Loft Floor Joist Thickness

Loft floors loft floor construction.

Loft floor joist thickness. Existing loft joists are designed only to support ceiling boards so a structurally sound floor is needed. The width of a board is an important factor in determining the distance a floor joist can span playing a much larger role than the thickness. Though joists may be any size that you desire using typical floor joist and beam specifications ensures that you can find hardware to fit the joists and that the floor provides adequate support for furniture and other items in a room. Sistering is the process of adding a new joist next to each existing joist.

Joists insulation and boarding. Ceiling joists consist of two narrow low grade timbers often bolted together sistered above a supporting wall. Floor joists or beams provide the below surface support for the wood subfloor of a room. 7 16 15 32 and 1 2 inch thick panels require joists spaced 16 inches on center.

True floor joist span calculations can only be made by a structural engineer or contractor. For example if you double the thickness or number of joists in a floor the distance the boards can span will increase by approximately 25. In the case of 2x6 joists you can pair them up with additional 2x6 joists by nailing them together side by side. The thicknesses are as follows.

No matter what the spacing is on your ceiling joists 3 4 inch plywood should be used if you plan on walking on it. If you plan on placing the plywood around the perimeter of the opening or door and using it only to store light boxes or materials 1 2 inch thick plywood should suffice. If the attic joists are not adequate one way to strengthen the floor for live loads is to sister the old joists.