What is a petje?
A petje is a Dutch building term for a framed-out panel built in the inner leaf above a window frame, running up to the underside of the floor above. At that point no lintel is fitted: the frame simply closes the strip between the window head and the soffit.
The word means “little cap” — the panel sits above the window frame like a cap.
Why a frame instead of a lintel
Above a window frame the masonry or internal wall has to be supported. Normally a lintel does that. But if the distance between the head of the frame and the underside of the floor is small, there is barely any wall left to carry. A structural lintel is then unnecessary, and the strip can simply be closed off with a light frame and board.
A practical rule of thumb from site: around a metre of height above the frame is the tipping point. Below that, a framed panel is usually cheaper and faster; above it, a lintel with masonry becomes the logical answer.
Construction
- Frame. Timber battens or metal sections, fixed to the window frame, the reveals and the soffit.
- Board. Plasterboard or equivalent, finished on the face side.
- Junctions. The joint between panel and frame, and between panel and soffit, is the critical detail: movement and settlement cause cracking here. Either detail it as a crack-free junction or set a deliberate shadow gap.
- Airtightness. A petje is neither load-bearing nor airtight. In the external envelope the airtight layer has to be assured separately; carry the membrane or sealant line through behind the panel.
- Fire and sound. In a separating wall the panel must not break the fire resistance or the sound insulation of that wall. Fill the void behind it in line with the wall manufacturer’s system detail.
Related terms
- Lintel
- Window frame
- Inner leaf
- Cavity wall
- Reveal
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