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What You Need to Know About Attic Flooring

Ever think about your attic as more than a place to store old items?

After all, attics can be great for anything from a guest bedroom to a kids’ playroom.

But before converting an attic, here are some considerations homeowners must make before laying out just any old flooring in the attic.

Attic Flooring Considerations

Unfinished spaces, such as attics, are prime spots for expanding living space. However, the high cost of new construction discourages many homeowners from adding square footage to their homes.

Additions are costly and there is no guarantee the homeowner will ever get his or her money out of the project. 

Many solve this conundrum by looking for ways to repurpose existing space to get more out of the current square footage. If you are wondering whether or not your attic would be a candidate for reprosing, such as adding decking for storage or a loft conversion, keep reading.

Below I explain the most important parts of an attic repurposing and how you can safely repurpose your attic space.

Can You Add Attic Flooring?

Many uninitiated homeowners think it takes just some insulation and some decking over the attic joists to get the attic ready as an office, bedroom, or study. In some houses, this may be the case.

However, in many others, the original joist structure that supports the ceiling of the room beneath is incapable of holding anything more than the ceiling drywall.

Can Your Attic Floor Support Enough Weight?

In part, it comes down to the joists:

  • If your joists are 2x6s or 2x8s, they are not adequate for supporting attic flooring in a new living area (and the furnishings and humans who will use them).
  • If the joists are larger, they might support attic flooring, but the only reliable way to know for sure is to have a structural engineer take a look at your attic support system. In some cases, even larger joists will not support a new living area, so it’s vital that an engineer take a look.

In addition to the size of joists, the spacing between them also needs to be considered. Average joist spacing for the installation of attic flooring materials is 16 inches on center (OC). This means the distance from the center of one joist to the center of the next joist equals 16 inches.

Joists in attics that were built without the intention of the installation of flooring or conversion to a living are usually 16 inches or 24 inches OC. When this is the case, additional work on the joist is necessary to prepare the attic flooring for repurposing.

If your existing attic flooring was not set up to accommodate living space, you can still complete the conversion safely, with a little extra work. Virtually any attic floor can be brought up to code. You just need to add the necessary structural support.

Bringing The Floor Up To Code

Unfortunately for DIYers who are not highly experienced, modifying an attic floor’s joist system requires a professional. Before an experienced DIYer or contractor can start on buffing up your floor joists, they need to pull a permit. This type of job involves altering your home’s structure, so most jurisdictions require a building permit.

To get the permit, the contractor must submit a plan of the intended modifications to the local building authority, another reason why most DIYers are not qualified for this type of job. The local building authority will analyze the plans and issue a remodeling permit, provided the plans meet building codes. Then the contractor can start work.

The modifications needed to reinforce the joists depends on the recommendations of the structural engineer, who will need to write a report before the contractor can create the plans needed to obtain the permit. The following methods are commonly employed to buff up undersized attic joists:

  • Bridging: If the existing joist system is close to being sufficient to support a new attic flooring, the addition of bridging between the joists may be all that’s needed.. Bridging involves cutting new wood members and installing them perpendicularly between existing joists. Bridging serves to stabilize the joists and reduces sagging. Bridging is usually installed in every joist space, and multiple bridge members may be required.
  • Sistered Joists: Depending on the existing attic structure, your contractor may be able to “sister” the current joists. This works by attaching new joists of the same dimension beside them. Sistered joists rest on the same load-bearing walls as the existing joists, but they also attach directly to the old joists. The two are bolted together to reduce the risk of sagging or breakage.
  • Addition of LVLs: Laminated veneer lumber (LVL) is manufactured through a heat and pressure process that yields wood beams that are much stronger for their size than regular wood. Depending on your attic structure, an engineer may recommend the installation of LVLs between the existing joists in order to bring the floor structure up to code.
  • Addition of Engineered I-Joists: I-joists, so named because they resemble the capital letter “I” from the end, are designed to support typical floor loads. An engineer may recommend installing I-joists above or alongside the existing joists to add structural support.

Other Structural Considerations

When builders construct homes, they select specific types of load bearing walls that are designed to support the weight of the structure above them. If a house was constructed with the idea of finishing the attic in the future, the selected walls will be adequate and you will not need joist reinforcement or additional vertical reinforcement.

If your home was designed for the attic to remain an unfinished space, the contractor will need to modify the floor joists and an engineer may be needed to plan additional vertical reinforcement installed in the floor(s) below the attic, which will support the additional weight added by the conversion. This work may involve installing structural posts in one or more areas of the home. If you are worried about unsightly posts, many times, these posts can be hidden inside an existing wall.

Other structural considerations include whether there is adequate space for the installation of an attic stairway. In many areas, building codes require stairway access if the space is to be used as a bedroom. This makes sense if you consider the possibility of a fire. If you intend to use the area for another purpose, such as a sitting loft, your area’s building codes may allow you to skip the staircase and just install a ladder.

Considering Usable Floor Space

Headroom determines how much usable floor space you have. While local codes vary, many areas require the ceiling of a finished living area (attics included) to be at least 6’ 8” to 7’6” from the floor. You can still use space where a sloped ceiling lessens the ceiling height below these levels, but those sections of the attic are not counted in your home’s official living space.

For example, you can add storage cabinets or cubbies in the low-sloped sides of the attic. When an appraiser measures the square footage of the finished attic, only the portion where the ceiling meets minimum height standards are marked as living space.

If you have limited attic floor space, you may not be able to make some types of conversions work. A cozy small bedroom can be a great attic conversion idea, but only if you have adequate floor space for more than a bed. 

Installing Attic Flooring For Light Storage Only

If your current attic joists are insufficient to bear the weight of living space but your engineer has cleared them to support floor decking for light storage, you can have your contractor install ½-inch plywood or oriented strand board (OSB) in 4-foot-by-8-foot panels over existing 16-inch OC joists, which are sufficient for light storage needs.

For joists spaced 24 inches OC, use the thicker, ¾-inch plywood to prevent sagging. For those familiar with basic carpentry and framing techniques, installing decking for attic storage is a DIY-friendly project. But remember: This type of attic flooring is sufficient for overflow items and seasonal storage, but it will never support a living space floor.

Attic conversions are a great way to increase living space without going to the expense of an addition. As such, you should always consider the options for your attic, especially if you live in an area where real estate values are high. But before embarking on an attic conversion project, consider the current flooring situation.

If your floor joist and wall supports are insufficient to support the load needed for a living space, you will need to shore them up first, which will require some engineering work and an experienced contractor.

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