How to quote for a loft conversion

A loft conversion is a deceptively big job dressed up as a room in the roof. It pulls in structure, every trade in the building, building control and regulations, and a pile of things you genuinely can't see until you open the roof up. Quote it as one tidy number and you're carrying every unknown on the build yourself. The trades who do this well stage it, price the certain parts firmly and handle the unknowns honestly. Here is how to structure a quote for a job this size so it protects your margin and the customer trusts it.

Know it's a multi-trade job before you price

A loft conversion is rarely one trade. By the time it's finished it's pulled in structural work, carpentry, a staircase, plumbing and electrics for a new room or en-suite, plastering, insulation, windows or dormers and decoration. Be clear on the quote which parts you're doing yourself and which need other trades, and either price their work into your figure or state plainly it's excluded and arranged separately. The biggest disputes come from a customer assuming the wiring, the en-suite or the staircase was in your price when it wasn't.

Account for the structure and building control

A loft conversion is structural work and it has to be done to the regulations, so that belongs in the quote, not as a surprise on the day. The roof structure usually needs altering, the new floor has to carry the load of a habitable room, and there are requirements around fire safety, escape, insulation and head height. That means structural calculations, building control involvement and inspections through the build. Build in what the job genuinely needs and explain why it's there. It protects the customer and it keeps the conversion legal and signed off, which is the whole point of doing it properly.

Don't underprice the staircase and access

The staircase is one of the most commonly underestimated parts of a loft conversion. It has to meet the regulations for a habitable room, it eats into the floor below, and fitting it often means reworking the landing, a wall or a bedroom underneath. It's not a ladder into a hatch. Survey where it lands, what it disrupts on the floor below, and factor that into both the price and the disruption you warn the customer about.

Stage the job

A loft conversion quotes cleanly when you break it into the stages of the build. It lets the customer follow the money, ties your payments to milestones, and stops anything getting forgotten across a long job.

• Structure: roof alterations, steels and beams, the new floor structure and any dormer framing.
• Weathertight: dormers, windows or rooflights, and making the new structure watertight.
• Staircase and access: forming the opening, fitting the stairs and reworking the floor below.
• First fix: plumbing and electrics for the room and any en-suite, plus insulation.
• Plastering and finishes: boarding, plastering, screed and drying-out time.
• Second fix: bathroom, electrics, doors, skirting and decoration, then making good and a clean.

Handle what you can't see until you open it up

The honest difficulty with a loft is what's hidden until you start. You won't know the true state of the existing roof timbers, the wall heads or what's behind the plaster below until you open up. Don't quote a fixed price as if everything is sound and then absorb the cost when it isn't. Quote the measurable, drawn work firmly, treat the genuine unknowns as a stated allowance or an estimate, and agree plainly that anything uncovered when you open up is priced and signed off before you carry on. This is exactly the line between a fixed quote and an estimate, and on a job this size it matters.

Price your own labour and materials, and tie payments to stages

Price your labour from the realistic programme across every stage, and your materials from your suppliers and the drawings, plus the trades you're bringing in. Price your own materials and labour for the conversion in front of you, because two lofts of the same footprint can be wildly different jobs depending on the roof structure, the staircase position and the spec. On a job this size, don't take one big deposit and the balance at the end. Tie payments to the stages so your cash flow matches the work and the customer pays for progress they can see.

Be clear about scope, exclusions and the unknowns

Set out the scope stage by stage, list any provisional sums for undecided finishes, and be explicit about exclusions: planning fees, building control fees, structural calculations, party wall matters or anything the customer is arranging themselves. State your stage payment schedule and what triggers each one. Most of all, be honest about the unknowns up front, because a customer who understands from day one that the roof timbers are a risk will take a fair extra far better than one who was promised a fixed price for everything.

For the standard sections every quote should carry, see what every professional quote should include. And because so much of a loft is hidden until you open up, our guide on quote vs estimate explains exactly where to commit to a fixed price and where to estimate.