Second Story Additions: What to Consider Before You Get Started

Whether you’re looking to add a master suite, a bonus room, or a combination of several spaces to your home, a second story addition can be the perfect solution. Here’s a look at some key things to think about when considering a second story addition, along with a breakdown of average costs and timelines.

Second story additions are a great way to add space and value to your home. But everything from the age of your home to the type of addition you want to do can affect both the budget and the timeline. So where do you start? First, let’s look at when a second story addition may be right for you.

When does a second story make sense?

A couple of common reasons can influence whether you do a second story addition rather adding on to your home horizontally.

Lot size

Lot size often plays a role in determining whether to do a second story addition. If you have a narrow lot, you simply may not have the space to build out, so you need to build up.

Preserve existing landscaping or yard space

Another common reason for doing a second story addition has to do with saving the existing yard space. Maybe you want to add a deck or a pool at some point. Or you really like the landscaping. Either way, you’d like to keep the yard space you have so you don’t want to expand your home’s current footprint.

Key considerations to adding a second story to your home

So what should you look at in your home to determine how feasible a second story addition may be?

City restrictions

A good place to start is by investigation general city planning requirements. Call your city planning office and see if there any height restrictions that may apply to your addition. You can also drive around your neighborhood and look at some of the other houses. If they have additions similar to the one you’re thinking about, chances are you’ll be allowed to build yours as well.

Engineering requirements

Next, you’ll want to consider your home’s age and its engineering, specifically its gravity loads and its lateral loads. The gravity load is the level of pressure being exerted from the top of the home down to the foundation and below. Lateral loads are forces like strong winds or earthquakes that exert pressure on the sides of your home. If these are strong enough and your home is not adequately reinforced, it could topple in on itself or collapse.

Some of the pre-1940s homes in the Portland area (where Lamont Bros. is located) do not have proper footings or any footings at all. That can make adding a second story addition challenging as the gravity load can become too great. Post 1940s homes usually have footings, but in many cases we’re still reinforcing them by placing an additional footing to help balance the load throughout the house.

Older homes can also pose a challenge when it comes to lateral load. Many of them don’t have sheathing or shear walls (usually plywood walls to counteract lateral forces) under the siding. So often, we need to remove all of the siding from older homes and install shear walls before we can build the second story.

Most newer homes will have shear walls already, but we may add some in certain areas in order to safely construct the second story.

Types of second story additions

Second story additions comes in 3 main types.


second story addition: dormer

With dormer additions, we leave the existing roof line, take a section of it, and extend it from the roof line either with a gable dormer, a shed roof dormer, or another style. The advantage of a dormer is that the engineering process is usually easier, since the scale of the addition is smaller. The disadvantage is that a dormer doesn’t provide as much new space as other types of additions.

Partial second story addition

second story addition: partial addition

In this type of addition, we remove part of the roof, add a second story, install a new roof on top if it, then tie everything together. A partial second story addition makes sense when you want to add a moderate amount of space like a bedroom or two or a bonus room and you aren’t looking to double the size of the home.

Full second story addition

second story addition: full addition

If you need to add a lot of space to your home, the best option may be a full second story addition. This involves removing the entire roof, building a new story on top, and connecting the new spaces with the existing structure of the home. These can be ideal if you want to add a master suite and other bedrooms, then redo the main floor with an expanded kitchen remodel or renovated living spaces. Often, first floor remodels will be folded into second story addition projects because when you’re adding so much square footage to the home, clients usually want to change the floor plan of the main level.

Second story addition costs

Costs for these types of additions can vary widely depending on size and complexity. For planning purposes, here are some average ranges.

Dormer costs

A dormer second story addition typically ranges from about $90,000 to $230,000 in the Portland metro area.

Partial second story addition costs

A partial second story addition can range from about $290,000 to $465,000. A lot of it depends on what’s going inside the addition. Is there a bathroom or not? Is there a master bathroom or a standard one? How big is the addition overall?

Full second story addition costs

A full second story addition will be the most expensive. Usually, these start at around $465,000 and go up. This has to do with the extent of work involved and the engineering that takes place, as well as the elements going in to the new spaces. As a general rule, these types of additions will cost more than expanding out on your home.

How long does a second story addition take to build?

As you can imagine, the complexity of your project will affect the timeline. When working with a design/build firm like Lamont Bros., the design phase of the project generally takes 3-5 months. These types of projects involve significant design work, as well as engineering-related investigation. The more investigation that needs to occur, the longer your design phase may take.

Next, the permit phase. This can range anywhere from 1-6 months depending on the jurisdiction and whether the company you’re working with belongs to something like Portland’s FIR program, which can fast track the permitting process.

The construction process itself will usually last about 5-9 months, depending on the scale of the remodel.