Overlap rabbeting on exterior shutters is a groove along the vertical edge that allows one shutter to overlap the shutter next to it. An overlap rabbet is very much the same as what is termed as a shiplap joint or half lap joint.
Overlap rabbeting can be found on all functional exterior shutters and for a very good reason. With an overlap rabbet the shutters will close over one another eliminating any exposure in the center leaking rain, light or air . The overlap rabbet also creates a solidness to a closed pair of shutters locking them tighter together to eliminate any “shuddering” for better storm protection.
An overlap rabbet is just as important for interior shutters. With an overlap rabbet UV rays are blocked from damaging your room furnishings as well as providing a tighter seal over the window giving better energy efficiency. If you are using your interior shutters as blackout shutters for a bedroom or a media room overlap rabbeting is a must.
Overlap rabbeting is decorative, as well as functional, giving a neater and more finished appearance. If you look at the picture to the right you will see the half-round bead detail. This is shaped into the wood shutters to give a more uniform look to the face of the shutters. This type of rabbet is referred to as a beaded overlap rabbet.
A good rule of thumb, for both interior and exterior shutters, is to have an overlap rabbet if your shutters are meant to be functional or at least look functional. It is an option that adds very little to the cost but greatly increases their value.
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