The Right Order of Works for a London Home Renovation or Extension

**Why sequencing matters in a London renovation**:

A London renovation is typically a complex sequence of interdependent activities — each trade or activity depends on the completion of the previous one, and the resources (materials, access, labour) for each must be coordinated carefully. Common sequencing errors and their consequences:

• •Plastering before first-fix plumbing and electrics: first-fix pipes and cables run through walls; if plastering is done first, the first-fix trades have to cut channels (chasing) through the fresh plaster — creating additional work, cost, and plaster dust damage
• •Floor screed before first-fix plumbing: UFH pipes need to be in the floor before the screed is poured; if screeding happens first, UFH cannot be installed without breaking up the screed
• •Decorating before second-fix: all painting is done after skirting boards, architraves, and door casings are installed; if decorating happens before these are fitted, the carpenter's work will mark the fresh paint
• •Roof finishes before drainage connections: rainwater from the new roof needs somewhere to go; if the downpipes and surface water drainage are not connected, the first heavy London rainstorm will flood the extension
• •Kitchen installation before floor tiling: floor tiles should be laid before the kitchen is installed (except for under-kick-board areas), because laying tiles around an installed kitchen is much harder and produces poorer results

**The correct order of works — stage by stage for a London rear extension with structural opening**:

• *Stage 1 — Site set-up and enabling works*:
• •Site establishment (hoarding, welfare unit, materials storage area)
• •Scaffold erection if required (for two-storey work or roof access)
• •Protection of existing finishes to be retained (floor protection, staircase protection, window and door protection)
• •Service diversions (gas, electric, water, drainage — where existing services run through the area to be demolished or where new connections require diversion)
• •Asbestos survey and removal (if the property was built before 2000 — always check before demolition)

• *Stage 2 — Demolition and enabling structural works*:
• •Demolition of existing structures (lean-to, outbuilding, paving in extension footprint)
• •Temporary propping of the existing rear wall (BEFORE the structural opening is made — a common error is to start making the opening before propping is in place)
• •Installation of temporary structural support (Acrow props, Strongboys, Acro steel — to SE's propping design)
• •Creation of structural opening (breaking out the load-bearing wall masonry to create the new opening)
• •Installation of structural beam (RSJ, UB, or other as per SE's design)
• •Installation of padstones (under beam bearings)
• •Removal of temporary propping (only after beam is fully installed and bedded in)

• *Stage 3 — Excavations and foundations*:
• •Excavation of extension footprint to foundation level
• •Building Control inspection of excavations (see `building-control-application-guide`)
• •Foundation concrete pour
• •Drain runs (foul and surface water) installed in the extension footprint BEFORE the floor build-up goes in — drainage runs cannot be installed retrospectively once the floor slab is poured
• •Building Control inspection of drainage (drain pressure test before backfill)

• *Stage 4 — Superstructure (walls and roof)*:
• •External wall construction (cavity walls or timber frame — rising from DPC level)
• •Building Control inspection at DPC level
• •Structural lintels and cavity trays over new openings
• •Window and bi-fold/sliding door frames installed (at frame-only stage — glass installed later)
• •Flat roof structural deck (OSB or concrete) installed
• •Flat roof insulation and waterproofing membrane installed
• •Rainwater gutters and downpipes connected to drainage (before the next rainfall)

• *Stage 5 — First-fix mechanical and electrical (M&E)*:
• •First-fix electrics (cable runs in walls, ceiling void, floor void; consumer unit position)
• •First-fix plumbing (pipework runs for kitchen, bathroom, UFH; pressure test on plumbing before concealing)
• •UFH pipes laid in floor (before floor screed)
• •First-fix heating (pipes and radiator tails in walls if radiators are to be fitted)
• •Building Control inspection at first-fix stage for new circuits (Part P)

• *Stage 6 — Insulation, plastering, and boarding*:
• •Floor screed (sand-cement or anhydrite liquid screed) — AFTER first-fix plumbing is in floor
• •Plasterboard to ceilings and new stud walls
• •Plastering to all new masonry walls and ceilings
• •Plastering to existing walls affected by structural work (making good around new beam)

