Stormproof windows are probably the most widely used of all modern windows.  Either in single or double glazed form Stormproof windows feature an outwards rebate of which the casement overlaps the front face of the window frame giving the window added water protection.

Storm Proof Windows are double glazed and fully draugh proofed and conform to Part L of the Building Regulations.

The cills extensions on the frames are best made of suitable hardwood such as Mahogany, Oak etc.  The drip under the front edge of the sub cill is an essential feature to prevent the tailing back of water under the cill.  There can also be a groove ploughed into the inside face of the cill for the cill to received the back edge of a window board.

Drip moulds are rebated into the dead of the window frame and are necessary to throw rainwater clear of the opening.