What is a Flitch Beam?

Flitch beams are structural beams that are made up of a steel plate sandwiched between two wooden beams. Bolted together at regular intervals.

Garden Room flitch beam

The steel plate provides strength and rigidity, while the wooden beams help to distribute the load and reduce the overall weight of the beam. Flitch beams are commonly used in construction applications where high strength and stiffness are required, such as in floor joists, roof support structures, and heavy load-bearing applications.

Advantages of Flitch Beams

There are several advantages to using flitch beams, including:

  • Strength: Flitch beams are very strong and can support a lot of weight.
  • Stiffness: Flitch beams are also very stiff, which means they are less likely to warp or twist under load.
  • Weight: Flitch beams are lighter than solid steel beams, which can save on material costs and transportation costs.
  • Versatility: Flitch beams can be made to any custom size, which makes them well-suited for a variety of applications.

Disadvantages of Flitch Beams

There are also a few disadvantages to using flitch beams, including:

  • Cost: Flitch beams can be more expensive than other types of beams, such as glulam beams.
  • Labor: Flitch beams require more labor to install than other types of beams.
  • Durability: Flitch beams are not as durable as solid steel beams, and they can be damaged by moisture and rot.

Where are Flitch Beams Used?

Flitch beams are used in a variety of construction applications, including:

  • Floor joists: Flitch beams are often used as floor joists in commercial and residential buildings.
  • Roof support structures: Flitch beams are also used to support roofs in commercial and residential buildings.
  • Heavy load-bearing applications: Flitch beams are used in applications where high strength and stiffness are required, such as in bridges and retaining walls.

Flitch Beams in a Garden Room

Garden Room flitch beam

Flitch beams are a great way to overcome some of the issues when trying to build a garden room under the 2.5M height restrictions.

The 5×2″ timber used in the roof structure cannot be used for longer spans. larger timber is normally used, but this takes the height of the building over 2.5M.

A flitch beam can resolve this issue. By sandwiching a metal plate between the 5x2s, the beam is much stronger, without increasing the height of the beam.


Flitch beams are a versatile and strong type of structural beam that is well-suited for a variety of applications. However, they are more expensive and they require more labor to install.

More information is available here

If you would like to know more about the Garden Room height restrictions and permitted development, see our Garden room Planning permission guide below:

Frequently asked questions

How are Flitch beams made?

Flitch beams are made by first cutting the wooden beams to the desired length. The steel plate is then cut to the same length and sandwiched between the wooden beams. The beams are then bolted or welded together to form the flitch beam.

How are Flitch beams installed?

Flitch beams are installed in the same way as other types of beams. They are typically supported by columns or other structural members.

What is the lifespan of a Flitch beam?

The lifespan of a flitch beam depends on the materials used and the conditions in which it is exposed. In general, flitch beams can last for many years if they are properly maintained.

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