Guide · Skylight & Rooflight Installation & Replacement Chelmsford
What a replacement quotation should contain
A replacement rooflight is one of the easier jobs in building to quote badly, because the visible part is a single product and the price of that product is public. Everything that separates a good installation from a poor one is buried under the covering or hidden in the reveal, and none of it shows up in a figure written next to the words “supply and fit rooflight”.
This page sets out, line by line, what a written quotation for a rooflight replacement should actually say. It is written so that two quotations can be laid side by side and compared on what they include rather than on which number is smaller, which is usually the only useful comparison available.
The two figures, and what each one is worth
Sunspire quotes in two stages, and the distinction matters when reading anything from anybody.
The first is a range, given by email once the basics are known: what the unit is, roughly what size, what the roof covering is and how it is reached. A range is honest about being a range and it is enough to decide whether to go further. The second is a fixed written figure after a survey, and it is fixed because the survey has answered the questions that make it vary. A single firm number offered before anybody has been on the roof is not a price. It is a starting position, and the conversation that adjusts it happens on the day with the covering already off.
Identifying what is being taken out
A quotation should begin by naming the existing unit, and it is a line that is very often missing.
The manufacturer and model where a data plate exists, or a plain description where it does not: twin skin polycarbonate dome on aluminium kerb frame, centre pivot timber roof window in concrete interlocking tile. The measured size, and which dimension has been measured. Its position on the roof, where there is more than one. This does two things. It confirms the survey looked at the right unit, which matters on a bungalow with four of them, and it fixes what the price was based on if anything turns out differently.
Naming the new unit precisely
The line describing what is being fitted should be specific enough that the same unit could be ordered by somebody else from the quotation alone.
Manufacturer. Model or range name. Size code where the maker uses one, and the millimetre dimensions alongside it. Whether the unit is fixed or opening, and if opening, how it is operated. Frame material and finish, including the external colour reference where it is a coated aluminium frame. And the opening direction or hinge arrangement on a roof window. Any of those left vague is a decision that somebody else will make later, and it will be made on the basis of what is easy to get rather than what suits the room.
A unit described in enough detail to be re-ordered from the quotation is a unit that will arrive as intended.
The glazing line, and the numbers on it
The glass is where the largest performance differences hide, and it deserves its own line rather than the word “double glazed”.
Six figures make that line complete: the pane build-up, the whole unit U-value with the measurement basis stated next to it, the g-value, the light transmission, the cavity gas, and any coating on the exposed outer face. The measurement basis matters because a centre pane figure and a whole unit figure for the same product can differ substantially, and only one of them is what Part L is assessed against. Where solar control, acoustic asymmetry, obscuration or a self cleaning coating have been specified, each should be named. The reasoning behind those choices is set out on upgrading the glass while the roof is open.
What is happening to the upstand, one way or the other
On a flat roof replacement this is the line that moves the price most, and it should say which of two things has been priced.
Either the existing upstand is retained, in which case the quotation states that the survey found it sound, level and adequate in height, with the measured height given. Or it is rebuilt, in which case the quotation says what is being built: material, dimensions, insulation to the outside face, and the finished height above the covering. What should not appear is a form of words making the price conditional on what is found when the unit comes off. That is the survey’s job, and the reasoning behind the decision is covered on reusing an existing kerb.
Reinstating the roof surface, covering by covering
Every replacement involves taking the roof surface back around the opening and putting it back again, and how much comes back depends entirely on the material.
| Covering | What the line should say |
|---|---|
| Single ply membrane | Extent cut back, new section hot air welded in, joint tested |
| Felt, torch on or pour and roll | Number of layers stripped and rebuilt, and how far out |
| GRP | Area cut back, new matting and resin, and the weather it needs to cure |
| Tile or slate | Courses lifted and reset, and the allowance for breakages |
| Asphalt | Named as hot work with a specialist, and priced as such |
The two things to look for are the extent, expressed in courses or in millimetres out from the opening, and who is doing it. Where two trades are involved the boundary between them is the interesting part of the quotation, because that boundary is where things get left undone.
The flashing kit, named by covering profile
On a pitched roof the flashing kit is always new, and it should be named rather than assumed.
Kits are matched to a specific frame profile and a specific covering depth. A plain clay tile, a deep concrete interlocking tile, a natural slate and a low profile pantile each take a different one, and the depth of the covering is what decides it. The quotation should say which kit, and whether it is a standard or a recessed installation, because that changes how the unit sits relative to the tile surface and therefore how it looks from the garden. Where the existing detail was hand dressed lead, the quotation should say that the lead is stripped and goes for recycling rather than into a skip.
The underlay apron, which almost nobody lists
Under the tiles is a felt or membrane whose job around a rooflight is to collect anything that gets past the covering and take it around the frame and back onto the roof below.
On any roof window older than about twenty years that material is brittle at the opening and torn at the fixings, and it has to be cut back to sound material with a new drainage apron dressed over the head of the frame and lapped into the existing underlay above. It costs very little and it prevents the specific failure that looks like a leaking window and is not one. A quotation that names this line has had somebody thinking about water rather than about products.
