Building Layout
With you needs and desires outlined, the land chosen, and the site on the lot also chosen, you can now start shaping the building. This shaping is a tug between the needs of individual rooms, and the need to assemble them, like pieces of a puzzle, to all fit into a single envelope.1
Some of these patterns might read as being a bit judgmental, but the intent is to stick to the "if you do this, you get this" model.
5) Bubble diagram
Make an initial placement of each room by drawing a "bubble diagram".
Draw each room as a circle with its name on it, and place it in its preferred
compass direction (eg SE, north, anywhere), while also placing other rooms next
to it that are directly connected to it. This exercise shows the
relationship of the rooms to each other and the orientation of each room to the
site.
There will typically be conflicts at this stage: two rooms want the same location, or maybe two rooms want to be adjacent, but want orientations that don't allow that. Tradeoffs will have to be made at this point, until every room is place, connected to which rooms it needs to be connected to and oriented on the site the way it wants to be.
As a general rule public spaces face the sun (south) because they are the spaces occupied during the day and so demand both light and heat, while private, especially bedroom require less heat and light, but want more are more noise sensitive. Keep in mind that this isn't always the case, and that sometimes a northern exposure may be preferable, like for an art studio, reading room or home office. By nature, buildings have variations of light, with some being bright and others more softly lit, so match the light need with the location in the building. Luckily, spaces requiring the most privacy usually are also better with soft light.
6) Just the Right
Size
A house is just the right size when every attempt to make it smaller
results in a serious impact on its usability or build-ability. The idea here is to build only the
rooms you actually use, and then make each of them the size they need to be.
There is no perfect size house for everyone, and different lifestyles need
different amounts and kinds of spaces, although there are clearly common themes
that work for most people. The "three bedroom, two and a half bathroom" one size
fits all model no longer matches what a family looks like. In this
respect, you can’t know what the right size is unless you know yourself.
An exercise to do this is in the needs section.
Once the number of rooms is known, and the size of them is known they can be put together into one building. Doing so will almost always make the building bigger than the sum of the minimum sizes for each room. When trying to design small, a common occurrence is that a specific area of furniture, cabinets, or other interior uses forces at least one dimension of the room: for example a queen bed is 5' wide, and so to afford space to walk on either side, the minimum bedroom width is 9'. See building shape for more on putting the rooms into one package.
There is a temptation to believe that smaller (as measured in square feet of floor space) is better in terms of reducing environmental impact, and although its true, a difference of a few hundred square feet is often insignificant. The reason is that material use is heavily affected by the shape and complexity of the building as well as the surface area of the exterior. Heat loss is also a factor of the buildings surface area, but in practice in a superinsulated building is often dominated by window and ventilation losses. SO while 1000SF is certainly lower impact than 2000SF, it might not be that different from 1300SF. Given the same general shape, a smaller house is almost always has a lower environmental impact.
The size a house feels is depends on its layout almost as much as its actual size. A house whose rooms are just the right size avoids both wasting space and feeling cramped. By opening up a big area of public space so that there is a continuous line of sight, for example from the kitchen to the living room will make a small house feel bigger, as well as allowing for diagonal views from one space into another.
7) Building Shape
In deciding on the building shape you are making a tradeoff between two factors:
a square is the most efficient way to contain a given amount of space, both in
terms of the materials to build it, and to a lesser degree, the heat loss or
gain into it. But such a building is less than optimal in most climates
for solar gain (and preventing it), and can be difficult to get good daylight
into, because light only penetrates 12-15' into a room, and a room needs to have
light coming in from two directions, because light from a single direction
creates harsh shadows.
Size and shape are related because a house isn’t an amorphous collection of spaces, but is highly constrained to fit within a set of exterior walls. The final size can’t be determined until the spaces are organized into whole and tradeoffs of room size, floor plan layout and complexity of construction are also considered. Practical aspects like placement of heating systems and other utilities must also be considered. With all of this in mind, the desired look of the house must also be considered, and no matter what style the house is to be, a certain balance and rhythm of the components of the house must be achieved in order to get an attractive home.
