Roofing for the terraces of Wood Green and Noel Park, London N22
Where the rain goes
A shower on a Wood Green terrace takes the same road every time: down the slates, round the chimney, along a valley or a parapet gutter, out through an outlet and down a pipe. Urban Roofing Services works on the places along that road where a roof lets the water in.
A leak is found the way the rain finds it
A stain on a bedroom ceiling is rarely under the hole.
Water that gets past a roof runs along battens, rafters and the top of a wall before it shows, sometimes a metre or two from where it got in.
So the search starts at the ridge and follows the water down, junction by junction. This page runs in the same order: each stop below is a place where roofs in N22 commonly let water through, and what we do about it.
The slope
Slates keep water out by overlapping twice
A slate roof works because every point of it lies under two thicknesses of slate. Each course overlaps the course but one below it by the headlap, and what shows of each slate, the gauge, is half of what remains of its length once the headlap is taken off: a 500 millimetre slate at a 75 millimetre headlap shows 212.5.
Rain runs down the face of each slate and off its tail onto the next, never into a joint. That holds only while every slate stays where it was nailed. When a nail rusts through or a slate cracks, the slate slides, the course opens and water reaches the battens and the felt beneath.
We replace slipped, cracked and missing slates like for like, holding a single slate with a tingle, a strip of lead or copper, where the slate above stops a nail. When a whole slope has reached that point it is stripped, the sound slates kept, and re-covered on new underlay and battens to BS 5534, with the ridge and hips fixed mechanically.
The chimney
A stack is where the slope runs into a wall
A chimney interrupts the slope, and each side of it needs its own lead. Downhill, an apron is dressed over the slates. Along the sides, soakers are slipped between the courses and step flashings are tucked into the mortar joints above them. Uphill, where everything running down the slope arrives at the brickwork with nowhere to go, a back gutter turns the water aside.
That back gutter is where a stack most often leaks: leaves settle in it, a split opens where the lead was fixed too tightly to move, or its laps are too short for the pitch. The stain shows beside the chimney breast in the room below, often well down the wall.
We renew aprons, steps, soakers and back gutters in rolled lead, Code 4 for flashings and Code 5 for the apron and gutter, repoint, re-bed the flaunching and cap redundant pots with ventilation. Taking a stack down touches the party wall and building control, and those questions are settled first.
Valleys and parapet gutters
Some gutters carry a whole slope's water, out of sight
Where two slopes meet, both drain into the angle between them. Behind the front wall of a terrace the water runs into a box gutter the parapet hides from the street.
In the older London roof, two slopes falling inward to a central valley, the water crosses the whole house before it finds a way out. These gutters fail out of sight: lead in lengths too long to move cracks, a joint without a drip lets water sit in the lap, and an outlet packed with leaves lets the gutter fill until it rises over its upstand into the wall.
Valley and parapet gutters are relaid in rolled lead in bays short enough to move, each bay stepping down over the next at a drip so the water keeps falling toward the outlet. The outlet and the hopper below it are looked at on the same visit. Where a gutter straddles two houses, the neighbour's half belongs to the same repair.
The flat roof at the back
A flat roof needs a fall you can measure
The back additions, kitchen extensions and dormers on these terraces are mostly flat, and a flat roof is only flat to the eye. BS 6229 asks for a finished fall of at least 1 in 80 toward the outlet and recommends designing at 1 in 40, so tolerances and settling timbers still leave the water running.
We build the fall in with tapered firrings, cover in EPDM, GRP or a reinforced bitumen membrane, turn the membrane up the walls under a flashing, and size the outlet to the area it drains. Where fire risk cannot be ruled out no torch is used, following the Safe2Torch approach.
Outlet, hopper, pipe
Then out, and down the pipe
Everything a roof collects leaves through a few small openings: an outlet in the parapet, a hopper head on the wall, a gutter along the eaves and the downpipes below them. A packed hopper or a cracked joint sends a whole roof's water down the face of the brickwork, into the wall it was meant to protect.
On every job the gutters, outlets, hoppers and pipes that the water reaches are cleared, re-hung where they sag and run through with water before the scaffold comes down, cast iron or plastic to match the house. Fascias, soffits and bargeboards are put right on the same visit, because a gutter hangs only as true as the timber behind it.
Every job begins with a look at the roof itself.
How a job starts
- BookPick a half-day, tell us the street and the roof, where the water shows and when, and add a photo of the stain if you have one. Say whether the roof is shared.
- LookWe survey from the street, the loft and, where it is safe, a roof ladder or a tower, and photograph every part of the roof. The leak is traced to a junction, not guessed at.
- ScopeYou get the findings in writing with the photographs, and an itemised method: what is to be done, in which materials, from what access, and how anything found once the roof is open is reported to you before any extra work.
Some work needs permission first, and the survey says which: a Haringey licence for a scaffold on the pavement, building control for re-covering more than half a roof or putting on a heavier covering, the owners' notices for a party wall or a shared stack, and a word with the council before any change of material in the Noel Park conservation area.