Attic conversions and bonus rooms

The assessment records the attic as it stands: the framing, the joists, the headroom and the way up. The drawings that come out of design are yours to keep. Your private online workspace keeps each choice on record, along with why you made it.

Three kinds of attic room

How an attic becomes a room

Your choices up there

• What the room is for: a bedroom, an office or a playroom
• Where the stair lands on the floor below
• A vented roof or a sealed one
• Heating and cooling from the system you have, a new zone or a unit for the room, as the load calculation allows
• Closets, and storage behind the kneewalls
• Lights, outlets and where the switches go
• Whether to seal the room to an airtightness target

Under the roof you have

We finish space inside the roof your house already has. A new floor built up over a garage wing is a second-story addition. Add a kitchen and its own door, and your town's rules for a second home on the lot can come into play. In-law suites and garage apartments cover that path.

Hidden damage is an allowance.

Old roof leaks and damaged framing can hide under attic insulation and flooring. Damage that only shows once the work opens it up is carried as an allowance in the price.

Older attics get two checks.

A house built before 1978 falls under North Carolina's lead-safe renovation rules. Old loose-fill insulation in an attic can hold asbestos. On an older house, that insulation and other suspect materials are tested by an NC-accredited inspector before the work disturbs them.

Staying home during the work

Whether you stay home depends on the size of the job, and we settle it for each project. A large one may require moving out. A smaller one may be finished while you stay in the house. Living through it shows how work is planned around a household.

Code in force

The North Carolina Residential Code. New work meets the rules for new construction, and the existing house can stay as built if the work leaves it safe (Section R102.7.1)

Live load

Joists under an attic with no storage are designed for 10 pounds per square foot, or 20 with limited storage. A habitable attic or a bedroom gets 30 (Table R301.5)

Room size

At least 70 square feet, and 7 feet across in every direction. Under a sloped ceiling, at least half of that needs 7 feet of headroom (Sections R304, R305)

Building permit

Needed at any cost once the work strengthens the floor framing or adds wiring, heating or cooling (G.S. 160D-1110)

Design wind speed

Brunswick and New Hanover: 140 mph west of US 17 and 150 mph east of it. Pender: 130 mph, apart from Topsail Township at 140 west of the Intracoastal Waterway and 150 east (Table R301.2(4))

Your ceiling joists become a floor.

Many attic floors are ceiling joists. They were sized to hold up a ceiling, under an attic no one lives in. A floor that people sleep, work and play on is designed for a heavier load. So the joists often need strengthening to the plan, with added or deeper joists or a new beam. Where they would run past the span tables in the code, they are engineered.

Headroom is counted by the floor under it.

A room up there needs at least 70 square feet of floor. Under a sloped ceiling, at least half of that needs a 7-foot ceiling. Floor where the ceiling drops below 5 feet doesn't count toward the room's size. So a steep roof with a tall peak leaves more usable room than a low, shallow one.

Stand at the middle of your attic, under the peak. How much of the floor around you has room to stand up straight?

The roof's wind ties cross the room.

Where the code's coastal rule for roof ties applies, as in the 150 mph zone, the roof is braced from inside the attic. A board runs down from the middle of every third rafter, at most 4 feet apart, to the ceiling joists below. Near the peak, a collar or wind beam ties the rafters together. Those boards stand in the space your room will fill, so where they land shapes the layout. The code also accepts an equal or better way to tie the house together, designed for that house by an engineer or architect.

Plan on a permit.

State law exempts some jobs of $40,000 or less from the building permit, when the work meets code. An attic finish rarely fits that exemption. Strengthening floor joists is load-bearing work, and new wiring, heating or cooling falls outside it too. Your town's zoning or a historic district can have a say as well.

Your town may count the attic.

On the oceanfront

On an oceanfront lot, the state counts heated living space when it sets how far back from the ocean a house must sit. A finished, heated attic joins that count. On those lots, it's a question for a permit officer under the state's coastal law (CAMA) first.

In a flood zone

In a mapped flood zone, the framing, finishes and systems of an attic finish count toward your town's 50 percent rule. So does other work done in the town's counting window.