A good method is to start with a box, then stretch it along the east/west axis until all the common areas can be accommodated. The rest of the rooms are then added along the north, facing east or west or on a wing from the common areas, typically in the shape of a "T" or "L". Bump rooms out or otherwise crinkle the edges so that every room can have good light.
In the process of making all the required spaces fit into a reasonable building shell, it is typical for the building to grow significantly beyond what size the space use exercise would indicate. When a plan has too much space that isn't working right, its time to rethink the whole layout from scratch in order to avoid too much of this inevitable space growth. In this process, think in terms of rooms having multiple uses, and of converting hallways into a useful space like a sitting area.
For daylight and solar gain purposes, usually a rectangle oriented so that the long axis is in the east west direction is best. For daylight purposes no room should be more than 15' deep. Other options for daylighting are to "crinkle" the edges, which especially helps allow light to penetrate from more than one direction (but beware unwanted solar gain). Larger buildings can be built with wings, and each wing should be no more than 25, or at more 30 feet wide. When this is not a good choice, two good alternatives are to use skylights, sun-tubes, and clerestory windows. The assumption is that the building can be oriented with 15° of south. If this is not possible, dealing with solar gain and daylighting will be trickier.
As the building shape emerges, keep in mind the connection to the street, maintaining the intimacy gradient, and how the landscape spaces will integrate with the indoor spaces near them.
8)
Adaptive Reuse2
No matter how generic you design a building, it will almost certainly
get remodeled at some point during its lifetime, and in many cases it will be
remodeled more than once (beyond just the painting and wallpaper type things).
Partly this is due to the fact that the average person only lives in a house for
seven years, and partly because both technology and a persons life situation
changes, each providing different motivation to remodel. Adaptive reuse is
about making a building that accommodates the kind of changes people are
likely to make over the lifetime of the building.
As a culture, we're not much for planning for the future, and with buildings whose lifetime is (hopefully) at least fifty years, the problem is all the more difficult, because it is difficult to know what future needs will be. Based on experience remodeling existing building, there are a few conclusions that can be drawn.
A quality house will always be more desirable than one build shoddily, even if the construction doesn't meet today's standards. When it comes to using structural materials, it doesn't pay to skimp, as over time houses have a tendency to sag. It does not seem likely that energy will ever be so abundant and cheap that being as energy efficient as possibly won't always make sense. Features of houses that are the "latest rage" tend to get eliminated in some way in the future. Houses that "feel" good to one generation are likely to be equally well received by successive ones, but the specific uses of the rooms is likely to change. Of all the aspects of a house, utilities are the ones that change the most, especially electric & electronics.
There are a number of levels of reuse, each using successively more of the existing building.
At the lowest level, the existing foundation and main floor platform can be reused, but nothing else is worth saving. Sometimes even this level can be due not cost effective, since it is generally cheaper and easier to build new than mess with an existing building.
The next level is to reuse the shell of an existing building, redoing the interior partitions and utilities. Since the shell is typically only about 25% of the total cost, there must be significant motivation to reuse it: either it has to be of significant architectural interest to make someone want to save it, or be close enough to the current construction quality that it can be used as is. Unless most of the window & door opening are in the right spot, a lot of rebuilding will need to be done.
The next level is to reuse the rooms more or less as they are, and make mostly cosmetic changes, as well as updating utilities, with electrical upgrades being the most common. Bedroom may become offices, kitchens and bathrooms often get updated, but most of the house is left intact. When a house has a good layout, people find clever ways of adapting room to the current needs. When a house can easily be expanded by adding a second floor or a wing, it is easier to reuse. Likewise, if an existing second floor or basement can become a separate residence, the house can be adapted in that way also.
