Learn how to build girders in new house construction according to the 2012 International Building Codes. Find out how to position them exactly, straighten them to perfection, and fasten their plies permanently.
Flush Beam or Drop Girder?
Drop girders are positioned in such a fashion so that the floor joist sit directly on top of them. This is usually the same height as the pressure treated mud sill. Drop girders require a a slightly different set up in the foundation and the footing. The foundation will need notches sawed or formed into it for the girders ends. The piers will need to be built at a grade so the top of the pier will be a distance the same thickness as the girder below the bottom of the floor joists. Drop girders are also the only practical way to repair a week floor system.
Flush beams are built in such a fashion so that the the of the girder ends up the same level as the top of the joists. This type of girder requires the beam be notched where it rests on the foundation wall. It also requires either a ledger strip or joist hangers to assist in the permanent fastening of the joists. Be aware, while we prefer ledger strips (and they approved by the 2012 International Building Codes), they are prohibited in some locations. Joist hangers are also a must for all flush beams in all engineered silent floor systems.
How to Position a Girder
It is pretty simple to take a set of blue prints and compare the beam placements with the locations of the load bearing walls. They should match exactly. Note that even slight changes in the positioning of the walls have to be reflected in the placements of the girders. Even though codes will allow a little bit of off positioning between the beam and the wall, we do no recommend it at all.
As far as building girders and having them end up straight, use a string. It is that simple. Do not try it any other way unless you are completely sure of your method.
Fastening Together a Girder
There is a next generation of fasteners known as TimberLok screws. They are code compliant and are unequaled in their fastening strength. They are also easy to drive home with a quality cordless impact driver. If you are dead set on using nails only, then use plenty of them; at least a column of four for a 2 x 12 every sixteen inches apart on each ply. All LVL beams over two ply must be bolted.
