How to Write a Project Brief for a London Extension or Refurbishment: What to Include and Why It Matters

**What happens when there is no brief or a poor brief**:

Most London homeowners approaching a contractor for an extension or refurbishment start with a description along the lines of:

*'We want a kitchen extension at the back, open plan, with bi-fold doors to the garden, and maybe a new bathroom.'*

This is a description of the aspiration, not a project brief. The contractor pricing this description must make dozens of assumptions:

• •How big is the extension? (The price difference between 15m² and 30m² is £25,000–£40,000 on a standard London kitchen extension)
• •What is the ceiling height? (2.4m, 2.6m, or 2.8m — structural costs differ)
• •What type of flat roof — standard felt, GRP, EPDM, or green roof?
• •What size roof lantern, if any?
• •What specification of bi-fold doors — 3 panel, 4 panel; aluminium or timber; which colour?
• •What work is involved in the existing kitchen — full demolition of the existing rear room? Retention of any walls or services?
• •Is the wall between the existing kitchen and the new extension to be removed (structural opening, steel beam, temporary works)?
• •Does 'maybe a new bathroom' mean a new en-suite in the loft, a ground floor WC, or a new family bathroom?
• •What are the specification levels for tiles, sanitaryware, and fittings — are these client-supplied or included in the build price?
• •Are there planning constraints — permitted development or planning permission required?
• •Party wall issues with the neighbouring property?
• •What is the condition of the existing drainage — is a CCTV survey required before excavation?

Each of these unanswered questions creates a pricing assumption. Two contractors pricing the same vague brief will make different assumptions — their prices are then not directly comparable, which leads to the very common London experience of receiving three 'quotes' that vary by £40,000 and not understanding why.

**The brief as a level playing field**:

When all contractors pricing a project work from the same brief, their prices become genuinely comparable — differences reflect different overhead structures, margin expectations, subcontractor relationships, and procurement efficiency, not different interpretations of scope. This is both fairer to the contractors (who are competing on equal terms) and more useful to the homeowner (who can see why prices differ, rather than simply choosing the cheapest on the assumption that the scope is the same).

**The brief as a tool for better design decisions**:

Writing a project brief forces the homeowner to think through what they actually need (function) versus what they initially wanted (aspiration). Common examples:

• •A homeowner who wants bi-fold doors discovers, when writing the brief, that the main reason they want bi-folds is to open the extension to the garden — a sliding door achieves the same function at lower cost, which frees budget for better kitchen units or floor tiles
• •A homeowner who wants an open-plan kitchen/diner discovers that they need to specify whether the existing rear room is demolished completely (and the floor screed and drainage re-routed) or retained in part
• •A homeowner who wants 'more light' identifies, when writing the brief, that the main source of additional light is the roof lantern — and that the roof lantern size should be specified in the brief so it is priced by all contractors

**The brief as a variation prevention document**:

Variation costs (additional costs arising from scope changes after the project has started) are one of the largest sources of budget overrun on London residential projects. The majority of variations arise from:

• •Scope that was not defined in the original brief (the contractor included no allowance; the homeowner assumed it was included)
• •Design decisions that were deferred and then made during construction (when implementing the change is expensive)
• •Existing building conditions that were not surveyed or assessed before pricing (structural surprises; drainage surprises; asbestos; plumbing layout)

A clear brief does not prevent all variations — unforeseen existing conditions (the broken drain discovered in excavation; the asbestos found in floor tiles) are genuinely unforeseeable. But brief-driven variations (the homeowner decides mid-project to add a roof lantern; to move a door; to upgrade the floor tile) can be prevented almost entirely if the design decisions are made before construction starts.

**The eight sections of a construction project brief**:

*Section 1 — Property information*:

• •Full address of the property
• •Property type: Victorian terrace; 1930s semi; converted flat; purpose-built flat; etc.
• •Number of storeys; existing floor area (approximate)
• •Tenure: freehold; leasehold (and if leasehold, lease length and any freeholder restrictions on works)
• •Current condition: good condition, requiring cosmetic refresh only; mid-condition, requiring some redecoration and minor repairs as well as extension; poor condition, requiring significant structural or services upgrade as well as extension
• •Occupancy during works: will the property be occupied during the works, or vacated? (This affects programme, dust and protection requirements, welfare facilities, and working hours)

*Section 2 — What you want to achieve (the goal statement)*:

• A clear statement of the end goal, in functional terms:
• •*'We want to create an open-plan kitchen and living space at the rear of the house that connects to the garden, provides space for a dining table for 6–8 people, and replaces the existing dark, compartmentalised kitchen layout.'*
• •*'We want to convert the loft to create one additional double bedroom and a separate shower room, giving us a 4-bedroom property.'*
• •*'We want to refurbish the entire ground floor — strip out the existing kitchen, bathroom, and flooring, and provide a modern, contemporary finish throughout.'*

This goal statement tells the contractor and architect what success looks like — it is the reference point against which design proposals and scope are assessed.

*Section 3 — Scope of works (what needs to happen)*:

As specific as possible, listing what you know needs to happen:

• •Demolition and enabling works: which walls, floor finishes, or fittings are to be removed?
• •New structure: how many structural openings? What type of extension (single-storey rear; two-storey; loft conversion; side return)? What dimensions (length × width of extension footprint)?
• •Roof: flat roof (what type — EPDM, GRP, green roof?); roof lantern (what size?); pitched roof (what type of tiles?)
• •Windows and doors: bi-fold, sliding, single-door with side lights; dimensions; materials (aluminium, timber, uPVC); colour
• •First-fix plumbing: how many bathrooms, en-suites, or WCs to be created or refurbished? Is underfloor heating to be installed (electric or wet)? Is the boiler to be replaced?
• •First-fix electrical: how many new circuits (power, lighting, EV charger, underfloor heating)? Is a consumer unit replacement required? Is there smart home wiring?
• •Insulation and plastering: are walls, roof, and floors to be insulated to Part L standard? Any upgrade beyond minimum?
• •Second-fix: all second-fix materials to be client-supplied per RCB standard contract terms. Note any items where contractor supply is requested.
• •External works: patio, path, decking, fencing, drainage connections, dropped kerb?