Reuse at is best involves little changes other than decoration, although utilities are a constant problem. The most volatile aspect of this is the electric wiring for electronic devices: telephones, cable TV, alarm systems and computer networking. Although often have too few circuits, not enough telephone jacks and no internet or cable TV jacks, most people find ways around all these things, especially since upgrading them usually requires breaking open walls, fishing wires thru them, and patching them back up. A better choice would be to install an adaptable wiring system, but other than wire-mold which is often used in commercial buildings, or exposed conduit (often used in older masonry structures in Europe) there are not many options. Individuals have created systems of chases that are hidden behind baseboards, door casings or other decorative features that can be attached via screws so that access to the wiring is easy.
The ideal building system from the reuse point of view would be one of standardized components that simply bolts together, but since there are no such systems available, the next best thing is to make the building be a reasonably high quality. In the case of interior partitions, office building already are made of modular or easily modified components, but there is little motivation to do so in residential construction. Simple layouts that take into account many of the design patterns are more likely to get reused. The less complex the structure is (and hence the smaller number of load bearing walls), the easier it is to move interior walls around. Utility upgrades can best be accommodated if they are not a integral part of the building and can easily be accessed to change them. Open web floor trusses can make laying wiring, plumbing and ductwork easier, and creating access doors makes it even easier yet. Creating utility chases is another way to give easy access.
Experience indicates that the buildings most likely to be reused are those at the far ends of the spectrum: very cheap ones, because they're easy to remodel, and one with a high level of craftsmanship and a good design, because people value quality.
9) Hierarchy of spaces
In an ideal world, a house is a sequence of nested spaces, the outer
layer for strangers, then one for friends, then one for family and the innermost
one for yourself and your partner. This is referred to as an "intimacy gradient",
which is anchored at the front door. Spaces closest to the door are, by nature
the most public, and spaces furthest away are the most private. Although
many houses do a good job of separation of the public and private spaces, one or
two of the layers if often omitted.
Porches are the ideal place to meet strangers or people of only casual acquaintance, by functioning as outdoor rooms. Beyond the front door, a living room or family room is the gathering place of friends. Attached to this space is usually the kitchen, and depending on one’s preference, it can either be well connected to the guests, or separate, although it is rare to be at any gathering of people, and not find guests, often all of them, in the kitchen. Beyond this is the space reserved only for family and close friends.
It is often useful to think in terms of gathering spaces and quiet spaces in addition to whatever function the rooms might also have. Kitchens and great rooms are often gathering spaces, but not everyone wants them to work the same way. Common areas often lack a quiet area, but could really use one: for example, an alcove off the main area, possibly with doors that close. In general, people will gather where its convenient, when the room is big enough, where the sun is and when places are created that allow them to feel protected but still connected.
The "bubble map" of spaces is a good way to show the hierarchy of spaces and integrate that need with the needs of room connectivity, access to light and connection to outdoors. Outdoors should be included on the map. In this way, private indoor spaces connect to private outdoor spaces and public to public, so that public spaces generally face the street, while private face away. When this isn't possible, it shows areas where workarounds are needed.
Each of the layers of space should be separated in such a way as to present an emotional barrier that clearly delineates the transition between spaces. When two adjacent spaces are for activities that have different requirements for quiet, the boundary between them should also be a sound barrier.
10) Main entrance - doors
The location of the main entrance is one of the most significant
decisions you make because it defines the entry into the "intimacy gradient".
Almost everyone has gone to visit somewhere and had a little difficulty in
finding where the front door is, and felt at least a little uneasy in the
experience, so is important that the door is obvious so people can find it
easily. This is accomplished simply in many ways, like surrounding it by a
porch, having a prominent walk lead to it, or even making it large and bold.
If an auxiliary door is more obvious or more convenient, then it effectively becomes the front door. This happens often when a driveway or garage is located closer to another door. This isn't necessarily a problem as long as you've accounted for the traffic flow, and accounted for the its potential impact on the intimacy gradient. Some people prefer to have a separate informal entry, and while there is nothing inherently wrong with this, the alternative view is that if the "front" door has the right transitional spaces, the dirt problem is solved.3
A transition area between the street and the door allows for a transition between outdoors and indoors. Porches help, and also provide protection while unlocking the door, a place for wet boots, or to shake our your umbrella, and for guests while waiting for you to answer. The purpose of a foyer is as a further transition; a place to greet, put on and remove coats etc. It need not be large--even a tiny area with a more weatherproof floor is better than nothing at all.
