Terms and conditions for a loft conversion and extension builder

A loft conversion or a rear extension is the largest single purchase most of your customers will ever make from a trade, and it happens while they are living in the house. Your terms need to deal with steels, provisional sums, party wall delays, building control sign-off and a final payment that lands months after the deposit. I draft those terms for a fixed fee of £995, delivered in five working days.

Who this is for

Loft conversion specialists, extension builders and design and build contractors in England and Wales, trading as a sole trader, a partnership or a limited company. Most of your customers are homeowners and are consumers in law. Some work comes from developers, landlords and letting agents, who are business customers with different rules on payment and liability. One set of terms should handle both.

What matters in a loft and extension builder's terms

Drawings, design responsibility and permissions

Most loft and extension work is built to somebody else's drawings: an architect's plans and a structural engineer's calculations for the steels. Your terms should say plainly whether you are pricing a build only contract or taking design responsibility, because those are different risks and usually different insurance. They should also put planning permission, permitted development confirmation and the accuracy of the drawings on the customer, and set out what happens when the drawings and the existing building disagree, which on a Victorian roof they usually do.

Provisional sums and what opening up reveals

A price for a loft is built on assumptions about what sits behind the plaster. Undersized foundations, rotten wall plates, a chimney breast someone removed without support, asbestos in the artex, wiring that will not pass inspection: none of that is visible when you quote. The terms need a mechanism that names your assumptions, prices provisional sums as provisional, and requires any extra to be agreed in writing, with its effect on the programme, before you carry on. Agreements made verbally on a scaffold are where the final invoice argument begins.

Deposits, cancellation and the fourteen day period

These contracts are usually signed at the customer's kitchen table or agreed by email, which brings them within the Consumer Contracts (Information, Cancellation and Additional Charges) Regulations 2013. A homeowner has fourteen days to cancel. On a job where you order steels and book scaffolding in the first week, that matters: if you start inside the period without the customer's express request you may not be paid for the work, and missing cancellation information can extend the period by up to 12 months. Your terms and your ordering process have to work together.

Stage payments, retention and the final invoice

Price the job in stages tied to events you control: deposit on order, payment when the steels are in, when the structure is watertight, at plaster, and the balance on completion. Say what triggers each stage and how long the customer has to pay. Homeowners often ask to hold money back until the completion certificate arrives; if you agree, fix the sum and fix the release date. For developers and other business customers the Late Payment of Commercial Debts (Interest) Act 1998 gives you interest and fixed compensation, and your terms should not accidentally give that up.

An occupied house, scaffolding and the neighbours

The customer is living there while you cut a hole in their roof. The terms should cover working hours, access and keys, use of water and power, where materials and skips go, protection of existing finishes, and the dust and disruption that no amount of sheeting prevents. Party wall notices are the homeowner's responsibility as building owner, and so is any surveyor's award, scaffold licence or oversail agreement. Say that delay caused by waiting for those, or by a neighbour's objection, extends your programme and is not your liability.

Weather, insurance, building control and defects

While the roof is open the existing house is exposed, and water damage to the rooms below is the most expensive dispute in this trade. The terms should set out your temporary weatherproofing obligations and confirm who insures the existing structure and the works in progress. Structural work here must be notified or certified under the Building Regulations and sign-off depends on an inspector, so completion dates should be estimates. Set a defects period and a snagging process, cap liability for business customers, and remember that the Consumer Rights Act 2015 sets a floor for homeowners you cannot contract below.

What it costs

Customer or supplier terms and conditions, £995. One set of terms, customer-facing or supplier-facing, drafted around your business. Five working days.

Review of your existing terms, £495. You already have terms and want to know how much of a problem they are. Returned marked up with my amendments and an explanation of the changes. Three working days.

Buying online forms the engagement on payment. The scope is what the terms and conditions drafting page describes, you accept the Terms of Service at checkout, and I email you within four working hours to get started. If you would rather ask something first, email me.

What you get

• A full set of terms drafted around your business, not a template with your name inserted
• A covering note in plain English explaining every commercial choice I made and why, so you can defend the terms in a negotiation without ringing me
• Liability, payment, termination and IP provisions set at a level that will survive a procurement review
• Consumer-facing wording drafted to be enforceable where you sell to consumers
• Guidance on how to incorporate the terms properly, which is where most businesses actually fail
• One round of amendments after you have read them

What is not included

• Negotiating your terms with individual customers
• Sector-specific regulatory compliance beyond the contract terms themselves
• Website privacy notice and cookie compliance, which I quote separately
• Terms governed by the law of another country

Questions I am often asked

What if the party wall surveyor or building control holds the job up?

That belongs in an extension of time clause. Your terms should list the events that push the programme back, including waiting for a party wall award, an inspector's visit, a neighbour's objection or a decision the customer has not made, and treat dates as estimates. Without it, an overrun nobody controlled becomes your breach.

Do I need different terms when I build for a developer or a landlord?

One document can cover both if the consumer wording and the business wording are kept separate. Work for a developer or landlord who is not a residential occupier is caught by the Housing Grants, Construction and Regeneration Act 1996, which implies adjudication rights, payment notice rules and staged payments on longer contracts, and bans pay when paid.

The customer wants to hold money back until the completion certificate. Should I agree?

Plenty of builders do, and it can win the job. Agree it only in writing: a stated sum, a stated release date, and a right to be paid if certification is delayed for reasons that are not your fault. Open ended money held against a certificate issued by somebody else is money you may spend a year chasing.

Related guidance and services

• Terms and conditions drafting, £995, the service this page describes
• Contract review, £495
• Consultancy and contractor agreements, £595
• Terms and conditions for a builder doing domestic work
• Terms and conditions for a roofing business

This page is general guidance for businesses in England and Wales, not advice on your own circumstances. Last reviewed: September 2026. Email geoffrey@caesar.co.uk.