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What’s really up with a 2nd floor addition

by Steve McKee on July 11, 2004

I met with a homeowner last year who was in the early phases of her thinking about where to add a master bedroom addition to her one story house. Should she go up or sideways? Which was the cheaper square footage to add? She had met with a couple different builders and had not received a black and white answer and was frustrated that no one could give her a simple response. Truth is, there is no simple answer to this question, but the one thing I knew with some certainty was that the next builder or designer to come along with this homeowner and make a strong case for either outcome (and then top it off by acting completely certain about his answer) would have her undying allegiance.

I was unwilling to take advantage of this situation and told her what I knew about the many aspects that should influence this decision. A lot of it has to do with how difficult it will be to make the foundation strong enough for the added loads. Another big aspect is whether the existing roof framing can be easily remodeled to receive the new upstairs floor framing.

The various reasons people may have for adding a second floor to a one story house are pretty easy to understand: to add to the house without taking away yard space; to get a good view you wouldn’t otherwise enjoy; to give a new look to what may be an undistinguished house. Homeowners’ instincts about considering the value of these things are usually pretty good, especially if they’ve lived in the house for any length of time. Then there are the hidden factors involved with the upstairs addition that are not so easily known. Things like expense, structural issues, living through the remodel, and what about the stairs?

Remember these good reasons (save yard, get view, add distinctive look or curb appeal) because you’re about to read why it’s usually more expensive to go up with an addition rather than sideways. Given the high dollar value of houses these days, I think it’s not smart to save a relatively small amount of money if it diminishes the livability and value of an asset as important as your home.

Regarding expense, if all factors are equal, adding square feet by adding a second floor is usually more expensive than adding the same square feet with an addition at ground level. The second floor addition will require fussy carpentry to fit the new framing to the existing framing, more so than a one story addition would. This includes removing roof framing in a manner that keeps the lower ceiling intact (or involves removing the lower ceiling and expanding the remodel work into the lower room as a result.) Are there gas lines or heating ducts that need to be relocated? There’s more extensive earthquake reinforcing to do, because two story houses have much more sideways force acting on them during a quake than a one story does. And this seismic reinforcing work will often invade first floor rooms that you may have thought were out of the way of the remodel work. There’s also the added difficulty carpenters experience while attaching siding and trim while ten or twelve feet off the ground with scaffolding and often two carpenters needed for a given chore, with a ground based cutter and a ladder based nailer. And so it goes, all these extra costs adding up.

The stairs that are now needed also add expense and take up space, requiring more space to net the same usable square footage. If you carpet the stair and keep the railing simple, you can hold expense down. That said, we agree, don’t we, that a nice stair is not such a bad place to spend a little money? A well done railing can add a nice highlight to a house, and give a focal point amidst all those plain sheet rock walls. A stairwell can also make a very nice “light well” where the resulting slot of 2-story space can be used to bring daylight into the heart of the house. This is good stuff.

With a second story addition, there are some nominal savings in some categories, like roofing, because we’re reducing the total roof area. We’re not adding as much foundation either, but the foundation work is usually more labor intensive. One story houses have foundations that are almost never ready to receive an additional floor of load. What to do? Well, you’ll be glad to know that there’s a variety of tactics that can be brought to bear. You never have to fully replace the existing foundation just to add the second floor (unless, of course, it was a failing foundation that was in need of replacement anyway.) Usually you can just reinforce selected spots on the foundation where the new loads from the second floor are concentrated. This often consists of digging out under a small section of the foundation and adding concrete and rebar to create a new wider and stronger footing in that spot.

Here’s some good news for owners of Southampton houses with concrete slab foundations: in most cases the extra thick “matt” slab foundation used in the Southampton houses can handle a second floor of load if your second floor framing is done creatively with loads dispersed over many different points and not concentrated too intensively in any one spot.

Staying in your house during the construction work is usually easier with a one story addition, unless of course the addition involves huge remodeling of other areas of the house. It’s easiest to live through such an addition because the new work is located outside the existing house, at least for the first month or so. All the work on the foundation, framing and siding can happen without having to break through the existing envelope of your house. It’s sort of like the project is not in your home but rather in your backyard or side yard. You’ll surely have to connect the spaces when it’s time to sheet rock. After that it’s plywood and visqueen separating you from the dust, noise and job site radios tuned to stations with names like “da bone.” (Maybe that last one can be negotiated away.)

There’s a whole lot more that could be said on the subject of the second story add-on, like where to place the addition to best blend it in with the original house (to make it look like it was always meant to be there, in other words.) Books could be written on that subject, that’s for sure. Maybe we can take that one up another day.

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