A pierced parapet and what hides behind it
St Peter's tower shows how often a roof most at risk is the one nobody can see.
The Church of St Peter has a three-stage tower of the East Mendip type, with pinnacles and a pierced, embattled parapet. A pierced parapet is cut through with openings, usually in a pattern, and embattled means it is shaped like a castle wall. It is a decorative edge on top of a roof, and behind it lies a plain engineering problem, which is where the rain goes.
On a building with a parapet, the roof slopes towards the wall, and the water collects in a channel behind it. That channel is called a parapet gutter, and it is usually lined with sheet lead. At each end or at intervals, an outlet takes the water through the wall and into a downpipe. If the lead splits, the water goes into the masonry. If the outlet clogs, the gutter fills and overflows into the building. Both failures are slow and hidden until a stain appears inside.
You may not own a church tower, but the same principle applies to a Georgian or Victorian house with a parapet along the front, or to a shop with a stone coping at the roofline. Our lead roofing hub shows how new lead is laid, with falls, drips and laps formed so the sheet can expand and contract without tearing.
Stone parts need attention too. The coping stones on top of a parapet shed water to either side, and the joints between them open with age. The pointing behind and between them is where lime mortar is the right material, because it moves a little and lets moisture escape. Hard cement does the opposite and can damage the stone.
Reaching the work is the other half. A tower or a high parapet cannot be reached from a ladder. It needs scaffold, a mobile platform or a roof ladder fixed to a safe point, and the cost of that goes into the price from the start. If the building is listed, a consent application to Somerset Council comes before anything is erected against the stone.