• *Stage 7 — Windows and external doors (final glazing)*:
• •Bi-fold or sliding door panel installation (frames installed at Stage 4; panels installed after plastering to avoid damage)
• •Window glazing (if frames were installed at Stage 4 with temporary protection)
• •VELUX rooflights (glazing installed after waterproofing is complete)

• *Stage 8 — Second-fix M&E*:
• •Second-fix electrics (sockets, switches, light fittings, consumer unit, smoke alarms)
• •Second-fix plumbing (tap fittings, waste fittings, toilet cisterns, radiators)
• •Commissioning and testing of all M&E systems (smoke alarms tested, UFH zones tested, extract fans tested)
• •Electrical installation certificate (NICEIC/NAPIT Part P certificate)

• *Stage 9 — Second-fix carpentry and joinery*:
• •Internal door frames and linings
• •Skirting boards and architraves
• •Staircase handrails and balustrades (for loft conversions)
• •Fitted kitchen carcasses and worktops (client-supplied)

• *Stage 10 — Floor finishes*:
• •Tile adhesive and tile laying (porcelain, natural stone) — before kitchen plinth installation
• •Engineered timber floor installation
• •LVT installation
• •Client-supplied floor finishes, if applicable

• *Stage 11 — Decoration*:
• •Painting: primer coat to all new plasterwork (allow to fully dry — minimum 2 weeks for new plaster); two coats of emulsion to walls; two coats of gloss or eggshell to woodwork
• •Silicone sealing: kitchen and bathroom silicone at all junctions (worktop to wall, bath/shower tray to wall)

• *Stage 12 — Snagging and handover*:
• •Commissioning of all M&E systems (heating, ventilation, extract fans, smoke alarms)
• •Snagging inspection (see `snagging-guide`)
• •Building Control final inspection (have all certificates ready — electrical, gas safe, drainage test, insulation data sheets)
• •Completion certificate issued by Building Control
• •Site clearance and handover to client

**The most expensive sequencing mistakes in London renovation projects**:

*1. Screeding before first-fix plumbing — the most common and costly error*:

If the floor screed is poured before the UFH pipes are laid (or before the drainage runs within the floor build-up are installed), the floor must be broken up retrospectively. Breaking up a newly laid screed costs £800–£2,000 (depending on area and screed thickness) — plus the lost time and the cost of re-screed. In a kitchen extension, this also means the kitchen installation is delayed while the floor is remediated.

The correct sequence is: first-fix plumbing completed and pressure-tested → drain runs within floor built-up installed → Building Control inspection → floor insulation → screed.

*2. Installing the kitchen before floor tiles — cosmetic but annoying*:

Tile laying in a kitchen is much easier and produces better results when done before the kitchen carcasses are installed (because the tiles can be laid to a consistent grid without having to cut around the units). When kitchen carcasses are fitted first, the tiler has to work around them, produces poorer cuts, and the kick-board reveals often show uneven tile edges.

The correct sequence is: kitchen floor tiles laid to full room size → kitchen carcasses and worktops installed → kitchen plinth fitted to cover tile edge.

*3. Plastering before the roof is watertight — a classic weather damage situation*:

New plaster is very sensitive to moisture. If plastering is done inside the extension before the roof is fully watertight — before the waterproofing membrane is installed, before gutters and downpipes are connected — a single rain event can soak the fresh plaster, causing it to delaminate, crack, or develop staining that is very difficult to correct.

The correct sequence is: roof membrane installed and roof watertight → gutters and downpipes connected → plastering can begin.

*4. Installing bi-fold doors before plastering is complete*:

Bi-fold and sliding door glazed panels are fragile during construction — the glass can be scratched or cracked by plaster tools, the frames can be damaged by scaffold boards, and the track can be distorted by wall settlement during plastering. Installing the frames at the structural stage (Stage 4) and glazing only after plastering is complete (Stage 7) protects the expensive door system.

*5. Decorating before second-fix carpentry*:

Skirting boards and architraves are installed after plastering and before decoration. If the walls are painted before the carpenter fits the skirtings, the skirting fixing process (nailing or screwing through into the wall) will mark or crack the fresh paint, and gaps between the skirting and the wall (requiring silicone or caulk and touch-up painting) will be more difficult to achieve cleanly.

The correct sequence is: skirting boards and architraves installed and filled → primer and first coat of paint → final filler and preparation → final topcoat.

