Attic Flooring 101: All You Need to Know – Bob Vila

With the high cost of new construction preventing homeowners from adding square footage to their homes, many are understandably looking to make existing space work harder for themincluding any unfinished space. Attics are a top pick when homeowners decide to gain some extra storage or add a guest room, but not all attic flooring structures are up to the task of supporting the weight of a new living space. If youve ever wondered whether or not your attic would support decking for storage or, even better, a loft conversion, keep reading. Well explain the most important factors and how to find out what you can safely do with your attic space.

A common misconception is thatit takes little more than the installation ofsome decking over the attic joists to ready an attic for move-in. In some houses, this may be the case; in many others, however, the original joist structure that supports the ceiling of the room beneath was never designed to hold anything more than the ceiling drywall. In part, it boils down to joists:

Beyond the size of joists, the spacing betweenthem shouldalsobe taken into consideration. Standard joist spacing for the installation of attic flooring materials is 16inches on center (OC), meaning the distance from the center of one joist to the center of the next joist is 16 inches. Joists in attics that were never intended for the installation of flooring or conversion to a living space are often 16 inches OC or 24inches OC.

If your existing attic flooring isnt adequate for conversion to a living space, all is not lost. Virtually any attic floor can be brought up to codeits just a matter of how much additional structural support it will require.

Modifying an attic floors joist system is a job for the pros. But before even they can start on a job that involvesaltering your homes structure, theyll almost certainly have to pull a permit. This involves submitting a plan of the intended modifications to the local building authority, who will analyze the plans and issue a remodeling permit if the plans meet building codes. Only then can they get to work.

The type of modifications selected for reinforcing the joists will depend on the recommendations of the engineer, but the following methods are commonly used to beef-up undersized attic joists:

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When houses are constructed, specific walls are selected to be load-bearing walls and designed to support the weight of the structure above them. Houses thathave been constructed with the idea of finishing out a future living space in the attic will not require joist reinforcement nor additional vertical reinforcement.

If your home wasnt designed to support a futureattic conversion, not only will the joist system require modification, an engineer may require additional vertical reinforcement installed in the floor(s) below the attic to support the new attic weight. This could involve installing structural posts in one or more areasof the home (which can often be hidden within an existing wall).

Other structural issues are also factors, including whether there is adequate space to install a stairway to the attic. Building code often requires stairway access to the attic if the space is to be used as a bedroom. If you intend to install only a sitting loft, you might get by with just a ladder.

The headroom in the attic will determine how much usable floor space you have. While local codes vary, many communities will not permit the ceiling in a finished living area (attics included) to be lower than 6 8 to 76 from the floor. That doesnt mean you cant use the attic areas where thesloped ceiling is lower;that space just wont count toward your homes official living space. For example, you could construct storage cabinets or cubbies in the low-sloped sides of the attic; when an appraiser measures the square footage of the finished attic, though, only the portion where the ceiling meets minimum height standards will be recorded as living space.

A limited amount of usable floor space can obviously impact how you intend to use the space. Small bedrooms are cozy set in an attic with slanted ceilings, butyou may want to reconsideryour plans if your usable floor space doesnt fitmuch more than a bed.

If your attic joists wont bear the weight necessary to finish out a living space but the engineer cleared them to support floor decking for light storage, you can install -inchplywood or oriented strand board (OSB) in 4-foot-by-8-foot panels over existing 16-inch OC joists.For joists spaced 24 inches OC, use thicker, -inch plywood to prevent sagging between them. If youre familiar with basic carpentry and framing techniques, installing decking for attic storage is a DIY-friendly project. Just remember:This type of attic flooring will providestorage spacefor overflow items and seasonal items, but it wont pass muster as a living space floor.

Attic flooring intended for a living space must be installed in compliance with building codes. Some communities will allow homeowners to do their own construction, but they are still subject to all inspections required by the building authority. Accepted floor decking for a living space is typically -inch tongue-and-groove subflooring, glued and screwed to the joists. The manufacturer of the subflooring may specify an attachment pattern, such as one screw every 6 inches along the edge of the panel and every 8 inches in the field (center of the panel).

Even if permitted by your community, converting an attic to a living space is a complex project that most homeowners are not prepared to tackle. It involves installing outlets, switches, and (potentially) water-supply lines and drainage pipes if a bathroom will be added. Attics are fresh-air ventilated so provisions must be made to reroute the attics ventilation through the rafter spaces and the rafters must then be insulated. An attic conversion is a great way to expand your homes living space, but best to leave the work to a licensed contractor.

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Attic Flooring 101: All You Need to Know - Bob Vila