Almost no commercial building can close for a rooflight replacement, so the method statement is as much of the specification as the sheet. The work is done a bay at a time, only as much roof is opened as can be closed weather-tight the same day, safety netting goes in beneath the work before any sheet comes off, the floor below is cleared and cordoned in advance, and out-of-hours working is used where the internal use cannot accommodate the work in normal hours. Done this way, a distribution centre or a factory keeps running while its roof is replaced over it.
This page sets out how that is done. It sits under our commercial skylight installation service, and it is for facilities managers and building owners who need the daylight, the safety or the weather-tightness fixed without shutting the operation down. For a first-person account of what staff on the floor actually notice, read across to commercial rooflight replacement in an occupied building.
Bay-by-bay phasing
The unit of work on an occupied building is the bay. A bay is opened, its rooflights replaced, and it is closed and handed back before the next is started. Working this way keeps the disruption to a small, defined footprint at any one time, rather than opening a whole roof and leaving the building exposed and half-usable for weeks.
Phasing is planned with your operations team around what happens below. Which bay is worked first depends on where the risk and the leaks are, but also on what can be cleared from underneath and when. Racking that can be emptied, plant that can be shut down for a shift, and vehicle routes that can be diverted all feed into the sequence. We would rather agree that on a plan a fortnight ahead than discover a fixed rack of live stock under the first bay on the morning we mean to open it.
Weather-tight by nightfall, every day
This is the commitment that matters most over a working building, and it governs how much roof is opened at once. Only as much is opened as can be closed and made weather-tight the same day. If the forecast turns, the day’s opening is reduced rather than gambled on. No roof of ours is left open overnight over an operating building, and there is no situation in which stock or plant gets rained on because a bay was being pushed to finish.
Open only what can be closed. This one rule drives the daily plan. It sets how many sheets come off in a session, how the weather forecast is read each morning, and why a wet week slows a programme rather than risking the building. A facilities manager can hold us to it: at the end of every working day the roof is closed and the building below is dry.
Netting and internal protection
Fall protection on an occupied building has to protect the operatives and the floor below at the same time.
- Safety netting is installed beneath the work area before any sheet is removed. It gives collective fall arrest for the operatives, and it catches tools, debris and old sheet material above a floor that may still be in use nearby.
- The existing rooflights are treated as fragile. The sheets being removed are, by their age, fragile surfaces. Nobody walks on or near them. Access across the roof is on staging, crawl boards or a platform that spans the openings.
- Where netting is not possible, in food production, clean areas or where the internal environment rules it out, the alternative is a fully covered working platform or a move to out-of-hours working when the floor below is empty.
- Internal protection below the work, sheeting over racking or plant that cannot be moved, keeps dust and debris off it while a bay is open.
Exclusion zones below
The floor directly beneath an open bay is not accessible while the roof above it is open, and the exclusion zone is set, cordoned and signed before work starts. This is agreed with your team so the zone is cleared of people, stock and traffic, and so alternative routes and storage are arranged in advance. The zone moves with the work, bay by bay, so only a small part of the building is out of use at any time. A clearly marked, well-communicated exclusion zone is what lets the rest of the building carry on normally right up to the cordon line.
Out-of-hours and shutdown working
Some buildings cannot be worked on during operating hours at all, and for those the work moves outside them.
| Building type | Common pattern | Why |
|---|---|---|
| Distribution and logistics | Nights or quiet shifts | Floors run late, exclusion zones easier when picking stops |
| Manufacturing | Planned shutdown or quiet week | Aligns with maintenance windows, plant can be isolated |
| Retail | Nights, before and after trading | No customers below, floor clear |
| Food production and clean areas | Out-of-hours, full internal protection | Netting often ruled out, hygiene controls apply |
Out-of-hours working attracts a premium for labour and for task lighting, and it is priced openly rather than absorbed and then argued about. Around the port and the A14 corridor, distribution sites frequently run late into the evening, so night working is often the only clear window, and it is planned for from the start rather than treated as an exception. Our how long a commercial rooflight programme takes answer covers how working windows affect duration.