**Sequencing for a loft conversion — specific additional considerations**:

A loft conversion has a specific early sequencing requirement that differs from an extension:

*Loft conversion sequence priority — roof before floors*:

A loft conversion involves converting the existing roof void into habitable space. The first structural priority is to make the roof weathertight with the new structure in place — the dormer, new roof windows, and any structural changes to the roof must be completed and waterproofed before internal loft conversion work begins. Trying to do internal loft work (new floor joists, staircase, insulation) while the roof is open to the weather leads to water damage, structural swelling in new timber, and programme chaos.

Loft conversion sequence: structural propping → dormer construction (structure, cheeks, roof) → Velux rooflight installation → dormer waterproofing → new floor joists installed → new staircase opening formed → staircase installed → internal first-fix → internal plastering.

*Staircase access from first floor*:

For a loft conversion, the new staircase to the loft is typically formed by cutting an opening in the first floor ceiling and floor structure and constructing a new stair flight. This opening must be formed and the temporary access (ladders or temporary stair) managed safely throughout the project. The permanent staircase should be installed as early as practical (after the structural opening is formed and the new loft floor is installed) — a contractor working up and down a ladder for the entire project duration is both dangerous and slow.

**Building a programme — what a realistic London extension takes**:

The overall duration of a London rear extension project depends on the size, complexity, and number of trades involved. Indicative programme lengths:

| Project type | Typical on-site duration | |---|---| | Small single-storey rear extension (<15m², no structural opening) | 6–10 weeks | | Standard rear kitchen extension (20–30m², structural opening) | 10–16 weeks | | Wrap-around extension | 16–24 weeks | | Standard loft conversion (dormer, 1 bed + 1 bath) | 10–16 weeks | | Loft conversion + rear extension combined | 20–30 weeks | | Full house refurbishment | 16–32 weeks | | Basement conversion | 24–40 weeks |

These durations assume continuous work by a competent team and exclude pre-construction time (planning, Building Regulations approval, procurement). They are highly dependent on the quality of the programme management and the availability of specialist trades.

**The role of the principal contractor in managing the sequence**:

The principal contractor is responsible for coordinating the programme and managing the sequence of trades. This is one of the most important functions of the PC role — more valuable on complex multi-trade projects (extensions, loft conversions, refurbishments) than on single-trade work.

• A principal contractor who manages the sequence well:
• •Has all trades booked in sequence before work starts (not ringing round for an electrician when the plastering is nearly done)
• •Ensures preceding works are complete before the next trade mobilises (no tiler on site when the screed is still green)
• •Manages material lead times (steel beams, bespoke windows and doors, structural timber) so they arrive on site when needed — not 3 weeks late
• •Communicates with the homeowner about sequence and programme (so the homeowner knows when they need to make decisions, when client-supplied materials need to be on site, and when Building Control inspections are scheduled)
• •Manages the interface between trades (who is responsible for making good after first-fix trades before plastering, who removes plasterboard offcuts, who is responsible for protecting floors between trades)

**Material lead times that affect the programme**:

Several materials and products have significant lead times that must be incorporated into the programme — not left until they are needed on site:

• •*Structural steel beams*: Fabricated to SE's design — typically 3–5 weeks from order
• •*Bi-fold or sliding door systems* (good-quality aluminium): 4–10 weeks from order to delivery; some manufacturers 12–16 weeks for bespoke sizes
• •*Velux rooflights (standard sizes)*: Usually available from builders' merchants within 1–2 weeks; bespoke/non-standard sizes: 6–10 weeks
• •*Bespoke windows* (timber, special sizes): 6–12 weeks
• •*Kitchen units* (bespoke or semi-bespoke from manufacturers like Howdens, Magnet): 2–8 weeks from order; fully bespoke hand-painted kitchens 12–20 weeks
• •*Natural stone floor tiles* (imported Carrara marble, travertine, etc.): 3–8 weeks from order; if material is not in UK stock
• •*Clay roof tiles to match existing* (for rear extensions where the roof slope is to match the existing): check availability — some traditional London clay tiles are not in current production; allow 4–8 weeks to source from reclamation yards

Poor management of material lead times is one of the most common causes of programme delays in London residential renovation projects — a two-week programme slip caused by bi-fold doors arriving late is avoidable with good procurement planning.