Every Question Answered

The simplest way is to book a free site survey via our website or by calling 07359 872594. Our specialist will visit your property, understand your brief, and provide a detailed, itemised estimate. For early-stage enquiries before you have drawings, we can provide a ballpark figure to help with budget planning.

For a detailed estimate: architectural drawings, structural engineer details (if available), your specification (finishes, bathroom suite, kitchen supplier), and the property address. For a ballpark figure: the type of project, rough size, and location. The more information you provide, the more accurate the figure.

No — but it helps. We can work with you from concept stage if you don't yet have drawings. On design-and-build projects, we coordinate the architect and structural engineer as part of our package. If you already have planning drawings or Building Regs drawings, bring those to the initial meeting.

Lead times vary by project size and time of year. Typically 4–10 weeks from appointment to start on site, depending on how quickly pre-construction (drawings, Planning/PD confirmation, Building Control, structural engineer) can be completed. We are transparent about our pipeline at point of enquiry.

Most loft conversions don't. Under Permitted Development, rear dormers and hip-to-gable conversions on houses (not flats) can proceed without a full planning application, provided the dormer is within volume limits (40m³ for terraces, 50m³ for semi-detached and detached). Mansard conversions almost always require planning. A Lawful Development Certificate is strongly recommended to document that PD applies.

Not always. A single-storey rear extension up to 4 metres deep (6 metres under the Prior Approval scheme) on a terraced or semi-detached house is within Permitted Development. Up to 8 metres on a detached house. Beyond these limits, full planning permission is required. In Conservation Areas, rules are stricter. We confirm the planning position on every project before work begins.

A Lawful Development Certificate (LDC) is a formal certificate issued by the council confirming your project is lawful without planning permission. It costs around £206 and takes 6–8 weeks. It is not mandatory but highly recommended — it proves to future solicitors and buyers that the work was legal. We recommend an LDC on every Permitted Development project.

A Householder Planning Application has an 8-week statutory target from validation to decision. In practice, many London councils take 10–14 weeks. Applications in Conservation Areas or those requiring additional consultation may take longer. Pre-application advice from the council can reduce this risk.

Probably, yes, if you are in a terraced or semi-detached house. Loft conversions commonly involve inserting beams into or adjacent to the party wall (triggering the Party Wall etc. Act 1996). Extensions within 3 metres of a neighbour's foundations also trigger the Act. We advise on party wall matters at the pre-construction stage and can recommend surveyors.

A Velux/rooflight conversion costs from around £18,000–£30,000. A rear dormer loft conversion (the most common type in London) ranges from £35,000–£65,000. An L-shaped dormer costs £55,000–£85,000. A mansard conversion starts from £70,000. These are guide ranges — actual costs depend on specification, location, finishes, and associated works (en-suite, staircase, etc.).

A single-storey rear extension typically costs £45,000–£90,000. A side return extension costs £35,000–£65,000. A wraparound extension costs £65,000–£120,000. A double-storey extension starts from £80,000. These figures are for the build works — they do not include architect fees, planning fees, structural engineer fees, or kitchen supply.

All quotes are provided exclusive of VAT and VAT is then added separately. The standard rate of VAT (20%) applies to most construction works. Some specific categories (e.g., conversion of a non-residential building to residential) are zero-rated — we will advise on the correct VAT treatment for your specific project.

A typical payment schedule for a loft conversion or extension: deposit on signing (10–15%), mobilisation and structural shell stage (30–35%), first-fix completion (25%), second-fix and practical completion (20–25%), final retention released after defects period (2.5–5%). We do not request large payments before work starts.

We supply all first-fix materials (structural, roofing, insulation, first-fix plumbing and electrical). Second-fix materials are client-supplied — this means: tiles, sanitaryware (bathroom suite, taps, shower enclosure), kitchen units and appliances, light fittings, door handles, floor finishes. We provide labour to install client-supplied items. We do not supply or install carpet.

A Velux conversion takes 5–7 weeks on site. A rear dormer loft conversion takes 8–12 weeks. An L-shaped dormer or hip-to-gable takes 10–14 weeks. A mansard conversion takes 14–20 weeks. These are on-site durations — pre-construction (drawings, Building Control, structural engineer) adds 8–12 weeks before site work starts.

For most loft conversions, no. The most disruptive stage is the 5–10 day period when the roof structure is exposed before the dormer is weathertight. Our teams work quickly through this stage with temporary weatherproofing in place. Most clients stay in the property throughout.

We manage all Building Control bookings as part of the project programme. You do not need to liaise with Building Control directly. We use either the local council's Building Control department or an Approved Inspector (private). A Completion Certificate is issued at the end of the project — we ensure this is obtained and passed to you.

Under CDM 2015 (Construction Design and Management Regulations), a Principal Contractor is the contractor responsible for planning, managing, and coordinating health and safety during the construction phase. RCB acts as Principal Contractor on all projects — this means you, as the client, transfer CDM responsibilities to us when you appoint us in writing.

Any change to the agreed scope is treated as a variation. We will price all variations in writing and obtain your written approval before carrying out additional work. We will never carry out additional work and invoice for it at the end without prior approval. The variation procedure is included in our contract.

We provide a 25-year structural warranty on all structural works (loft conversions, extensions, structural alterations). The warranty is issued in writing as part of the appointment. It covers structural defects arising from workmanship or materials. Manufacturer warranties apply to all installed products (e.g., windows, boilers, roof windows).

We operate a 12-month defects liability period after practical completion. Any defects that arise within 12 months arising from our workmanship are rectified at no additional charge. Call or email us and we will schedule a return visit. Beyond 12 months, the structural warranty covers structural defects.

Yes. Under CDM 2015, a Health and Safety File is produced and handed to you at project completion. It contains as-built drawings, structural calculations, product specifications, warranties, and location of hidden services. Keep it safely — it must be passed to future buyers of your property.

Yes. A significant portion of our work is for property investors, landlords, and developers. We understand the investment mindset — cost per square foot, rental yield, turnaround time, and specification appropriate to the tenant type or sale market. We offer portfolio pricing for multiple properties.

Yes. We have experience delivering HMO conversions in London. We understand the Building Regulations requirements (fire compartmentation, inter-tenancy wall sound insulation, fire alarm systems, emergency lighting, ventilation) and work with Housing Officers where licensing is required.

Yes. On some projects, clients prefer to manage their own labour supply while RCB provides Principal Contractor management, programme control, quality oversight, Building Control coordination, and CDM compliance. Contact us to discuss this arrangement.