While mud rooms are a good place to contain wet dirty clothes, they aren't aesthetically pleasing, so its best to make them an alcove off the entry, rather than forcing someone to walk thru them.
In urban areas, you will rarely have much choice about which way the entrance to your front door comes, although you can rotate it 90 degrees by building a corner porch. It is best if the door doesn't face into the prevailing weather.
11) Central Common Area
The entire house design revolves around the common areas, since they are
the center of most activity. In designing the common areas, it is
important that traffic flow between them be confined in some way, so there can
be various nooks on the edge where people can gather and not be interfered with. Most people will want the common areas to face south, because that is where the
sun is. A kitchen that faces east catches the morning light and avoid the
afternoon heat.
For most families, a formal living and dining room no longer make sense because we have a more informal lifestyle. Whenever there are guests, whether is be a small gathering or a large party, most of the people inevitably end up in the kitchen, both because the food is there and so is the host. A counter separating the kitchen and eating space can act as a divider so that food can still be being prepared while the guests can engage in conversation with getting in the way.
People have places in a home they tend to gravitate toward, and certain spots tend to support different activities. Larger open spaces are inculsionary and tend to be gathering places for conversation, listening to music or watching TV. Smaller spaces are more inviting to quiet activities like reading or one on one conversation, and unfortunately many homes neglect creating these spaces. In some cases, small spaces can be carved out of the larger space simply by clever placement of furniture. In any family where noise tends to dominate the living area, a separate :"away" room for quieter activities solves the problem nicely. Obviously, it is important that the away room feel like part of the public space, but still be somewhat isolated from its noise.
12) Roof
A pitched roof makes the most sense for any climate except very arid,
because gravity removes water from it fairly rapidly and so relying less on the
roofing material to keep the house dry. If the roof is oriented so that
the board sides face north & south, then the south side also provides a place to
mount solar PV panels and solar hot water collectors.
Truss roofs are a very material efficient way to build a roof, but also renders the attic space practically unusable, unless you use attic trusses, which are a nice compromise. This is especially relevant because most houses have less storage than the occupants would desire.4 The issue is that you're building this space anyhow, why not make some of it useful?
An attic room, directly under the roof are some of the most beloved rooms in the house since you can often listen to the rain falling on the roof. There is something about the odd angles and areas of low ceiling that accompany attic space that seems to give people a feeling of being in a hideaway or a nest. For this reason building some space in the attic is a good idea.
13) Private Spaces
In the exercise in "just the right size", you find how you use your
existing house, and while there may be much space unused, others may be
overused. Here are a few ideas on the kinds of space people typically need.
Everyone needs they're own space where they can escape the rest of the family to read, do projects, or just enjoy quiet, even if the space is just an alcove somewhere. Beware of using an alcove off the bedroom unless they can be well isolated, otherwise someone is bound to be reading or typing while the other is trying to sleep.
Children especially need a space where they can play and not be in the way, but also not isolated, because they don't like being isolated. Located play areas off the common space, but as far as possible from spaces where you want quiet.
A couple needs space also, and so it is good for them to be able to isolate themselves from children so they can have private time.
14) Number of Bathrooms
Some houses certainly seem to have too many bathroom, while others
clearly have too few, as anyone who has spend any amount of time sharing a
bathroom knows.
Visitors will always need access to a bathroom, and to make them most comfortable, the bathroom should be accessible without having the feeling of entering your private space, but not so public that it can't be used indiscreetly, in particular so that the act of entering and exiting the bathroom isn't clearly visible by all. While other cultures may be less shy about using the bathroom, Americans are terribly so, and many people find it embarrassing if anyone else even hears the toilet flush. If there is a guest bedroom located on the main floor, one bathroom can serve for both overnight guests and visitor. When this isn't the case, a simple powder room will serve the main floor well, and can fit comfortably in about 15sf. If the house is multiple stories, most people will want a main floor bathroom anyhow, to avoid having to walk upstairs all the time.
