Floor Support Joists

Once we go beyond the allowable spans for floor joists as shown in the floor joist span tables we will need some kind of support under these floor joists.

Floor support joists.

This article provides step by step instructions and pictures on how to make structural repairs by sistering floor joists alongside weak joists. If you have sagging cracked or twisted joists which can happen in older houses this project will provide the extra support the floor needs. This support could take the form of a structural wall. In some cases additional joist supports will have to be installed before there can be extra heavy objects on the floor.

Span tables use these tables to determine rafter span ceiling joist span and floor joist span. The wall could be either a properly sized structural concrete or concrete block wall or a wood framed wall. Here we ll examine the rules. Plenty of trial and error plus a healthy dose of engineering and testing have gone into the official rules in the building code.

Still when framing a raised floor it s easier to think of floor joist spacing in terms of 12 16 or 24 inches on center because each joist is positioned along the header according to its center point. The joist support helps reinforce the floor so it can handle the weight load it needs to. Span tables and tables that show design limits for particular lumber types allow you to determine whether a given floor design will meet code and design requirements. This sample table gives minimum floor joist sizes for joists spaced at 16 inches and 24 inches on center o c for 2 grade lumber with 10 pounds per square foot of dead load and 40 pounds of live load which is typical of normal residential construction.

According to section r502 4 of the 2009 edition of the international residential code joists under parallel load bearing walls must be big enough to support the weight of the load they bear.