Flitch beam
The word 'flitch' refers to a plank of timber, cut lengthways from a tree trunk. It is related to the word 'flesh'.
A flitch beam is a compound beam commonly used in loft conversions and other timber-frame structures where longer spans are required than solid timber is able to provide.
Flitch beams consist of a steel plate sandwiched between two solid timber members and bolted together. Further alternating layers of timber and steel can be used as required to increase the strength of the beam.
The benefit of using flitch beams is that they are lighter and cheaper than using only steel, and allow fixing of the surrounding timber framework using nails or screws. As they are significantly stronger than timber beams they require less depth than a timber-only beam of the same strength.
In contemporary construction, the use of flitch beams has fallen into decline. This is largely due to the high cost of labour involved in their manufacture, and the introduction of high-strength engineered lumber and glulam beams. However, they can still be used to offer design versatility, and in renovation works where a structure needs to be altered or strengthened without increasing its depth or underlying construction.
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