Most couples want their own bathroom, and often preferably isolated from the rest of the house as a "master suite". Ideally the bathroom is located adjacent to a walk in closet/dressing room.
If all there are bedrooms on the second floor beside the master bedroom, they will need an additional bathroom. Some people may want to have a separate bathroom for children only, but many will also find that to be unnecessary.
15) Flow/Halls
Hallways are often wasted space and so they should be avoided, but they also
make great transitional spaces. Rather than allowing this to be waste
space, thicken the hall a little, turning them into rooms in their own right. For
example, you could line a wall with bookcases, add a window seat, a small
desk or a mail sorting area. It can be a great way to make small
quiet, private spaces and use very few extra square feet.
Some rooms will have to allow for flow thru them, and so need to be sized to accommodate that. Knowing the people will want to take the shortest route (and so you can only get away with forcing a somewhat longer route without creating frustration), figure out what the flow pattern might be and make sure it doesn't interfere with the activity in the room.
16) Storage
Storage is usually an afterthought, often occupying leftover spaces, and
as a result there is often too little of it. Take an inventory of all the
things you access regularly and make sure there are place for them. Some
common items are: kitchen garbage, recycle and compost, canvas bags, plastic
bags and food; the vacuum, brooms and other cleaning supplies; shoes, coats,
umbrellas; office supplies, bills to be paid, checkbooks. When designing
kitchen cabinets, make space for a reasonable amount of dishes, pots and pans,
but no more. Finally leave your self a lot of extra storage, both easily
accessible from indoors (for things like holiday supplies and other rarely
accessed things) and from outdoors for garden tools etc. The attic and basement
are often ideal places to store things.
One particular area that is usually ignored is a place to store all the inevitable piles of paper that accumulate: magazines, newspaper, bills, requests from charities, invitations, coupons to local merchants, bank statements, tickets, community notices, outgoing mail, and even an occasional letter or card. Build a place for all of this, and you can keep it organized and it won't clutter you dining table and kitchen counter nearly as much.
While is has been argued that basement are no longer needed (they were originally used as root cellars), in an urban setting where land is expensive, a basement is a way to build space and keep the building footprint small.
17) Utilities
Utilities usually end up in the basement or garage, because there is no other
place for them. This is not a good idea because these spaces are usually unheated5,
so there is an energy penalty for doing so (although you can build an insulated
closet for the utilities, having it be a well insulated closet is non-trivial).
Its is best to centrally located utilities, somewhere in the heated space in heating dominated climates, and in the unheated space in cooling dominated climates. This allows you to capture the waste heat from the HVAC equipment (or avoid capturing it). If the hot water is centrally located, there will be a minimum amount of wasted water going to each fixture, and the hot water will get there faster.
Utilities should always be designed to keep pipes out of exterior walls, both to avoid heat loss in cold pipes and prevent pipe freeze in cold climates. If they do have to be in an exterior wall, they need to be very near the inside.
18) Home workshop
If you don't incorporate a place to repair or build things, then you
won't be able to. In cooperative housing there is usually a shared
workshop, although anyone who uses tools regularly is pretty picky about who
they get lent to.
19) Dressing room
Its make no sense to store your clothes one place and have to drag them
elsewhere to get dressed. Most men probably don't really care, but many
women enjoy having that space where they can contemplate their outfit without
feeling exposed. Walk in closets can function well as dressing rooms, and
are best when located adjacent to the bathroom.
As an environmentally minded person, walk-in closets seem like a waste of space, but in fact it is easy to compensate by making the bedroom smaller.
20) Staircase
Like storage and utilities, people often don't leave enough room for
staircases. You need not only enough room to get up and down, but a
suitable landing pad on both floors. You need to remember that a staircase
exists on both floors, and as a result the best way to locate additional
staircases it to stack them on top of each other.
