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Attic Conversions: Regulations and Requirements
Attic Conversion Requirements

Attic Ready for Conversion

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With the cost of fully-fledged home additions costing $75,000 rock-bottom minimum and usually far higher, many homeowners look for ways to increase their living space without depleting their bank account. There are two methods: expand the home's footprint or work within the footprint.

Expanding the footprint means putting on a traditional addition or a smaller bumpout--both costly because new foundations can be involved. Working within the existing footprint means a basement remodel or, looking upward, an attic conversion.

Like basement remodels, attic conversions have a few restrictions that make them not as attractive as they might first appear. But if you can clear these hurdles, attic conversions just might be a way to add space without spending a lot of money.

Attic Conversion Space Regulations

The first requirement--space--is often a deal-breaker for many homeowners.

To satisfy building code, you need to have enough space in your planned attic conversion to meet these following regulations:

  1. 70 square feet or more of floor space.
  2. At least 7 feet in any direction. This would translate to a bare minimum of 7' x 10'.
  3. At least half of the floor space should have a ceiling height of 7.5 ft. or more.
The purpose of these requirements is to avoid homeowners building strangely-configured and potentially dangerous spaces. As an example, a person might try to meet the 70 sq. ft. requirement by having a floor space that is 2' x 35' (Not allowed, per Requirement #2).

Require Roof Rafters, Not Trusses

Another factor that determines whether you can convert your attic is the presence of roof rafters vs. roof trusses.

Traditional rafters look like triangles; trusses look like triangles with smaller triangles inside of them (the boards forming these small triangles are called chords and webs).

Trusses are considered a superior method of framing a roof because of the additional support. Ironically, though, it's the rafters that provide a better environment for an attic conversion because of the clear space.

If you have trusses, it will be next-to-impossible to reconfigure them to allow for clear space. You'll be better off looking for other areas in your house to expand.

The photo above shows an attic with rafters.

Flooring Requirements

Your attic floor was probably built with dead loads in mind. Dead loads are things that do not move: boxes, trunks, suitcases, etc. Live loads are people and animals, and tangentially, the things used by people.

In rare cases, especially in new-construction homes, the attic may have been built unfinished, with the correct flooring in place, with the idea that the homeowner could later on finish the space.

In most cases, though, the joists cannot support live loads and may not even be covered with boards. You might open up your attic and find bare joists with fiberglass or cellulose insulation between the joists.

Fortunately, this is a fairly easy fix. You can sister the joists by cutting 2'x8' boards the same length as the joists, applying construction adhesive, and affixing each to a joist with nails. Then, after running any needed electrical wires or plumbing pipes, you will lay down 1/2" A/C-graded plywood subfloor.

Provide Suitable Access

Your attic may presently have a fixed ladder, a pull-down ladder, or no ladder at all. What your attic probably does not have is a set of code-compliant stairs.

To convert your attic to living space, you cannot provide access via a ladder. The staircase must:

  1. Provide a minimum of 6'8" of headroom the entire walking length of the stairs.
  2. Be at least 36" wide.
  3. Have treads of at least 10" deep.
  4. Have risers that are at least 7 1/4" high.

Have an Egress Point

Attics are the worst place to be in a fire, because heat and fire rise--rapidly. Since the staircase to the attic can act as a chimney for the fire to quickly spread, it's necessary to have a secondary point of egress, or exit.

In most codes, this means an opening (not fixed) window to the outside. If you plan to install a dormer in your attic conversion, this will automatically take care of the egress requirement, as most dormers include a window.

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