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Commercial Building-in Details

One of the great advantages of commercial framing is that it provides architects and designers with a tremendous range of design solutions and features a very flexible and simple fabrication assembly process. In particular most of Lidco’s framing systems are designed specifically to be square cut and require minimal end machining.

In general framing systems consist of continuous vertical elements (jambs and mullions) with the horizontal elements (heads, transoms, midrails and sills) fitting between the vertical elements. In cases where the horizontal sections are continuous and the verticals in between, it may be for design reasons or improved weathering. However, this alternative fabrication methodology results in limited expansion range and additional machining to the vertical sections. Also, the transportation of the frames to the building site is rendered more difficult.

Aluminium expands and contracts at the rate of approximately 1mm per metre of length and hence longs runs of commercial framing need to allow for this movement. In particular, where the distance between the mullions exceeds 900mm, expansion mullions are usually chosen and set with a nominal gap of 2mm.

In most cases the framing systems are supplied to site in unglazed modules and then clipped together side by side into their final location. Glazing usually is undertaken when all the framing has been assembled.


Sub-framing (subheads, sub-jambs and sub-sills) is used to simplify installation, improve weather performance and control air infiltration. In particular, subheads should be used where there is likely to be vertical movement due to slab deflection or settlement and, when used with sub-sills simplify installation.


Commercial framing is designed generally to direct water through and underneath the frame. It is not designed to be watertight and the use of slotted sub-sills is key to drainage control.

Sub-Sill End Caps

It is critical that the sub-sills be slotted and a stop end be used on sub-sills. Failure to do this will most likely resulting water over spilling the ends of the sub-sill and runs underneath the walls.

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