Stair

At least 36 inches wide, with risers no taller than 8 1/4 inches and treads at least 9 inches deep. Headroom of 6 feet 8 inches, and a floor or landing at the top and bottom (Section R311.7)

Escape window

At least 4 square feet of clear opening, 22 inches high and 20 inches wide. Upstairs, it also needs 5.7 square feet of glass, and its sill sits no more than 44 inches above the floor (Section R310.2)

Alarms

Permitted work brings every smoke alarm in the house up to new-house placement, with one on the attic level. Carbon monoxide alarms follow the same rule (Sections R314.2.2, R315.2.2)

Septic

Sized at 120 gallons a day per bedroom. A new bedroom on a septic lot goes to the county health department before the building permit (15A NCAC 18E)

The stair needs room on the floor below.

A stair to the attic needs a run of floor on the level below, headroom over every step and a landing at each end. In a house with 8-foot ceilings, even the steepest straight stair the code allows runs about 9 feet across the floor. That space comes out of a hall, a closet or part of a room. Where would yours land?

A spiral stair is allowed where the plan is tight. A ship's ladder can't serve as the room's way down.

Every attic room gets a window to climb out of.

The code asks for an escape opening in every bedroom and every habitable attic, its name for a finished attic room. Under a roof, the sill height is the hard part, since it can sit no more than 44 inches above the floor. A gable end wall is the usual place for a window that low. So where that window can go helps decide what the attic can become.

East of the Intracoastal Waterway, a new window also needs protection from wind-blown debris. Impact windows and doors covers the ratings.

If guests sleep there, it's a bedroom.

An office or a playroom up there already gets the escape window and a smoke alarm on the attic level. A room someone sleeps in also needs an alarm inside it, and on a septic lot, the health department has a say. If anyone will sleep up there, guests included, we build it to the bedroom rules from the start.

On septic, the health department comes first.

Septic rules count bedrooms, and each one adds 120 gallons a day to what the system must handle. So an attic bedroom on a septic lot needs the county health department to approve the system for it. That application comes before the building permit. Many lots around Rocky Point and Boiling Spring Lakes use septic. On sewer, as across Oak Island, the step drops away.

A room over the garage

The garage ceiling under the room becomes a fire separation. For a room over a garage, the code's table calls for 5/8-inch Type X drywall there. In a house built before 2012, existing drywall at least 1/2 inch thick is accepted there, with taped joints. No door may open from the garage straight into a bedroom. Ducts through that ceiling are sheet steel, with no openings into the garage. The stair comes up from inside the house, since the way out may not pass through the garage.

The insulation moves up to the roof.

Today your insulation likely lies on the attic floor, and the attic above it bakes. A room up there moves the insulated, sealed edge of the house to the roof slope, the kneewalls and the ceiling at the top. For a converted attic, the state's energy rules call for R-30 or more in the ceilings. The walls get the level set for outside walls (Section N1109.1.1).

A vented roof or a sealed one

A vented roof keeps an air channel between the insulation and the roof deck, so outside air can carry heat and damp away. A sealed roof puts the insulation right against the underside of the deck and brings the whole attic inside the house (Section R806.5). On a hot, humid coast, that choice shapes the rest of the insulation plan, and we make it with you.

Moisture management covers how a coastal house drains and dries. Our article on moisture planning before year eight follows damp through an older house.

Kneewalls are closed in on the attic side.

Behind a kneewall sits a strip of leftover attic, hot in summer. The wall's insulation gets a rigid sheet or an air barrier on that attic side (Section N1102.2.15). Storage doors through the kneewall are weatherstripped and insulated (Section N1102.2.4).

A tenth of the cost goes to the energy code.

Finishing an attic turns unheated space into part of the house. Once that job costs more than $10,000, a tenth of its cost is spent on meeting the energy code (Section N1109.2).

Heating and cooling sized for the room

Heating and cooling is a permitted trade in North Carolina, like wiring and plumbing. The HVAC trade sizes the system from a load calculation for the house with the new room in it. It installs the work under its own permit. That math picks between the system you have, a new zone or a unit for the room. The code also bars added rooms from overloading the old system.

If the air handler lives in the attic now, the room keeps a clear path to it and space to work on it. Right-sized systems explains how sizing keeps the air dry.