*Section 4 — What you don't want included (exclusions)*:

• As important as what is included. Client-supplied items, works deferred to later, and scope that is explicitly not required:
• •*'Kitchen units, worktops, appliances, and taps are client-supplied and not included in the contractor's scope.'*
• •*'Floor tiles (to be client-supplied and installed by contractor) — the tile budget is £40/m²; installation labour is included in contractor scope.'*
• •*'Decorating is to be carried out by client's own decorator after practical completion.'*
• •*'Garden landscaping is not in scope — only the concrete base and drainage.'*

*Section 5 — Planning status and information available*:

• •Planning status: not yet applied; permitted development (LDC to be obtained); planning permission approved (attach a copy); planning permission pending
• •Architectural drawings: none yet; concept drawings only; planning drawings; full technical drawings
• •Structural engineer: not yet appointed; SE to be appointed; SE drawings available
• •Party wall: not yet assessed; party wall notices to be served; party wall award in place
• •Drainage: not yet surveyed; CCTV survey available; known drainage constraints
• •Other information: asbestos report; building survey; EPC; valuation

*Section 6 — Specification intent*:

• A clear description of the specification level intended — this sets the frame of reference for any allowance items:
• •*'Standard specification: functional and well-made, but mid-market finish. Floor tiles from a supplier such as Topps Tiles mid-range; sanitaryware from Ideal Standard or equivalent.'*
• •*'Mid-high specification: quality materials, some feature items. Porcelain large-format tiles; Villeroy & Boch or similar sanitaryware; quality aluminium bi-fold doors (Schüco or equivalent).'*
• •*'High specification: premium materials throughout. Bespoke joinery; natural stone; premium aluminium windows; underfloor heating throughout; smart home integration.'*

*Section 7 — Budget*:

The question homeowners most frequently resist answering — but the one that is most useful. Sharing a budget does not mean contractors price up to it — it means they can tell you whether what you want is achievable within your budget, or whether a value engineering conversation is needed before pricing begins. A budget range (e.g., *'Our construction budget is £80,000–£100,000, which we understand may not cover everything we've listed — we'd welcome a pre-pricing conversation about priorities'*) is more useful than no budget at all.

*Section 8 — Programme requirements*:

• •When do you want works to start? (Which month/quarter?)
• •Are there any hard deadlines? (Lease extension completing; baby due; school year; rental void expiry)
• •Are there any seasonal constraints? (Prefer not to start in November for a project likely to take 16+ weeks)
• •Occupancy during construction: if vacating, for how long?

**How a contractor uses the project brief**:

A well-written project brief allows a contractor to:

• •Understand the full scope before pricing — not assume
• •Identify which items are client-supplied vs. contractor-supplied
• •Identify what information is missing (no SE drawings, no drainage survey) and flag it as a pricing risk
• •Price genuinely comparable to other contractors pricing the same brief
• •Identify the qualification questions they need to answer (What is the existing ground condition? What is the drainage layout? Has the neighbouring property been notified?)
• •Produce an estimate with stated assumptions and exclusions that closely mirror the brief

At RCB, receiving a clear brief allows the estimating team to produce a more accurate, better-structured, and faster estimate — typically within 3–5 working days of site visit for a straightforward London extension, versus 5–7+ days when significant information is missing and assumptions must be documented and flagged.

**How an architect uses the project brief**:

An architect uses the project brief to develop concept design proposals. A clear brief — particularly the goal statement, the scope of works section, and the specification intent — allows the architect to produce design options that directly address the homeowner's objectives, rather than designing to their own aesthetic preferences. The brief also prevents the very common outcome of the architect producing a design that is beautiful but unbuildable within the homeowner's budget — because a brief that states the budget allows the architect to cost-check their design at concept stage.

**The brief-to-estimate workflow at RCB**:

1. Client completes brief (or discusses it with Faith during qualification call) 2. RCB reviews brief and identifies any missing information 3. Where significant information is missing, RCB requests documents or arranges a Google Meet to clarify before site visit 4. Site visit confirms existing conditions and any constraints not identified in the brief 5. Wil (lead estimator) prices the brief, with stated assumptions for any items not specified 6. Estimate issued with scope of works aligned to the brief 7. If estimate exceeds budget, value engineering discussion with client — brief updated; revised estimate issued

**Common brief gaps and how they affect pricing**:

• •*Missing drainage information*: contractor must allow for unknown drainage runs as a risk — typically adds £1,500–£3,000 as a contingency or provisional sum
• •*Missing structural information*: contractor cannot accurately price the structural steel without SE drawings — any structural allowance is provisional
• •*Unclear occupancy requirements*: significant impact on programme and logistics (hoarding; protection; waste management; working hours)
• •*Unknown specification level*: contractor must assume mid-market — if actual specification is higher, repricing is required
• •*Undisclosed planning status*: if planning permission has conditions (materials; drawings; no permitted development), the contractor needs to know before pricing

**The brief as a living document**:

The initial project brief is not the final specification — it is the starting point for the design and pre-construction process. As the project develops (architect produces drawings; SE produces calculations; drainage survey is completed), the brief is updated and refined into the formal scope of works and specification that forms the basis of the contract. The effort invested in the initial brief makes every subsequent stage faster, cheaper, and more accurate.