A Decision Maker's Guide to Attic Remodeling

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Plumbing

If you'd like to put a bathroom in your remodeled attic, there are a number of restrictions you'll need to consider. First, are your water-supply and waste-disposal systems adequate? If you get your water by gravity, or even from a shallow well that is some distance below your house, you may find that the extra 8' or so of elevation will reduce water pressure to an annoying degree. (Every 2' of elevation is equal to 1 pound per square inch in pressure.) If you use a septic system for waste disposal, is it large enough to handle the extra water?

Plumbing layout can also present problems. Supply lines are small, so they can usually run laterally through holes or notches in floor joists, but this isn't possible for 1 1/2" to 4" drains. Code forbids any joist notching in the middle 1/3 of span and allows you to remove only 1/6 of their depth in the other 2/3. You may not drill a hole any larger than 2 1/2" in a joist or any closer than 2 1/2" from the top or bottom. Thus, unless your waste lines can run parallel to the joists, you'll have to raise the floor.

Then there's the matter of connecting to the house's main systems. You may be able to run supply and waste lines into plumbing on the floor below, but the new fixtures will have to be as near as possible to directly above the existing ones in order to use the existing plumbing vents. Plumbing code restrictions on the distance between fixtures and vents need careful study.

ATTICIf possible, lay out plumbing waste lines parallel to the joists.

Ceiling Insulation and Ventilation

Most houses with attics have their roof insulation laid between the ceiling joists because that's the easiest place to put it. When you finish the attic, though, the thermal barrier will have to go between (or on) the rafters.

Will there be enough depth between the rafters to get an adequate thickness of insulation? Most regional codes require at least R-19 in the roof—the equivalent of 6" fiberglass or high-grade 3" rigid foam. Find out what is required in your area, and use at least that much.

To ventilate properly, a 1 " space must be left between the top of the insulation and the underside of the roof sheathing. The air circulation thus created reduces condensation in the insulation during winter and heat buildup in the roofing materials during summer. In fact, your remodeling job must allow for a continuous circulation of air through all areas between the new living space and the roof. If you keep (or install) collar ties to form a flat ceiling, you can vent through gable ends using openings equal to 1/300 of the ceiling area. Air must be able to move from the area behind knee walls, over the top of the insulation, to the space over the collar ties, and out the gable end vents.

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