Most leaks on a terrace come from a handful of junctions, the places where one part of a roof hands its water to the next.
Read from the top of the roof to the bottom
Each junction below says how it usually fails, what an owner tends to see from inside the house, and what putting it right involves. The order is the order the water meets them, and a survey works through them in the same order, because the stain in a room is the end of a path, not its start. Turrets and bay roofs, which Noel Park's corner houses carry, are covered in the same way as the slopes: they are slated, flashed and drained like any other part of the roof, only in a tighter space.
Ridge and hips
It fails when
the mortar bedding under the ridge and hip tiles cracks and lets go, and the tiles lift or slide in a strong wind.
From inside
damp along the top of the loft, or daylight where the two slopes meet.
What we do
re-fix ridge and hip tiles mechanically, as BS 5534 has required since 2014, using a dry-fix system to BS 8612 where it suits the roof rather than relying on mortar alone.
The slate courses
It fails when
nails corrode and slates slip, or slates crack and split along their grain, and the double lap that keeps the water out is broken.
From inside
a damp patch part-way down the slope, wet battens, or a slate lying in the gutter after wind.
What we do
replace slates like for like, held with tingles where the course above stops a nail; re-cover the slope once the fixings have failed across it, saving the sound slates.
The chimney stack
It fails when
the back gutter fills with leaves or splits, flashings come out of their joints, or the flaunching on top cracks and lets water into the brickwork.
From inside
damp beside the chimney breast, often lower down the wall than the stack itself.
What we do
renew apron, soakers, step flashings and back gutter in rolled lead, repoint, re-bed the flaunching and cap redundant pots with ventilation.
The valley takes the water of both slopes at once.
Walls and dormers
It fails when
a roof meets a wall rising above it and the soakers or step flashings are missing, short or loose; dormer cheeks and tops wear through.
From inside
damp on the wall below the abutment, or stains round a dormer window.
What we do
interleave a soaker with every course under new step flashings, re-cover dormer cheeks and tops, and dress lead to sills and abutments.
Valleys and parapet gutters
It fails when
lead laid in long lengths cracks, a joint without a drip lets water sit in the lap, or a choked outlet lets the gutter fill and overtop.
From inside
a stain on the front bedroom ceiling, or damp on a party wall.
What we do
relay the gutter in bays with drips between them, and clear the outlet and the hopper it empties into on the same visit.
Flat roofs and their outlets
It fails when
the deck has too little fall or falls the wrong way, the membrane splits at an upstand, or the outlet blocks.
From inside
a ceiling stain in the kitchen extension or the back bedroom.
What we do
build the fall with firrings, cover in EPDM, GRP or reinforced bitumen, turn upstands under flashings, and work without a torch where fire risk cannot be ruled out. Old fibre-cement sheets are treated as containing asbestos until a test says otherwise.
Gutters and downpipes are the seventh place, and the one most often overlooked: a roof can be sound and its water still end up in the wall. They are part of every job, and run through with water before the scaffold comes down. If you can see one of these from the street or from inside, it is worth saying so when you book a survey; it tells us where to start looking.