Communication with site staff
Most of what goes wrong on an occupied building is a communication failure, not a technical one. A bay opened over stock nobody moved, a route blocked that a forklift needed, an alarm zone isolated without the duty manager knowing. The work runs on a shared plan.
- A pre-start walk with the operations team, agreeing the sequence, the exclusion zones, the access route and the working hours before anything is ordered.
- A named point of contact on both sides for the duration, so a change on either side is handled quickly.
- Daily coordination on which bay is open, which zone is closed, and what the weather is doing to the plan.
- Advance notice of anything that affects the building’s systems, the fire alarm, roof-mounted plant, or a smoke ventilation system that cannot simply be taken out of service.
A worked sequence for a single bay
It helps to see how one bay runs, because the whole programme is this repeated.
- The day before. The operations team clears and cordons the floor beneath the bay, moves stock, and diverts any routes that pass under it. The forecast is checked.
- First thing. Netting is confirmed in beneath the bay, edge protection and running lines are set, and the roof access route is opened. Nobody steps on the existing rooflights.
- Through the day. Only as many sheets are removed as can be replaced and closed before the end of the day. Old sheets come off, the purlins and fixing points are checked, the liner rooflight is fitted where the roof is twin skin, and the new sheet is set with its correct laps, sealant and fixings.
- Before nightfall. The bay is closed and made weather-tight. If the forecast turned, fewer sheets were opened, so the roof is always closed before nightfall.
- Next morning. The bay is checked, the cordon below is lifted once the floor is confirmed safe, and the team moves to the next bay.
Repeated across the roof, this is what a phased occupied-building programme is. Each bay is a self-contained unit of open, replace and close, so the building is never exposed and never more than one bay out of use at a time. Our programme timescale answer covers how many bays a day this runs at.
CDM and the paperwork behind it
Under the Construction (Design and Management) Regulations 2015, work on an occupied commercial building brings duties for the client as well as the contractor. The construction phase plan, the risk assessments and method statements for each phase including the fragile roof risk, the roof access and rescue plans, and the permit-to-work arrangements are all agreed with your team before mobilisation. Where the project size brings notification and principal-designer thresholds into play, that is flagged before work starts rather than after an inspector asks. We are the specialist contractor for the rooflight work, and we set out clearly where the client’s own duties sit.
Can you replace our rooflights without closing the building?
Yes, and most of our commercial work is done that way. We phase bay by bay, clear and cordon the floor beneath each bay in advance with your team, net beneath the work before any sheet comes off, and close every bay weather-tight before the end of the working day. Where the internal use rules out working in normal hours, food production and clean areas being common cases, we move to out-of-hours or shutdown working.
What happens to the area under the bay being worked on?
It becomes an exclusion zone, cordoned and signed, cleared of people, stock and traffic before the roof above is opened. The zone moves with the work, one bay at a time, so only a small part of the building is out of use at any point and the rest carries on normally up to the cordon. Alternative routes and storage are arranged in advance with your operations team.
Will you leave the roof open overnight?
No. We open only as much roof as we can close and make weather-tight the same day, and if the forecast turns we reduce the day’s opening rather than gamble on it. No roof of ours is left open overnight over an operating building. This is the rule that most protects the stock and plant below, and you can hold us to it.
Keep operating while your roof is replaced
A working building does not have to stop for its rooflights to be replaced. We plan the phasing around your operation, net and cordon before we open anything, close every bay the same day, and work out of hours where that is what your building needs. The programme we give you is built from your site and your operating pattern.
Request a survey and a phasing plan. Read across to how a phased programme is planned and what commercial rooflight replacement costs, and see the costs page.
Thinking about this job? We survey across Ipswich, Suffolk and north Essex and give you a fixed price before any work starts, with a 10-year workmanship guarantee.