How Do You Plan a Phased Rooflight Replacement Programme?
You plan a phased rooflight replacement programme by surveying and grading the whole roof first, prioritising by risk and leak history rather than geography, grouping the work into bays that can each be finished and closed, and spreading those phases across financial years so each sits inside a year’s capital budget. The roof plan and fragility record are updated after every phase.
That is the shape of it. This answer, which sits under our commercial skylight installation service, sets out each step for facilities managers and building owners who have a large roof and a budget that will not stretch to all of it at once.
Step one: survey and grade the whole roof
The programme is built on a full condition survey. Every rooflight position goes on a plan with its material, estimated age, degradation grade, light transmission loss, evidence of water ingress, and a fragility position. Without this you are guessing, and guessing usually means reacting to whichever sheet leaks next. The grading also shows the pattern across the roof, and there always is one: south-facing slopes age faster than north, exposed areas faster than sheltered. Our GRP rooflight degradation page covers how the grading is done.
Step two: prioritise by risk, not geography
Phase one is not the nearest corner. It is whatever carries the highest risk. That means:
- Any fragile rooflight over a walking route, a roof access point, or plant that needs regular maintenance, because that is where someone could fall through.
- Any position with active water ingress over stock, racking or electrical equipment.
- The worst-graded sheets, which are both the fall risk and the leak source.
Prioritising by risk means the programme clears the things that could hurt someone or ruin stock first, and leaves the sound, sheltered sheets to the end. A programme ordered by geography clears a tidy corner and leaves a fragile sheet over a fire exit for year three.
Step three: group into closable bays
Work is grouped into bays or slopes that can each be completed and closed as a unit, so every phase leaves a coherent, documented, weather-tight result rather than a scatter of replacements across the roof. This also shares the access cost, which is most of the price, across every sheet in the bay.
Step four: budget across financial years
Each phase is priced separately so it can sit inside a specific year’s capital allocation, and the whole programme is priced together so you can see the total. A large roof is commonly spread over two to four financial years. There is a trade-off to set: more phases mean smaller annual bills but more mobilisations, and each mobilisation carries its own access and set-up cost.
How phasing affects the unit price. Every phase pays its own access and mobilisation cost, so splitting a roof into more phases raises the total. A roof done in one visit has the lowest unit rate, and a roof done in six annual phases the highest, for the same sheets. The sensible programme balances the cost of your capital being tied up against the cost of mobilising repeatedly. We show both figures so the decision is yours to make with the numbers in front of you.
Step five: keep the record live
The roof plan and the fragility record are updated after every phase. This is the point facilities managers value most: at any moment in a multi-year programme you can state precisely which parts of the roof are documented non-fragile and which are still outstanding. A partially completed programme with a current plan is a defensible position in front of an inspector or an insurer. The same roof with no record is a much worse conversation.
What this looks like around Ipswich
Much of the industrial stock across Ipswich, the port estates and the Suffolk and north Essex estates went up between the 1970s and early 2000s, so a great many roofs are now at or past the end of their original rooflight life all at once. That is exactly the situation a phased programme is for: too much to do in one capital year, too risky to leave. On the coastal belt, around Felixstowe and Harwich, chloride exposure pushes sheets to the shorter end of their life, so the risk-based prioritisation there tends to bring forward the exposed slopes. Inland, around Stowmarket, condition and daylight drive the order rather than corrosion.
How many phases should a rooflight programme have?
As few as your capital budget allows, because each phase carries its own access and mobilisation cost. Large roofs are commonly spread over two to four financial years. The right number balances the annual bill you can absorb against the extra cost of mobilising repeatedly, and it is set at the survey with both figures on the table.
Does phasing cost more than doing it all at once?
Yes, modestly, because every phase pays its own access and set-up. A roof done in one visit has the lowest unit rate. Phasing trades that against spreading the capital cost across years and clearing the highest risks first. For most large roofs the ability to fund it year by year outweighs the small premium, but we show both numbers so you can choose.
Get your programme planned
A phased programme starts with a full graded survey. We record every position, prioritise by risk, group the work into closable bays, and give you a costed phase plan you can fund across financial years, with the record updated after each phase.
Request a survey. Read across to how long a programme takes, when industrial rooflights should be replaced, and replacing rooflights during a roof refurbishment.
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.