The evidence
Nine photographs, nine findings
Front elevation Context
Two-storey Victorian terrace with a two-storey bay to the front, a flat roof over the bay, a main pitched roof in concrete interlocking tiles, and a brick chimney stack shared with the neighbour. From the pavement the roof looked ordinary. Nothing below was visible without going up.
The survey was carried out from ladder and roof level, not from the street. Most of what follows cannot be seen from the ground, which is exactly why a homebuyer's survey missed it.
Bay window flat roof High
GRP (fibreglass) covering over the bay with a visibly thin, patchy laminate. Insufficient resin was used in the original application: the glass mat is exposed in places, the surface is chalky, and water was tracking through into the bay ceiling below.
A GRP roof relies on the mat being fully wetted out with resin; a starved laminate is porous. This roof cannot be patched reliably and needs a complete resurface.
Party-wall junction (front) High
Where the roof meets the neighbouring property, a strip of roofing felt has been used to bridge the two roofs instead of a proper bonding gutter. The felt has corroded, split and lifted, leaving the timbers below exposed.
A felt strip is not an acceptable detail at a party-wall junction. It does not provide the resistance to moisture required under Approved Document C of the Building Regulations and it was already letting water in.
Party-wall junction (detail) High
Close-up of the failed felt with the batten and the neighbour's slate roof beneath. Water has been running behind the felt and down the party wall line.
This is the single most serious defect on the roof. A secret (bonding) gutter formed in lead or GRP is the correct repair.
Slipped and fallen tiles Medium
Several tiles at the verge and near the ridge have slipped or come away entirely, exposing the underlay. Fragments of broken tile were lying loose on the roof surface.
Loose tiles are a safety risk as well as a leak risk. All displaced tiles need to be refixed with clips and nails; the fallen ones replaced.
Ridge line High
The mortar bed to the ridge tiles has failed along the full length of the ridge. Gaps are visible under the ridge tiles and broken mortar has fallen onto the roof slopes.
With the bed gone the ridge tiles are held by nothing but their own weight. In a gale they will come off. The ridges need lifting, all failed mortar removing, and re-bedding and re-pointing.
Ridge and hip detail High
Hollow, cracked bedding under the ridge with the tile beneath sitting proud. Moss is established in the open joints, holding water against the underlay.
Same defect, second location. The whole ridge run is affected, not an isolated section.
Chimney stack Medium
Brick chimney with eroded mortar joints on all visible faces, open joints below the corbelled brickwork and vegetation growing from the top courses.
Open joints allow water into the stack and, in winter, into the flue and chimney breast below. Full repointing is required.
Chimney flaunching Medium
The flaunching (the mortar cap on top of the stack) is heavily weathered, cracked and covered in moss and lichen, with a loose brick lying in it.
Failed flaunching lets water into the top of the stack and loosens the pots. It needs breaking off and replacing.