AI tendering for roofers

A roofing tender is priced as a rate per square metre built from your gang's day cost, its real output and materials with waste, plus separate lines for edges, outlets, details and access. AI can measure the roof from the drawings and read the spec quickly. You still own the output rate, the wind and weather risk and the final number.

What makes roofing tenders hard to price?

Three things: the rate per m² hides most of the risk, the fixing spec changes with wind exposure, and the weather decides your programme. A main contractor compares your m² rate with three others and rarely reads the build-up.

Roofing subcontract packs tend to arrive as a roof plan, a few sections and a spec clause that names a system ("single-ply membrane, mechanically fastened, to manufacturer's wind uplift calculation"). The drawings show the area. They rarely show the condition of the existing deck, how materials get up to roof level, or who provides the edge protection.

On pitched roofs, the British Standard for slating and tiling, BS 5534, sets the fixing rules. Since its 2015 amendments, mortar can't be relied on as the only way of securing the roof covering, single-lap tiles and hip and ridge tiles must be mechanically fixed, and the standard includes a method for calculating fixing specifications from wind uplift. A tender that says "re-tile to match existing" without a fixing spec leaves you to work out how many clips and nails the roof needs, and to carry the cost if you guess low. See wind uplift and fixings for how the calculation works.

How do you price a flat roof tender from the drawings?

Measure the field area from the roof plan, price it per m² from your gang cost and output, then add perimeter trims, upstands, outlets and any extra fixings in the wind zones as separate lines. A single m² rate that tries to cover everything is how roofers end up either too dear or losing money.

Put the extras on their own lines because they move independently. Edges and outlets scale with the shape of the roof, not its area: a 420 m² roof cut into three levels has far more perimeter than one simple rectangle. If the main contractor asks for a single rate, work it out from these lines and keep the build-up.

Change the output first. Fifty m² a day for three people on a clear, flat deck with good access is a different job from 50 m² across five small roofs on a terrace.

Should you price this roof tender per m² or per day?

Per m² when the area is measurable and the work repeats; per day, or a fixed sum with stated days, when the work is mostly details, repairs or unknowns. The quick check below sorts most roofing enquiries.

If your rate is far off what the work goes for, the gap is usually in the output figure or in extras buried in the rate, so check those before cutting your margin. Converting a day rate to a price per m² shows the method in full.

What should a roofing tender qualify or exclude?

Access, the deck, weather, and every item "by others". Write them as you read the pack, tied to drawing and spec references, and put the biggest risk first.

Tender: project name, roofing package
Our price: £amount excluding VAT, dated date

1. Priced from roof plan drawing number and revision, sections numbers and specification clause reference.
2. Scaffold, edge protection and loading bays by the main contractor, in place and inspected before we start. Or: edge protection included as stated.
3. Hoisting of materials to roof level by others. Or: included using our hoist.
4. Skips and waste removal by the main contractor. Or: included, [number] skips.
5. Fixings to the manufacturer's site-specific wind uplift calculation, to be supplied before order. Changes to the fixing pattern after award will be valued as a variation.
6. Existing deck, timbers and battens assumed sound. Replacement priced at £rate per m² once exposed and agreed.
7. Roof covering only. Rooflights, rainwater goods below roof level, lightning protection and mansafe systems by others unless listed.
8. Price assumes continuous working in number visits. Work lost to rain, high wind or frost is not at our cost; programme to be extended accordingly.
9. Temporary weather protection at the end of each day included; protection of the building below beyond this is excluded.
10. Asbestos survey, removal and associated delays excluded.
11. Price valid for number days. Insulation and membrane prices are subject to supplier changes after that date.

For the general rules on wording, see tender qualifications and exclusions. A roofing schedule should be shorter than a builder's and more specific: the main contractor's estimator reads the access and weather lines first.

What can AI do on a roofing tender, and what can't it?

AI is useful for the reading and measuring; it's no use for judging the roof in front of you. Used well, it takes the evening out of a tender pack and leaves you with the decisions only you can make.

What it does well:

• Measuring areas from drawings. Roof plans with stated dimensions are a good fit. Pitched roofs need the pitch or a section to turn plan area into slope area, so check it used one. See testing an AI take-off.
• Coverage and quantities. Tiles per m², boards per roof, rolls of membrane, fixings per tile from the manufacturer's data.
• Spec clashes. A spec clause naming one system and a detail drawing showing another, or an adhesive that isn't approved for the insulation board.
• Drafting the qualifications. From your standard list, with the right drawing numbers in.

Check the coverage figures it used against the manufacturer's data sheet. A wrong coverage figure changes the whole order, which on a tender is the difference between winning at a loss and losing at a fair price.

What still needs you:

• The output rate. Only you know what your gang lays on a cut-up roof in November.
• The deck and the access. No drawing tells you whether the boards are rotten or the scaffold will be up on time.
• Weather risk. How much to allow for lost days is a judgement about the season, the site and the client.
• Sign-off. You approve the price and the qualifications. Nothing should go out without you reading it.

How do you win more roofing tenders without cutting the rate?

Bid the right ones, price them quickly and send a clean, specific submission. Read the pack for ten minutes before measuring anything, using the 10-minute tender read, and walk away from packs with no roof plan, no access arrangements and a fixed programme in winter.

A short, specific qualifications list makes your price comparable, which matters because main contractors normalise bids. A roofer who qualifies scaffold and states the fixing basis often ends up cheaper, after adjustment, than one with a lower headline rate and nothing written down. For how Nexley works for roofing firms more widely, see the roofing trade page.

Common questions