Seattle - NeedsHow much house do you really need? The question is actually much harder to answer than you'd think, and not only do people come up with different answers, but the amount of space you needs typically changes with age. We adopted the exercise from the "Not So Big House" series where we paid attention to how much time we spent in each room and what activity we did there.
Our family is two people (empty nesters), and we both work mostly at home. We don't entertain very often, and when we do its usually a small informal affair. While we don't have a lot of guests, we do have a steady trickle, and some stay for a week or more. We both host meetings of various sorts off and on (Update 2010: we now rarely do this). (note: the following list was written in the old house in 2003).
From this is was easy to conclude that we needed a kitchen, informal eating space that could still accommodate a larger group or hold a meeting, a living room, a bedroom (but not a spacious one), a warm bathroom that we could both fit comfortably in and we each needed independent office space. Since some office tasks are common (like bills), we decided to expand on the "mail sorting area" idea from the Not So Big House book and turn it into a mini-office, complete with internet, since it seemed like we often used the computer together or even with other people. Added to that is storage, both for the various artifacts, old magazines, etc that we've collected, and for outdoor gear, bicycles & tools.
In shaping the public area, we considered a number of points from both the Not so Big House, and A Pattern Language. First, guests always gather in the kitchen, since just about any gathering has food of some sort involved in it. Even we gather in the kitchen, and since we were planning on a smallish kitchen, we wanted the kitchen to be well connected to the other public space, divided only an eating counter. Second, we wanted a "sunny place" somewhere in the living room.
The first indulgence was an art studio for Bob, who had been renting space fairly far away. The preliminary layout showed that fitting it would be easy- either as a dormer up in the attic or on the second floor along the north side. Although not as nice as being in a old building that is shared with other artists, the commute is certainly a lot easier, and Bob's intentions is to spend more time painting and less time working. Some day maybe there will be another website for paintings. (update 2010: alas I went back to work for a while, got involved in other things and haven't done any art since, but still hope to.)
Beyond that, our use profile didn't justify any more space, and we considered keeping it to that, but there were a number of things we felt were still missing. First, as we began doing layout, we found that the main floor was going to end up without a bathroom, which meant not only would we have to go upstairs all the time, but so would guests, something we felt was not really acceptable in our culture. A powder room is less than twenty square feet, so the space requirements are minimal, but still the idea that we were succumbing to the too many bathrooms phenomenon started to worry us.
The next issue was a guest room, since we only used ours occasionally. We considered making one of our offices also be the guest room, but the problem with that is based on our usage, we expect to both practically live in our home offices, and having to put away projects is a serious inconvenience. Justifying a separate guest room was just a matter or finding no other room that could be shared, deciding that we'd probably be having more guests in the future, and figuring that we'd also find other uses for the room. (Update 2010: since the living room area ended up very small and very central, we ended up using the guest room as a "TV" room).
The guest room led to another serious bathroom dilemma since the layout was forcing everything except the kitchen-eating-living onto the second floor (see layout). Ideally the guest room would have been on the first floor, and then the first floor bathroom would be both for our use when downstairs, for visitors, and also for overnight guests. We toyed with the idea of sharing our bathroom with guests, but in surveying a number of our friends, the consensus was that this was a really bad idea, especially since we were planning on having more guests, not less. Its not a decision that feels good environmentally (even though its just another 35 sq ft), but otherwise we're glad we decided to add it.
The final issue was whether to have a walk in closet or not, and as a couple we didn't agree. When we got to layout, we were able to shuffle rooms around and make one easily fit, and since that preserved marital happiness it also got included.
Although not a room, we did indulge ourselves on one somewhat frivolous feature: a sauna. We decided we could easily sacrifice a bathtub, since we mostly only used it to get warm after spending too much time outside (often in the rain). A sauna could be used not only in the normal way (very hot), but at lower temperatures also. This would allow us a place to get warm (at a lower energy cost than heating water), but would be a good place to stay warm after exercise and stretch.
Initially, we thought we'd need only about 1200 square feet, but like other designs we'd worked with in the past, this one kept growing. To some degree this isn't a terrible thing, since shape is equally important to size in determining both energy and material use (see also design under "how-to"). However, if you don't fight this "size creep" to some degree, you will almost certainly end up with more house than you really need.
