What Is a Flitch Plate?

In construction, a flitch plate is a steel plate that is sandwiched between wooden beams to increase the strength of the beam. A flitch plate is useful for reinforcing existing beams, as well as for adding substantial strength to new beams. However, with the advent of new composite lumbers that are equally as strong, the flitch plate system has largely become obsolete. Constructing these systems can prove to be labor-intensive, as they must be bolted together and cut to proper length beforehand or on the job site.

When a flitch plate is combined with two studs, it is called a flitch beam. It is then considered a composite construction material because it combines more than one material to form one unit. In order to make such a beam, the studs and the plate must both be cut to the proper length. This can add to the amount of labor involved in installing the beams, which adds cost to any project. The flitch plate can be pre-cut to length to be installed at a job site, but in some situations, it may need to be cut on the job site, which can be time-consuming and costly. Because of such restrictions, flitch beams have given way to composite studs that are made with wood fibers and glues that increase strength and decrease cost.

A flitch plate beam system has several advantages over a normal wooden beam, however. Because a flitch beam of the same length as a regular wooden beam is much stronger, a flitch beam does not have to be as deep as the regular beam. These beams make renovations much simpler, as they can be created out of existing beams rather than necessitating the old beam to be removed and completely replaced. They are lighter than full steel beams and more versatile in terms of installation--for example, because a flitch beam is still wood on the outside and steel only on the inside, the beam can be nailed or screwed to structures rather than welded.

In addition, a flitch beam's strength can be increased to the builder's needs by simply attaching more plates and more beams. This adds an element of versatility and customization useful in renovations and home additions. Flitch beams were commonly used as rafter beams in home roofs because they can carry a heavy load over long distances — commonly up to forty feet (12.2 meters). Using flitch rafters in roof support also offer the potential to eliminate ridge beam and post support altogether and offer a way to "open up" or vault a ceiling in place of conventional truss roof structures that typically result in flat ceilings.