Planning permission granted? Excellent. The next phase turns drawings into a coordinated, build‑ready package your builder can price accurately and construct efficiently. This guide covers every step—from verifying existing information to tender, contracts, and snagging—plus helpful links to resources on detailed-planning.co.uk.
1) Confirm the Existing Information (and Whether It Needs Scanning)
Everything that follows relies on accurate base data. If existing drawings are approximate or outdated, expect rework and site surprises.
What to check
- As‑built accuracy: Do plans/elevations/sections match the house? Have previous alterations been captured?
- Levels & structure: Floor levels, ceiling heights, wall thicknesses, joist directions, roof build‑ups.
- Site constraints: Boundaries, trees/TPOs, access widths, external levels, outbuildings.
- Services: Incoming water, gas, electric, telecoms, drainage outfalls and manholes.
When to scan
- Complex geometry or poor records—3D laser scanning/point cloud avoids downstream clashes.
- Tight tolerances—slim‑frame doors and bespoke joinery need millimetre‑true openings.
- Hidden structure—targeted opening‑up to verify load paths and bearings.
Still exploring options? Start with Which house extension is right for you?
2) Drainage Surveys (Know Your Pipes Before You Dig)
Underground drainage affects layouts, floor levels, and foundation cost. Commission a CCTV drainage survey to confirm routes, sizes, depths, condition, and connections.
Why it matters
- Foundations: Drain runs may dictate pad positions or slab thickening.
- Build‑over: Shared/public sewers within ~3 m often require consent (see Section 8).
- Surface water: Decide early—soakaway versus combined sewer; check infiltration if considering soakaways.
3) SAP Calculations (Especially with Lots of Glazing)
Large glazed areas need correct glass spec and fabric performance to meet Part L. SAP balances U‑values, g‑values and thermal junctions against insulation and services.
- Confirm glazing spec (U/g values, spacers).
- Detail thermal bridges and airtightness strategy.
- Optimise fabric/services trade‑offs—high‑performance glass versus additional insulation or heat‑pump efficiency.
New to technical deliverables? See How to create planning drawings for a refresher on scaled documentation leading into approvals.
4) Structural Engineer’s Design (Beams, Pads, Load Paths)
The structural engineer sizes steels/RSJs, columns, pad foundations and connections once architectural intent is locked.
What you’ll receive
- GA drawings locating steels, padstones, bearings and lintels.
- Calculation pack for Building Control.
- Temporary works notes for safe sequencing and propping.
5) Building Regulation Drawings (The Technical Blueprint)
BR drawings coordinate structure, insulation, fire, ventilation, drainage and more—so the builder isn’t forced to “design on site”.
- Plans/sections/elevations with wall/roof/floor build‑ups and junction details (DPCs, cavity trays, thermal breaks).
- Compliance notes for Parts A, B, E, F, H, L, M (as applicable) and P via competent installers.
See our Building Regulations Drawings service to understand what’s included.
6) Building Control (Routes, Approvals, Inspections)
Appoint either Local Authority Building Control or a Registered Building Control Approver.
Routes
- Full Plans: Submit drawings + calcs for approval before start—fewer surprises.
- Building Notice: Faster but riskier on complex projects; design decisions shift to site.
Compare planning and building regs in our plain‑English guide: Planning Permission vs Building Regulations.
7) Neighbour Matters & Party Wall Agreements
Excavating near neighbours, building on/at the boundary, or cutting into a party wall (e.g., for new steel bearings) likely triggers the Party Wall etc. Act 1996. Appoint a party wall surveyor early.
8) Build‑Over Agreements (Shared/Public Sewers)
If a shared/public sewer is within ~3 m—or you plan to build over/near it—you’ll need water‑authority consent. Expect drainage drawings, CCTV evidence and structural protection details. Resolve before pouring foundations.
9) Optional (But Valuable) Additions
- Window & Door Schedules — sizes, types, opening directions, glass spec, finish, hardware, trickle vents, thresholds for like‑for‑like quotes.
- Electrical & Switching Plans — circuits, switching logic, socket heights, data/AV, external lighting.
- Schedule of Works (SoW) / Specification — inclusions/exclusions, standards, installation methods, finishes, responsibilities.
- Kitchen Design (with supplier) — lock layout early; confirm appliance specs, island size, extraction, power/water points.
