Roofers in Eastcott

The terraces on Bath Road have shallow pitched roofs in Welsh slate, and their low slope is part of their look. It is also what makes them fussy to repair. A slate that is perfectly adequate at a steep pitch can leak at a shallow one, simply because rain has longer to find a way through.

Q1.1How much overlap does a shallow slate need?

British Standard 5534 gives a minimum roof pitch for natural slate of 20 degrees, for a standard 500 mm slate in moderate exposure, with a 115 mm headlap. The headlap is the distance each slate overlaps the course two rows below it. As the roof gets steeper, the required headlap falls. Cupa Pizarras publishes the figures, and the table below shows them for a common slate size.

Q1.2What usually goes wrong on a low slope?

On a low-pitched roof, the usual faults are slipped slates, rusted nails and worn lead where the slope meets a wall. Replacement slate needs to match the originals in size and thickness, or the courses fall out of line. Reclaimed Welsh slate is often the best match, and we say where it has come from.

Q1.3How should the lead be laid on a low slope?

Where a shallow slope reaches a chimney, a shared wall or a valley, the lead has to stand higher and lap further than it would on a steep roof. Code 4 lead is the usual choice for general flashings, and heavier codes go into valleys and gutters. A flashing that was fitted generously a century and a half ago can still fail because the slate beside it has dropped and exposed the joint.

Q1.4Why photograph the roof first?

A shallow roof is hard to see from the ground. We photograph each slope closely, so you can see the individual faults and decide with us whether a repair or a re-lay is the better value. Our slate roofing page explains the process.

Replacing slate with a cheaper-looking tile is a decision that many owners consider when a quote for re-slating comes back high. It is worth understanding what the swap really involves before deciding.

Q3.1Is concrete tile too heavy for the rafters?

Concrete tile is heavier than natural slate. The Planning Portal says that a new covering that increases the weight of the roof covering by 15 per cent or more needs approval, and it advises a structural check. Approved Document A speaks of a significant change in loading as more than 15 per cent. A roof built for slate has rafters sized for slate, so we would look at the rafters and the purlins before agreeing to a heavier covering.

Q3.2How does a swapped roof look from the pavement?

The Old Town appraisal says that concrete tiles and reconstituted slates have detracted from some buildings. A terrace where one house has swapped its slate stands out from the others, and in a conservation area the council may well take an interest.

Q3.3What is the lower-risk option?

If the budget is the concern, a repair with matching slate often costs a fraction of a full re-roof, and a partial re-slate of the worst slope can be a middle course. Our tile-to-slate guide covers the reverse swap, which is sometimes the best way to restore a roof that was changed in the past.

Whichever way you lean, the written quote names the course we recommend and gives the reason for it. Small repairs are covered by our roof repairs work, and where re-slating only the worst slope is the sounder choice, the quote says so instead of pushing for the whole roof.