Lantern trimmers


Lantern trimmers


Lantern trimmers

Roof lanterns in flat roofs have become very popular.  They can allow a lot of light into what may otherwise be a dark room.  However, the lantern does need to be properly supported.  This is done by designing trimmers to frame the opening.  The lantern trimmers may be either timber joists or steel beams.  It all depends on the size of the lantern and the span of the trimmers.

Structural calculations for lantern trimmers are normally required by Building Control. For small lanterns it may be enough to simply double up the joists framing the lantern.  However, for larger lanterns this is often not enough. In either case the trimmers need to be properly designed like any other part of the structure.

As well as the trimmers, we can also design the roof joists if required.  This makes it possible for us to make sure the depth of the trimmers will fit in the roof void.

Information required to design lantern trimmers

architectural layouts showing the supporting walls

the size and position of the roof lantern

manufacturers specification for the lantern (if available)

Design information