The conversion of unfinished attics to year-round living space has been a constant in American homes for centuries. Fitting out an attic, however, comes with its own set of constraints and a checklist of dos and don’ts. The first constraint is that attic walls typically slant at sharp angles, cutting down the amount of usable space. You may find a lack of headroom, most notably in low-pitched or gable-ended attics. An attic remodel usually will require flooring, sheathing for walls and ceilings, stair access, and dormers or windows. Then come such big-ticket items as structural support, insulation and venting, plumbing for a bathroom, heating and air conditioning, and electrical service. In essence, you’ll be building a little house in the attic.
A complex job is defined by what’s missing: adequate headroom in most of the space, say, or lack of a staircase (or limited room to add one on the floor below). The older the house, the more likely that renovation will require increased structural support. You may even need to raise the roof.
The simplest conversions are those where the attic already has adequate headroom, a floor (or subfloor), adequate light and window space, and access by way of a fixed stair. Chances are the joists under the floor will need reinforcement, the stair may not meet modern building codes, and livability will demand more windows than the required minimum. If walls and ceilings are clad in beadboard—a common treatment in the attics of many early-20th-century houses—that will need to be removed so that insulation and wiring can go in.
Complex attic conversions are defined by what’s missing: adequate headroom in all or most of the space, or the lack of a staircase (or limited room to place one on the floor below). The older the house, the more likely the renovation will require increased structural support—both underneath the floor and between roof rafters. In some cases, adapting the attic for living space will mean raising the roof itself.
Other tough conversions include attics where trusses or the roof profile make it all but impossible to meet minimum head heights. Dormers and bump-outs can help, but they add substantially to the overall cost. From an architectural standpoint, they can also be tricky to design and place because they alter the roof profile.
“There are innumerable ways to do a dormer wrong and only a few ways to do a dormer right,” says architect Frank Shirley. A dormer should be large enough to bring in light, but not so tall or wide that it dominates the roofline. A shed dormer that runs the entire length of the roof reads as contemporary, as such dormers were rare before they appeared in 20th-century styles such as Dutch Colonials: “Historically, that’s not how dormers were done.”
A fixed staircase is an essential part of an attic that will be used every day. A back stair originally meant for servants is one option, but such stairs tend to be steep, narrow, and dark. If no stair exists, one solution is to stack the stair on the footprint of the one a level below. If that’s not possible, making room for the new stair may require moving a wall or giving up other space on the floor below. When the stair reaches the attic, it should arrive at a landing with railings.
Planning on including a bathroom? Placement is crucial here; ideally, for reasons of cost and disruption, the new fixtures should line up directly over a bathroom or plumbing lines below. Check with the local building department to make sure there’s enough headroom for a shower; if there isn’t, you may have to settle for a bathtub.
Finally comes the issue of how to clad all that slanting and sloping wall and ceiling space. While this is more of a design issue than a practical one, consider a historical cladding with relief and texture, like beadboard, tongue-and-groove planks, or even wallpaper. All have a long history in attic conversions.
A storey pole is a length of narrow board (usually cut to the height of one building storey) and marked with dimensions including windowsills and headers, joists, etc. It has been used traditionally as a layout tool for such repeated work in carpentry as stair-building, framing, siding, and bricklaying.
Up to Code
Any attic conversion is subject to building codes for safety reasons that may not at first be apparent, such as structural support and fire hazards. Other attic-specific requirements cover headroom, floor space, access and egress, windows and light, heating and cooling, and ventilation.
Headroom Attics in the oldest homes rarely meet modern codes for height, which require ceilings be at least 7 to 71/2‘. Yet some are barely 6′ tall. Other roofs are supported by trusses that cross the space at a midpoint between the floor and ridge pole, making minimum ceiling heights impossible. At least half of the usable space should have ceilings at least 7’ or higher. New flooring, insulation, and drywall or wood finishes may cut into the available room height.
Floor Space The minimum for a new attic room is 70 square feet. (The smallest dimension must at least 7′.) While that may seem tiny, consider that a significant amount of the footprint is usually tucked under eaves that are less than head height. As a good rule of thumb, make sure there is at least 70 square feet with an overhead height of at least 6′.
Support Attics in older homes were never intended to be load-bearing: that is, to hold the weight of people, furniture, and bathroom fixtures. Many were built with “dead load” weights of 10 pounds per square foot or less. Minimum live loads—the requirement for habitable space—are three or four times that. Meeting the standard will usually mean improving joist support under the floor and strengthening rafters overhead, and may even involve engineered improvements such as tie-rods. Complex projects will require a structural engineer.
