"How long will it take?" decides more insulation projects than the price does — because time on site is disruption, and disruption is what people actually fear. The durations below are typical ranges from our own completed jobs — 500+ installations across London and the South-East — organised by measure, plus the honest answer on how long you wait between enquiring and a crew arriving.
Durations at a glance
| Measure | Typical duration | Crew on site |
|---|---|---|
| Loft top-up | Usually a day | Inside the loft only |
| Suspended floor | A few days | Room by room, or from below |
| IWI | Roughly a week per few rooms | One sealed room at a time |
| Whole-house EWI | Several weeks incl. scaffold | Outside, on scaffold |
These are working patterns, not promises — the honest variables are covered below. But the shape is reliable: the internal "quick win" measures are measured in days; wall insulation is measured in weeks.
Loft and floor: the day-scale jobs
Loft top-up: usually a day
Rolling new mineral wool over an existing thin layer is the fastest measure in the book — our 40m² top-up in Wimbledon (February 2026) is typical of a job that is set up, installed and cleared the same day. What adds time: clearing a loft full of belongings, removing old degraded material, fitting raised loft boarding over the new depth, and ventilation or pipework detailing. Rafter and room-in-roof work is a different animal — days rather than hours, because every board is cut to fit between timbers.
Suspended floor: a few days
A suspended timber floor takes a few days for a typical ground floor. Access decides everything: working from a cellar or crawl space means no floor comes up and the job moves fast — our Camberwell suspended-floor job (February 2024) ran that way — while lifting and refitting boards room by room is slower and needs rooms emptied in turn. See our floor insulation service for the two approaches.
Internal wall insulation: a week per few rooms
IWI is sequenced room by room around a lived-in house, and on our jobs it runs at roughly a week per batch of rooms: each room takes around two to four working days through strip-out, boarding, and skim, with rooms overlapping as trades leapfrog. A single-room job like our East Dulwich install (13m² of wall, June 2026) is days; a multi-room project like Watford (May 2025) is a couple of weeks of phased work rather than one long siege.
The tail of an IWI job is finishing, not insulating — skim drying, skirtings, sockets, reveals and decoration-ready surfaces. Plaster drying adds calendar days when no one is on site, which is why "days of disruption" and "days until you can paint" are different numbers. The full lived-in-house playbook — sequencing, dust control, which rooms first — is in insulating while you live there.
External wall insulation: several weeks, scaffold to scaffold
A whole-house EWI wrap is a several-week project from scaffold up to scaffold down. The stages, in order: scaffold erection; preparation and beading; boarding and mechanical fixing; basecoat with reinforcing mesh; finish render; detailing (reveals, sills, pipework, eaves); making good; and the scaffold strike. Our recent completed wraps — 58m² at Worcester Park, 102m² at Ruislip — both followed that arc, and the difference in their durations was driven less by area than by detail count and season.
Two things make EWI the least predictable measure. First, weather: the render stages are wet trades that cannot go on in frost or rain and behave badly on hot sun-baked walls, so wet-trade days move with the forecast — the full picture is in when to book EWI. Second, detailing: window reveals, sills, downpipes, soffits and junctions are slow, skilled work, and a house with bays and dormers simply has more of them than a plain box. Both are worth the time — the detailing is where EWI succeeds or fails.
Survey to quote to start: the real pipeline
- Enquiry to survey: typically within days — surveys run all year, whatever the season.
- Survey to quote: 24 hours. That is our standard — a fixed, itemised quote the day after we have measured, not a fortnight of chasing.
- Quote to start: varies by season. This is the honest variable. Internal measures — IWI, loft, floor — can usually start soon in any month. EWI queues seasonally: spring slots fill first every year with people who enquired in winter, autumn is the underrated shorter queue, and winter EWI runs with a weather-managed programme.
The practical takeaway: the paperwork is never the bottleneck — the install slot is. If you want EWI in the warm months, get surveyed in the cold ones.
Combining measures changes the arithmetic in your favour. If you are doing EWI and a loft top-up, the loft day disappears inside the EWI programme; a floor job can run while the render is curing outside. One mobilisation, one set of protection, one clean-up — which is why a combined project is nearly always shorter (and cheaper per measure) than the same measures booked a year apart. It is worth pricing both ways before you decide; the real prices from our quote book show how project size moves the per-m² cost.
Honest caveat: what extends a job
Any duration you are quoted — ours included — flexes with what the job uncovers and what the sky does. The usual suspects:
- Weather on EWI — render waits for its window; a wet fortnight adds a wet fortnight.
- Detailing density — bays, dormers, complex eaves and lots of penetrations all add days of skilled work per elevation.
- What preparation uncovers — blown render, damp masonry or rotten timber has to be put right before insulation goes over it; covering it up faster is not a service.
- Access surprises — shared drives, conservatories under scaffold lines, parking restrictions.
A programme quoted honestly, with those risks named up front, beats a short one that quietly doubles. Ours come with the fixed price attached. Get a free, fixed, itemised quote — the quote arrives within 24 hours of survey, and it will tell you the programme for your house, not an average one.
Duration FAQs
How long does loft insulation take?
A straightforward cold-loft top-up is usually a day — often a morning once the crew is on site. Add time if old material has to come out, if the loft is full of stored belongings, or if raised boarding for storage is going in over the new depth.
How long does external wall insulation take?
A whole-house EWI project runs several weeks including scaffold — erecting access, boarding and fixing, basecoat and mesh, finish render, detailing and making good, then the scaffold strike. Weather sets the pace of the wet render stages, so winter programmes carry more float than summer ones.
How long does internal wall insulation take per room?
On our jobs IWI runs at roughly a week per few rooms: each room takes about two to four working days through strip-out, boarding and skim, and rooms are done in sequence so you keep the rest of the house. Plaster drying adds calendar time before you can decorate, but not crew time.
How quickly can I get a quote and a start date?
Our standard is a fixed, itemised quote within 24 hours of the survey. The wait for a start date is seasonal: spring EWI slots are claimed by people who enquired in winter, while internal measures can usually start sooner. Enquiring early costs nothing — the quote is free and stays valid while you decide.
Why did my neighbour’s EWI overrun?
Almost always weather or detailing. Render cannot be applied into frost or rain and dries badly on hot sun-struck walls, so wet-trade days slip; and the fiddly work — reveals, sills, pipework, eaves — is where honest jobs spend their time. An installer who quotes a suspiciously short EWI programme is usually planning to skip the detailing, not to work faster.