Browse real outcomes in our recent projects.
10) Start the Tender Process (3–5 Comparable Quotes)
Issue the same coordinated pack to every bidder with a clear return date.
Due diligence
- Credentials: PL/EL insurance, H&S policies, accreditations.
- References: Speak to recent clients; view live/completed jobs.
- Programme & resourcing: Who runs your job? What’s their workload?
- Price clarity: Ask for a breakdown aligned to your SoW.
Quote review
- Normalise PC sums and provisional sums.
- Record exclusions (kitchen supply, flooring, specialist glazing) and assign risks.
- Choose best‑value, not just the lowest number.
Want a quick sense‑check? Book a call and we’ll review your pack/shortlist.
11) Prepare for Build (Make Site Ready)
- Decant & protection: Move valuables; agree dust routes and floor protection.
- Access & storage: Skips, deliveries, on‑street arrangements, welfare and security.
- Temporary services: Temporary water/ power; site WC.
- Neighbour comms: Share dates and a site contact; consider quiet hours/delivery windows.
12) Check Insurance (Home & Builder)
- Home insurance: Notify your provider; confirm cover for alterations/unoccupied periods.
- Builder’s insurance: Public liability, employer’s liability, contract works; PI if design elements exist.
- Certificates/Warranties: Gas Safe, NICEIC, glazing compliance, product warranties—keep a digital folder.
13) Services Review (Plumber/Electrician Upgrades)
- Heating & hot water capacity: Boiler/heat‑pump, cylinders, recovery times.
- Emitters & zones: UFH/radiators, manifold positions, controls.
- Ventilation: Trickle vents, extract rates, any MVHR/MEV—align with SAP.
- Water pressure: Consider a mains boost for multi‑shower homes.
14) Contractor Review & Intrusive Surveys
Invite the contractor to raise RFIs before start. Where assumptions remain—particularly around structure—carry out targeted opening‑up to confirm joist directions, wall types and bearings. Prevention beats redesign.
Why a coordinated technical pack matters? Read Architectural services vs design & build.
15) Sign the Contract
- Fixed price tied to drawings and SoW.
- Programme with start/finish dates.
- Payment schedule linked to milestones.
- Change control for pricing/approval of variations.
- Defects period for snag rectification post‑completion.
16) Pre‑Start Meeting & Kick‑Off
- Roles and communication lines (who signs what).
- Lead times for critical items (steels, windows, kitchen).
- Inspection stages (Building Control, build‑over).
- Site rules: hours, deliveries, waste, neighbour considerations, security.
17) During the Build: Keep Decisions Flowing
- Finishes/fixtures: Tiles, thresholds, ironmongery, paint systems.
- Unexpected finds: Old drains/steels—decide quickly using your contingency.
- Quality checks: Photograph concealed works (insulation, airtightness tapes, drainage) and compare with drawings/spec.
18) Snagging, Handover & Enjoy
At practical completion, compile a snag list (functional issues first). On handover, collect:
- As‑built drawings and O&M manuals.
- Certificates (electrical, gas, glazing, Building Control completion, water‑authority sign‑off).
- Warranties (retain digitally and in paper form).
Agree a reasonable defects period for seasonal shrinkage and minor adjustments—then enjoy the new space.
A Simple Checklist (Recap)
- Verify existing drawings; scan if accuracy is doubtful.
- Commission CCTV drainage survey and plan.
- Run SAP calcs for glazing‑heavy designs.
- Obtain structural engineer’s drawings + calcs.
- Produce coordinated Building Regulation drawings.
- Appoint Building Control; agree inspection stages.
- Address Party Wall matters early (serve notices if required).
- Apply for build‑over agreement where sewers are affected.
- Prepare optional schedules (windows/doors, electrics) and a detailed SoW.
- Tender to 3–5 builders; normalise and review quotes.
- Prepare the home and logistics for site start.
- Confirm insurance and warranty pathways.
- Hold services review; plan upgrades if needed.
- Resolve RFIs; carry out intrusive surveys to confirm assumptions.
- Sign a robust contract with clear payment and variation terms.
- Run a pre‑start meeting; issue minutes.
- Manage decisions during the build with short weekly check‑ins.
- Snag, collect certificates, close out—and enjoy.
