2x4 Attic Floor Joists

I can t imagine a garage layout that would have a span short enough to make with 2x4 s even sistered.

2x4 attic floor joists.

Often existing joist bays are filled with electrical and heating ducts that will need to be relocated. My calculations tell me assuming 2 southern yellow pine joists which are common in my area that 2x6s 16 inches on center will span 9 feet 9 inches with allowable deflection being the governing factor. The extra two inches of vertical distance when a floor is framed with 2 x 10 joists rather than 2 x 12s can be quite important for example. But you can still double the capacity of the existing 2x6s in the attic floor so first let s make sure that s enough for your situation.

Ceiling joists are typically 2 8 lumber floor joists are usually 2 10 or 2x 12 lumber. Positioning the new joist adjacent to the existing preserves precious ceiling but it does come with some potential complications. If your attic joists won t 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 inch plywood or. There are online span calculators available that tell you the maximum span for.

If you want to put down flooring in your attic and want more insulation underneath that floor then you need to increase your joist size. Is an attic with only 2x4 joists holding up the ceiling strong enough to use for storage. The studs in question span 16. Sistering 2x6 joists next to your current 2x4 joists will simply give you a new floor height of 5 1 2 inches as opposed to the current 3 1 2 inches.

That s a big size and strength difference between the two types of attic joists even if the joist spacing is the same. If the attic joists are not adequate one way to strengthen the floor for live loads is to sister the old joists. You d also have to have the attachments to the top plate of the walls adequate to support the weight of the floor. There is a wall under part of the attic which helps support the studs at approximately midspan.

The depth or height of your floor joists depends on how far they can span without sagging. If one end of the span is supported by a beam up the middle of the garage that probably wasn t sized to support a floor either. Sistering is the process of adding a new joist next to each existing joist. This is not a load bearing wall.

Common sense tells you that large floor joists can carry more load and spacing joists closer together also increases the load bearing capacity of a floor. Strengthening attic joists for live loads by sistering. Can it support an attic ladder and have some plywood put down and used as a storage area. But larger is not always better when builders are constructing a home or adding a room addition.