Access and Egress How will you reach the attic? A fixed stair is usually a minimum requirement, along with a second point of access (usually a window). While it’s possible to buy a spiral-stair kit that meets code and fits in as little as 5 square feet, ask yourself whether you want to climb that stair every day, if the new space is intended as a main bedroom. What about getting furniture up to the space? Architect Frank Shirley says: “Spiral stairs are my last option to get from one floor to another.”
Windows & Light Codes require that at least one window be equal in dimension to 8 percent of the usable floor area. For 150 square feet of usable space, that equates to a small single window or skylight (3′ x 4′). In most cases, you’ll want multiple windows or skylights, one of which is large enough to permit escape in an emergency. In that instance, add a fire escape or escape ladder to the budget.
Heating & Cooling Any attic conversion must have a fixed source of heat (portable heaters usually don’t meet code) and be able to maintain a temperature of 68 degrees F. Since most attics tend to trap heat, it makes sense to add or extend whole-house HVAC to the attic, or to add a mini-split unit that serves the new space. For the same reason, it’s essential to insulate all walls and ceilings, either with spray-foam or batt insulation.
Ventilation Before spray foam or batt insulation goes in, create a 1″ air space from soffit to ridge by using rafter vents or insulation baffles. The vents create narrow gaps that allow fresh air from the soffit vents to flow up and out through the ridge vent, to avoid moisture problems.
Filling in Triangles
In an attic renovation, no space should go to waste. Turn the unused, triangle-shaped space close to the floor into runs for HVAC ductwork or electrical or plumbing lines, then conceal the works behind 3′ to 4′- high knee walls. Use taller and deeper knee walls for built-in storage such as drawers and cubbies. Finishing built-ins with period hardware and wood stains similar to those downstairs goes a long way toward making a frankly new space consistent with the rest of the house.
A Gambrel Attic
For a smallish, 200-year-old house overlooking the ocean north of Boston, the attic was the only place to expand. Even though the gable was so shallow that someone 6’ tall couldn’t stand upright at the ridge, zoning and conservation setbacks made any other type of addition to the two-storey, 1,600-square foot house impossible.
The solution was to literally raise the roof, giving it a gambrel profile. “We created a different roof that would have been appropriate for that time,” says architect Frank Shirley.
The new profile not only allowed the project to meet headroom requirements, but the shallow, slightly sloped sidewalls inside also are ideal for the placement of period-correct dormer windows that let in light.
Rebuilding the attic frame to support the new roof came with its own pitfalls. “The contractor actually had to work really fast, using trusses prebuilt on site so we could get the new roof on in just a couple of days.” Timing was essential to protect the finished rooms below.
Sometimes wood alone cannot support the weight of a reconfigured space. Here, “we introduced a structural bent, a steel beam that’s welded in the shape of a gambrel that occurs where those tie-rods are. That’s what’s keeping that gambrel roof upright,” the architect explains.
Tie-rods that run the full width of the house, and that work by tension, are a traditional means of ensuring structural integrity. “The turnbuckle in the middle allows a certain amount of tension in the tie-rod itself, but it shouldn’t be too tight.”
To the owners, the expansion was worth the trouble. Of the balcony, Shirley says: “That was 8 square feet of the best real estate ever built.”
Pro Tip: Dead loads are permanent loads that result from the weight of the structure itself or from other permanent attachments such as drywall, roof sheathing, and trusses. Live loads include people and furniture: anything that can move.
The Price of New Space
With residential remodeling costs leaping past $200 per square foot (up to $400 in some areas), it’s tempting to think expanding into the attic will save money over a conventional addition. That’s often not the case, especially if the existing space needs big-bucks remedies such as a new staircase or a roof dormer. Still, a walk-up attic that already has essentials including good headroom and stair access can be converted to modestly outfitted, usable space for about 75 percent of the cost of a new addition. Including a bathroom or high-end fittings such as custom-milled beadboard or top-grade flooring will add to the cost.
Lighting the Attic
An attic conversion is one place where recessed lighting makes sense, since the nearly flush fixtures save precious headroom. As long as there is enough clearance around the housing to meet fire codes, hockey puck-style lights can be nestled into the gaps between studs. Some recessed fixtures can be buried into insulation, but others cannot. Check the spec sheet before you buy.