A cloister rebate — Dutch kloostersponning — is a rebate with a wide, usually U-shaped recess, for example in the underside of a floorboard or on the wall face of a window frame jamb. It is not a narrow rectangular rebate that something fits into, but a machined groove that removes part of the timber face.
The purpose is almost always the same: to avoid gaps. With less timber touching the substrate, small irregularities are bridged and the wood can move without cupping or binding.
Where it is used
- Floorboards — a wide groove in the underside lets the board bear only on its two edges, so it sits flat on the joists
- Sills and thresholds — the same principle: less contact area, fewer gaps
- Window and door frames — the wall face of the jamb gets a cloister rebate that is filled with mortar as the brickwork goes up, making the junction windtight
- Lightweight partitions — a wide U-groove in a stud that a wall panel slots into
Practical tips
- Leave enough timber — the two edges beside the groove carry the load; a groove that takes out most of the thickness invites splitting
- Fill the rebate in a frame completely — a partly filled rebate is a continuous draught path over the full height of the jamb
- Add an airtightness tape in new build — mortar alone does not stay airtight, because timber and masonry move differently
- Machine it in several passes — cutting a wide groove in one pass causes tear-out
Related terms
- Mortar rebate
- Glazing rebate
- Window frame
- Tongue and groove
- Airtight construction
- Threshold
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