The evolution of the basement space is an interesting examination of how size tends to creep. We had two big motivations for creating basement space: first was a place for Bob to have a workshop (update 2010: it gets used more than expected, but not as much as it could) and second was a garage. We also needed a place to store garden supplies and all the other sort of stuff people keep in garages. The city requires us to build at least one off street parking space, and since our lot is almost all much above the street, there isn't really a good ground level parking place, plus we didn't really want to park a car on the lot and we wanted covered parking (which has to meet the zoning setback requirements). All this pointed to putting the garage under the house. Still, we would only use less than half of the space of a full basement, so we got the idea to put the rainwater tanks down there also. This led to a design where the main part of the house would be on a foundation, and the two bump-outs would be on a post-and-pier system. But then later we decided that we were afraid of having the cistern in the basement, and found that preserving the existing foundation stem wall would require more concrete and expense than removing them and starting from scratch, so we now had flexibility to do anything (including floorplan!), but it was much too late in the design cycle to consider not excavating part of the basement.
This was one of those decisions that was much more about convenience and not so much about being eco. We probably could have avoided the basement if we really wanted to, but had no problem justifying it to ourselves and we believe any future owner would want the basement also. While it does seem larger than necessary, we couldn't think of an easy way to build a partial basement and have it been significantly cheaper and save concrete. Assuming that building unheated storage space can be justified, we'd argue that a basement can be a good alternative if it helps keep the footprint of the house smaller, since that leaves more space on the lot for plants and rainwater infiltration. (Update 2010: alas, the basement is incredibly full of junk, including an enormous amount of scrap wood.)
When we examine each space individually, they all seem important, and they all seem to be about the right size, with the only real indulgence in space being the third floor dormer (about 200 sq. ft), but when we imagine the completed house it seems much bigger and taller than we imagined it would be. When comparing the size to other houses that have undergone extensive remodels in the last ten years, it appears to be of comparable size, and certainly smaller than the big ones. Yet we find it hard to call it an eco-house, since it contains much space we don't absolutely need. We both grew up with siblings in smaller houses, and it never seemed to be a problem. Still, its smaller than the national average (2200 ft sq), smaller than our existing house, and certainly not a starter castle. Its just that its not really small.
Although we are not happy with how big it is, the design process still indicates that what we will get is a sensible house, and in some way, its what we'd call a dream house. The house is divided as follow (sizes are total size, including walls, not floor space):
Basement: 1060 sq ft (garage, utility closet, shop, storage)
1st floor: 1185 sq ft: 595 in the ADU and 590 in the main unit
2nd floor: 1060 sq ft
3rd floor: 192 sq ft finished + at least 400 sq ft of storage (under the roof)
When added all up, it comes to about 1875 square feet of finished space in the main unit and 595 in the ADU. The city assessor will probably count that part of the storage under the roof that you can stand in (ie 6 foot of headroom), adding about 400 sq ft to the total.
This storage area is an interesting issue: we initially considered a hip truss roof with a 5:12 pitch, which would have reduced the height of the house by about five feet. But we really liked the look of the look of a gabled roof, and also a gabled roof gave us more surface area to put solar panels on in the future (although we eliminated much of that advantage later by adding a dormer). One we settled on a gabled roof and decided on a steeper pitch (9:12), adding a dormer and the indulgence space was easy (maybe too easy!). Whether we did trusses, or a stick frame or even an SIP roof system didn't seem to make much difference in material usage, and the dormer also does use a lot of material, but admitted we didn't actually calculate the difference.
We could keep the overall height lower and still have third floor space by staying with the 5:12 hip roof and building a cupola in the center of it. In fact a remodel is almost finished a block away that did exactly that, and in their case it does look very nice. Its not likely that it would have any impact on either materials, energy or cost though, and so other than the emotional issue of feeling like the house is too tall, and the fact that it changes the look of the house totally, there isn't any difference.
Adding an Apartment
People add apartments to their homes for a variety of reasons, often for additional income, and environmentally the benefit is the same as any multi-family housing: less material is used, and there is better energy efficiency and higher density land use. Our desire was purely selfish: we wanted someone there to take care of the house so we could be away for long periods of time. Because building the additional space takes resources, we felt it was important to make sure that this was a sensible choice. Many times we considered dropping the idea, saving ourselves additional expense, but always came back to including it. Once we considered the flexible living arrangements that could be done with it, including the possibility that some day we would downsize again and live in it, we were sold on the idea. Although the apartment complicated our design process greatly, we don’t believe it impacted our ability to follow our own design criteria, it was just that we would be building two living units, not one.
The city of Seattle allows "Accessory Dwelling Units" or ADUs, sometimes called mother-in-law apartments, as long as they are part of the residence (not detached), have a entrance that does not face the main street, and not be greater than 1000 square feet. This zoning rule, distinguishing this type of apartment from a duplex or triplex, is a political compromise between those who favor greater density, and those who want to maintain the single family characteristic of many Seattle neighborhoods. Since these criteria were well within our desires, there is no code impediment to having an apartment.