dispersed on site, or do you need to pay to truck it elsewhere? Can a concrete truck drive right next to the area of work, or is a big pump truck necessary? Is there anywhere for the builders to park, or will they need to cart tools and materials long distances every day? Is there a place for delivery trucks to easily drop lumber and other materials, or does a crew need to carefully coordinate the material delivery with a crew of laborers to quickly get the truck unloaded and material sorted and stacked while the delivery truck is holding up traffic? Is there space inside and outside the house for builders to spread out materials? Is there complicated demolition that requires parts of the existing house to be temporarily supported during construction? Is the soil mushy and require really deep concrete footings or steel pilings? Is the new addition above an existing part of the house that must be retrofitted and largely rebuilt to meet current codes for structural requirements, energy performance, redoing the whole roof, redoing all the siding, plumbing upgrades, and electrical upgrades?
There is so much that goes into a home addition that affects the cost of construction if you are not building on a simple, large, flat property with an existing house that was not recently/properly built. If any of the factors listed above are involved, it could easily double or triple the cost of typical construction. Projects in the Seattle area almost always have many of those factors, so the construction cost in Seattle is “through the roof.” The size of small projects doesn’t really have that much of an impact on the construction cost. Small projects carry all of the same steps and burdens as large projects, so they end up being really expensive. For example, if you need to update your electrical panel on a total house rebuild or on a small 1-room addition, the cost is the same on each project example to update the electrical panel regardless of the size of the project. There are many scenarios like this in construction where size plays a minor role in cost, and a big project might be marginally different from a small project. The diagrams below outline an example of a simple and a complicated project, and they illustrate the common construction cost estimates we typically see from builders.
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Easy project
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Hard project