Staircases often act as the transition between levels of intimacy, for example acting as the bridge between the common areas and bedrooms. Enclosing them completely tends to make them dark and a bit claustrophobic. Its best if they have some daylight into them, which can be achieved with a stairway window or just by opening up the walls on the top and bottom, which also has the effect of opening them up more like a funnel. Keep in mind that the more open they are, the more noise will carry between the floors, but also the easier warm air will flow out for stack effect cooling, so there is a tradeoff there.
Stairs can be a space on their own, functioning as a place to sit, if the bottom is wide enough, but you can get carried away with this. Those grand staircases may look impressive, but they're all space that mostly won't be used.
Most building codes won't let you build stairs that are either too steep or too shallow. The average stair is somewhere around 7-1/2" high and 11" wide (usually called rise and run). Steps less than 7-1/4" feel a bit shallow, over 7-3/4" feel a bit steep. Most building codes6 won't let you go over 8". Likewise, a width less than 10-1/2" might seem a bit narrow, and more than 11-1/2 a bit wide. Codes generally won't allow anything less than 10" wide. Note that a 10" run will result in an 11" tread, since the tread sticks out 1". A common rule of thumb is that rise+run=17-18"; the idea being that shorter steps result in a longer leg swing than taller ones.
Some people prefer the shorter 7" steps, but the general problem is that such a stairway occupies a larger footprint, and hence a larger building. Its probably safe to say it is not likely there will ever be general agreement on the topic. The whole issue of limiting stair design so that it accommodates the least common denominator of level of fitness and agility is quite offensive to some, and it fact it is not hard to find an older house with a greater than 8" rise.
For an eight foot ceiling, you usually end up with 13-14 steps, and around 15-16 for a nine foot ceiling. It is often the case that not every step is exactly the same (ie the space doesn't divide evenly), and in that case, a couple of steps are usually 1/8" higher or lower than the rest. You generally have to provide at least 6'8" head clearance at every step.
A loft or other small limited spaces can have a much steeper steps too them: potentially as steep as a ladder, and in this case building code is apparently OK that only agile bodied people can use it.
21) Children's Place
Children are both noisy and energetic, so you need to provide a place where they
can do that without disturbing everyone else. Any place that children
frequent effectively becomes their space, because it is their nature to be that
way, and some families find this acceptable. Most parents make their
bedroom, and often any home office off limits to children for just this reason,
and if that is your desire the rooms themselves should be placed so as to make
this easy to enforce. One strategy is to locate children's play areas between
their bedrooms and the common areas. In fact their bedrooms can be reduced
to only an alcove for a bed and a closet; the space saved can then go into a
play room.
Resources
Adaptable Reuse, Environmental Building News, V12 #2 Feb 2003
http://www.bensonwood.com/innovation/openbuilt.cfm example of an adaptable timber frame system.
http://www.bensonwood.com/innovation/fhb-oct.pdf article from Fine Homebuilding Oct 2006 on adaptable building
Notes
1: the majority of the info here is adapted from "A Pattern Language", Alexander, et al, where it appears in much more detail. The summary here is for those who don't want to read a few hundred pages, and won't spent the $50+ on the book in hopes of helping people build nicer buildings (where nicer means that the next owner is more likely to leave it as is).
2: the background for this is from "How Buildings Learn", Steward Brand.
3: front doors leading directly into the living room with no transition are common, and as a result many people in that situation don't use their front door. The problem can be mostly solved by building an enclosed entry porch.
4: it could be argued that most Americans have too much junk, but even with this alleviated, many houses would still have too little storage.
5:in hot climates, the basement or garage is actually the best place since then the waste heat goes outside, saving the air conditioner from having to move it outside.
6: there is considerable disagreement in building codes at the moment. Commercial buildings are limited to 7" rise, while residential rise is limited to either 8", 7-3/4" or 7" depending on what base code is referred to. Apparently a lot of bad accidents happen on stairs, but its not clear that the various changes in stair/railing code will actually make it any better, especially since some people just can not easily negotiate stair.