Roofer and builder: who does what on your home?

When customers ask me whether a roofer or a builder should handle their project, I tell them straight: a builder makes the structure; I make it waterproof and keep it that way. On most jobs, the builder frames walls, sets steels, builds parapets and forms openings. I design and install the roofing system, the flashings and the drainage details that stop water getting in. If those two roles overlap or get muddled, you pay for it later in leaks, damp and arguments.

In my 18 years on the roof, I’ve noticed that the failures I’m called to fix nearly always happen at the join between the builder’s work and the roof. That’s why I prefer to be involved early, agree the details up front and take responsibility for all waterproofing. It keeps your timeline clean, your budget steady and your home dry.

Where a builder stops and I start

Typical builder scope

  • Foundations, walls, steels, joists and roof deck framing
  • Parapet walls, chimney rebuilds, dormer frames and sills
  • Openings for rooflights, doors and lanterns (to agreed sizes)

My roofing scope

  • Roof design details: falls, warm/cold build-ups, VCL, insulation and outlets
  • Waterproofing membranes (felt systems), trims and edge terminations
  • All flashings at walls, chimneys, abutments and roof windows
  • Integration with gutters, fascias, downpipes and rainwater goods
  • Testing, sign-off, warranties and photo documentation

Here’s my honest advice: let the builder form the structure and let me own every waterproofing detail. One person accountable for a watertight envelope prevents finger-pointing later.

The interface details that make or break a job

1) Flashings and cavity trays at abutments

Anywhere the roof meets brickwork needs proper step or chase flashings and, on new work, cavity trays above. I design the flashing heights, chase depths and lap lengths so rain and wind can’t push water inside. If you need specialist help, I also handle professional lead flashing installations to tie the roof into masonry safely.

2) Parapets and felt capping

Parapet walls look tidy but they are leak-prone if they aren’t capped and dressed correctly. I set the upstand heights, specify drips on both sides and finish with robust felt capping or metal trims. If you’re planning a parapet on an extension, ask me to review the drawings before any brickwork is built.

3) Insulation, VCL and condensation control

Warm roof, cold roof, hybrid – I’ll advise what suits your property. The key is continuity: the vapour control layer must be sealed; the insulation mustn’t be snaked around steels; and cold bridges must be eliminated. That’s the difference between a roof that stays dry inside and one that sweats and rots.

4) Falls, outlets and overflow strategy

Flat roofs aren’t flat. I design falls to at least 1:80 on the finished surface, specify outlets sized to your roof area and add secondary overflows where needed. I also plan where water goes in a downpour so it doesn’t end up in your neighbour’s garden or inside your soffits.

Planning an extension? Bring me in before the first block is laid

If you show me your drawings early, I’ll mark up the roof depths, insulation thickness, rooflight curb heights and flashing lines so your builder can frame to the right dimensions. It stops last‑minute compromises that cost time and money.

My pre-build roof checklist for your builder

  • Confirm structural falls or firrings for the designed gradient
  • Set deck height to allow for insulation, VCL, membrane and thresholds
  • Allow curb upstands (ideally 150 mm) at all abutments, doors and rooflights
  • Provide solid fixings for edge trims and handrails (if any)
  • Plan downpipe routes and future maintenance access

If your project is a rear addition, I’ve built a clear service page that explains my approach to sequencing, flashings and drainage on extensions. Have a read of my rear extension flat roof guide and then send me your plan set – I’ll talk you through the details.

How I sequence work with your builder

Typical order of works that keeps things moving

  • Builder completes walls, steels and roof joists to my set-out
  • Decking and falls formed, openings boxed, curb heights confirmed
  • I install VCL, insulation, waterproofing and trims
  • I fit flashings, outlets, sumps and test drainage
  • Builder finishes cladding and render to my finished levels

I coordinate dates directly with you and your builder. Through my client portal, you can track the schedule, see daily photo logs and download invoices and warranties without chasing.

Scaffolding, access and safety – who handles what?

On small roofs I often bring my own access; on bigger jobs and anything over conservatories or tight side returns, you’ll need scaffold. To help you budget, I provide a simple scaffolding price calculator. If you prefer, I can arrange scaffold as part of my fixed quote so there’s just one point of contact.

Loft conversions and dormers: builder vs roofer roles

On dormers, the builder frames, insulates the cheeks and installs windows. I handle the roof waterproofing, abutment flashings and the tricky junctions where the dormer meets the existing roof. If you’re planning a conversion, see my flat roof dormer guide for insulation options, curb heights and long‑term maintenance tips.

Repairs after a builder “has a go” at roofing

I get called to fix leaks from well-meaning builders who used the wrong adhesives, short laps or low upstands. It happens. If you ask me, I’ll tell you straight: it’s usually faster and cheaper to redo the affected area properly than to chase patches. I’ll diagnose the cause, explain your options and price the fix clearly so you can make a sensible decision.

Who should you call first?

If you’re extending or converting, speak to your builder and me at the same time. I’ll protect the roofline details while the builder plans structure and finishes. If you’re unsure what state your existing roof is in, book a free roof inspection and I’ll give you a realistic plan.

Fixed-price quotes, zero surprises

I use instant online estimating to help you budget, then I visit, measure properly and give you a fixed-price quote. No hidden extras, no vague day rates. Through my portal, you can see progress photos every day, so you know exactly what I’ve uncovered and how I’ve solved it.

If you’re comparing a roofer and a builder for the same task

  • Anything to do with waterproofing, flashings, membranes or gutters: call me
  • Structural framing, steels, brickwork, render and plaster: that’s the builder
  • Shared details (like abutments): I’ll specify them and either install myself or coordinate clearly

When customers ask me about saving money by letting the builder “do the roof”, I’ll be honest: sometimes it works; often it doesn’t. A roof is a system. If one detail is wrong, water will find it. My job is to think like water and stay a step ahead.

Next steps

I personally manage every project from the first estimate to the final handover. If you want a roof that’s designed once, installed right and documented properly, give me a call and let’s get your build moving the right way.