Before you begin the work to decide if an addition is right for your property, the first step is to determine your ‘why.’ Why do you think you need an addition outside of the current footprint? Is an addition the best solution to solve your problem? It’s important to work with a builder who will help you determine if an addition is the best route for you and your property as there may be other ways to gain more room using the existing footprint.
As you begin dreaming up a home renovation project, it is important to first know how much money you are willing to invest in your project. The budget often dictates which addition route to go: up, down, or out. While adding a basement may seem appealing, it likely means jacking up the house and digging out the new space. It might be more cost-effective to build a space in the backyard or expand the attic. Generally, adding onto a house at ground level is the least expensive option. Adding a second story, or digging out a basement tends to be more expensive because the city of Seattle requires renovated homes to be completely updated to code. Suddenly, the renovation would also include paying for the cost of the addition, and the cost of bringing the rest of your home up to code. This can get expensive. If you are adding onto the existing house at ground level, you don’t always have to bring the whole house up to current code like you would with adding a second story, or basement.
Pros & Cons of the 3 Different Options
Up (second or third story additions)
Pro: The biggest pro of this addition style is that you don’t lose any valuable yard space.
Con: You may have to update the rest of your house to support the new second or third story. You also have to give some space up in the existing home to make room for a staircase connecting the main floor to the new level.
Down (add a basement)
Pro: Basements aren’t calculated in the floor area ratio calculation (FAR) which means it will essentially be ‘free square footage.’ If you have already maxed out the FAR calculation, then you can still build down because square footage below grade isn’t factored into lot coverage regulations.
Con: This is often the most expensive route to an addition because it includes jacking up the house, digging out space in tight quarters, and pouring a new foundation in some situations.
Out (ground level addition)
Pro: This is typically the least expensive and ‘easiest’ addition to do of the three options.
Con: Building out can take away from yard space and can also include more constraints caused by setbacks and lot coverage requirements.
Lot Topography Restraints & Access
The lot topography will significantly impact what style of addition is even possible on your specific property. Some lot styles are more challenging than others:
Steep slopes pose the most significant challenge because they make for the most expensive foundations. Building anything on this style of lot will require extensive structural engineering work.
In high-density urban areas like Seattle, homes without alley access can create challenges for excavation and general property access like mobilizing deliveries and equipment.
All environmentally critical areas (ECA) restrict the buildability of the lot and points of access.
Height restrictions within the area of the home can be a challenge for adding 2nd or 3rd story additions; power lines can also pose an issue. Read SDCI Tip 220 for more information.
Setbacks: building forward (into the front yard) usually means there's the least amount of room to work with due to property setback rules. But sometimes forward is the only route to go, like if the home is setback further than neighbors with a large front yard. Homes with minimum setbacks on the sides may end up having to spend more money to create an access route to the back of the lot for equipment and deliveries. For example, if your neighbor has a fence up and your home is close to the property line, you may have to negotiate with the neighbor to take down part of the fence or plan an alternate access route.
So, how do you get started? Choosing the right building team who will advise you on the best route to take based on your budget, topography, lot size, and shape is the first step. The best solution for your budget and needs should be obvious to a high-quality building team who has experience.