The short answer
Use a specialist roofer when the job involves leadwork, slating, stone tiles, flat roof membranes, parapet or box gutters, or any roof on an older or listed building. A general builder is a sensible choice for work that is mostly building, such as an extension, where the roof is one part of a larger project. Even then, ask who will do the roofing and whether they have done this type before.
What the two trades actually do
A general builder takes on a wide range of work: walls, floors, openings, plastering and often a bit of roofing as part of a larger project. A roofer does one thing, day in and day out, and has the tools, the habits and the eye that come with it.
That difference shows in small ways. A roofer reads a roof the way a mechanic listens to an engine. They notice a sagging line at the eaves, the colour of a slate that is beginning to delaminate, or the bead of cement that someone has used where lime or lead should have gone. They know the right gauge for a particular slate, the right headlap for a particular exposure and the order in which the layers of a flashing must go in.
None of this means builders cannot roof. Many can, particularly on a plain modern pitched roof with concrete tiles. The real question is whether your roof is plain, and whether you want the fitter learning on your house.
Jobs that really do need roofing skill
Some work is quite different from general building, and mistakes in it tend to show up as leaks a year or two later.
- Leadwork. Lead is used for flashings, valleys, gutters and flat sections. It must be cut, dressed and fixed so that heat and cold do not split it. Lead sheet comes in numbered codes by thickness, and the right code for the position matters. A parapet gutter runs along the foot of a wall that rises above the eaves. Setting its falls and drips correctly is a specialist job.
- Slating. A slate roof depends on correct gauge, headlap and fixings. Slate nailed too high, or with the wrong nails, may slip within a few years.
- Stone and clay tiles. These are heavy, uneven and fixed in a different pattern from machine-made tiles. Matching them to what is already there takes skill and a source of suitable material.
- Flat roofs. Membranes such as EPDM (synthetic rubber), GRP (glass-reinforced plastic) and lead each have their own preparation, laps and edge details. Falls to drain the roof, and neat upstands at the walls, are where flat roofs succeed or fail.
- Ridge, hip and verge work. Modern standards expect these to be mechanically fixed, not held by mortar alone.
If your roof has any of these, a specialist is the safer choice. Our note on roofing regulations in Bath explains why the paperwork side matters too.
Why it affects how long the work lasts
A roof fails first at its weakest detail, not across the whole slope. A slate that is sound will outlast the nail that holds it, and a lead flashing that is dressed correctly will outlast one that has been pinned to the wall with a bead of sealant. The skill in roofing is largely the skill of doing those details so that they last.
That is true on any roof, but it is especially true on an older one. Many traditional roofs were built with lime mortar, hand-cut slate and lead gutters, and they rely on the materials working together. Repairing them with the wrong material, such as hard cement mortar on soft stone or an unsuitable modern membrane on a roof that needs to breathe, can leave you worse off than the original fault.
A specialist is likely to recognise these traps. They also tend to quote for the hidden parts, such as new battens, underlay and lead, that a quick job leaves out. The result is a roof that is put right as it was built, not simply covered over.
When a builder is the right call
There are good reasons to use a builder. If you are building an extension, converting a loft or adding a storey, the roof is part of a larger structural project, and having one contractor responsible for it all can keep things simple. A good builder will bring in a roofer for the specialist parts, and you should ask openly who that will be.
A plain, accessible pitched roof with a modern covering and no complicated junctions is also within many builders' competence. If you decide to go that way, ask the builder the same questions you would put to any roofer: what the roof is made of, what will be replaced, how it will be fixed, what is covered by the guarantee and who will be on site.
It is worth asking whether the builder has worked on roofs like yours, and for a written quote that names the materials and the leadwork. If the answers are vague, that tells you something. The steps for vetting a roofer work equally well for a builder who offers to do your roof.
Questions to ask whoever you choose
Whether you pick a specialist or a generalist, a handful of questions will tell you much of what you need.
- Have you worked on this type of roof before, and can you describe a similar job?
- Who will actually do the work on my roof, your own people or subcontractors?
- What will you replace and what will you reuse, and how will the lead be handled?
- Will the work need Building Regulations approval, and who deals with it?
- How will you keep the house dry if rain arrives with the roof open? The page on wet weather on site describes a good answer.
- What guarantee do you give, and is it in writing?
Then compare the answers across firms. Collecting three or so quotes lets you set them side by side and compare like with like.
Roofing is our only trade. We look at the roof, explain what is wrong and put a fixed price on paper, and on a listed or conservation area building we say clearly which permissions apply. Someone else's quote for your roof can be sent to us through the home page for a second opinion.
