what is a "check reveal"

[sm_jamieson]

Anyone know what a window "check reveal" is. I came across the term in relation to fitting windows in exposed positions. Cheers, Simon.

[Tony Bryer]

This is a guess, but I suspect it means that the outer skin of brickwork extends over the face of the window fame.

BBBBBBB WWWWWWWWWWWW BBBBBBBB

[Jim]

We have them on our house - it means that the window fits behind the outer skin of the cavity wall. If you'll excuse the ASCII art:

Normal: (out on top)

BBBBBWWWWWWWWWWWBBBBBBBB cavitWWWWWWWWWWWtycavity BBBBB BBBBBBBB

Check reveal:

BBBBBB BBBBBBBBB cavitWWWWWWWWWWWcavityca BBBBBWWWWWWWWWWWBBBBBBBB

The opening in the internal skin tends to be somewhat wider to accomodate the window frame. It works quite well with sliding sash since the sash box sits into the reveal.

You can see how the joint between window and brick is better protected from the weather. Although I suspect it's less of a relevant issue with modern technology.

The tricky bit is getting the details correct to minimise damp and cold bridging. The UPVC window installers that I've talked to are quite unfamiliar with the concept unfortunately. We ended up getting custom wooden windows made.

The sills can be tricky. You can get UPVC windows with sills which are long enough (they would need to have a projection of about 120mm to overlap the external brick) but they will probably need cutting to fit at the ends. We ended up using a cast concrete sub-sill to a custom design that I did.

Cavity closers (to stop cold bridging from the cavity through the window frame) to suit check reveal are difficult to get hold of.

It will look better if the window head has a concrete lintel rather than a steel one, because the steel lintel will be exposed.

[sm_jamieson]

Its interesting since building regs now want you to put the windows further back than before, projecting up to 30mm into the cavity area, so that the internal reveal is protected from cold bridging by more of the insulated cavity closer. This makes them harder to fix, and I'm making sure I get 70mm PVCu profiles so more of the frame is on the outer skin. The requirements leave more of the lintel visible as you described. It also means there is less amount of frame to prevent water tracking through. You can use the vertical DPC fixed to the insulated closers to create a "flap" alongside the window frame which would block any water tracking through. This vertical DPC would otherwise serve no purpose for PVCu windows, since unlike wood, they are waterproof. Simon.

[Jim]

You can get an combination cavity closer/DPC for sash windows:

've been unable to get samples or measurements though.