The reveal, and where the finish stops
The internal lining is the part of a replacement most likely to be left ambiguous, and it is the part the client looks at every day.
The quotation should say what condition the reveal is left in and who takes it from there. Plastered and left ready to decorate is the usual and reasonable position, because matching an existing paint colour on a sloping ceiling belongs with whoever chose it. What matters is that it says so. It should also say whether the reveal is being reinstated as it was or splayed, since splaying an existing square reveal while the plaster is off costs a little and roughly doubles the apparent size of the opening, and it is the cheapest improvement on the whole job.
Insulation and the vapour layer at the perimeter
Two lines that are invisible forever once the plasterboard goes back, and that decide whether the reveal stays clean.
The first is an insulated collar around the frame, connecting the frame to whatever insulation the roof or the slope carries, so that the perimeter of the opening is not a cold ring. The second is the air and vapour control layer, cut when the lining came off, taped back to the new frame so that warm moist room air is not moving into the build-up at its coldest point. Neither is expensive and neither can be added later. A quotation that names them is describing the four invisible details that the ten-year workmanship guarantee actually covers.
Openers, wiring and anything with a motor
Where the new unit opens, how it opens belongs in writing, because retrofitting the answer is disproportionately disruptive.
Manual with a pole, and whether the pole is included and how long it is. Electric mains powered, and who is running the supply, from where, and whether an electrician is included and certificated. Low voltage from a transformer, and where the transformer sits. Or solar powered, carrying its own panel and battery on the frame with no cable at all, which on a finished ceiling under a flat roof is very often the deciding factor. Rain sensors, remote controls and any wall switch position should be named. The electric rooflight page goes into how each option is installed.
Blinds, and whether they are on the order
Blinds run in side channels within the frame and those channels belong to the frame generation they were made for, so an existing blind will not transfer onto a new unit.
The quotation should therefore say one of three things: blinds supplied and fitted with the unit, with the type and colour named. Or the unit ordered with the channel provision so a blind can be added later. Or neither. All three are legitimate positions and only the first two are recoverable afterwards without difficulty. In a loft bedroom under an east facing slope, this line is doing more work than it looks like it is.
Notification, and the certificate that arrives later
Replacing a rooflight in an existing dwelling is controlled work under Building Regulations in England, so somebody has to notify it.
Sunspire handles the notification as part of the job and the completion paperwork follows in the client’s name. The quotation should say explicitly that this is included, because the value of that paperwork is not felt on the day. It is felt at sale, when a buyer’s solicitor asks for certificates covering any alteration and an undocumented rooflight turns into a retention on the completion money or an indemnity policy nobody wanted. Where a quotation is silent on notification, that is the single most useful question to ask about it.
Access, and how the roof is actually reached
Access is the line that most often accounts for a genuine difference between two otherwise identical quotations.
A rear extension roof reached from a garden with a ladder and a roof ladder is one thing. A third floor rear slope over a narrow side return needs scaffold, and scaffold has a hire period, an erection date and a dismantling date attached to it. A tower, an edge protection arrangement or a mechanical lift for a large unit each belong on the quotation with what they cost and how long they are on site. Where access crosses a neighbour’s land, that should be named as something to arrange rather than assumed.
Removals, skips and the street outside
An old rooflight generates more material than people expect, particularly a dome, and the removal of it is a real cost.
The quotation should say what is being taken away and by whom: the old unit, the old kerb frame, broken tiles, stripped felt, plaster from the reveal. It should say whether a skip is included, and where it is going to stand, since a skip on a road in a Chelmsford terrace needs a permit and a bay. Where the survey has identified suspect material in an older roof, the quotation should name it as sampled and, if confirmed, handled by a specialist licensed for that work, with the programme adjusted accordingly.
Programme, lead time and the weather
Dates on a rooflight quotation carry more information than dates on most trades, because the roof is open in the middle of the job.
Three figures are useful: the lead time on the unit from order, the number of working days on site, and the point at which the unit is checked against the measured opening. The last one is the important one, because nothing should be stripped until the new unit is on site, unwrapped and confirmed correct. Where a job runs into a second day, the quotation should state that the opening is decked and weathered overnight rather than sheeted. The roof is closed and watertight at the end of every working day, and that is a method statement rather than an aspiration.
Payment, guarantee and the words that hide a gap
The last section of a quotation is where the commercial terms sit, and it is worth reading as carefully as the technical lines.
Payment stages should be named against milestones rather than dates. The guarantee should appear as two separate things: the manufacturer’s warranty on the unit, with its term, and the workmanship guarantee on the installation, which at Sunspire runs to ten years. And the phrases to look at twice are the elastic ones. “Subject to condition of existing kerb”, “allowance for making good”, “if required” and “provisional sum” each mean a number that has not been established yet, and each of them is answerable by a survey. A quotation with none of those in it is a quotation somebody has actually done the work to write. The costs page explains how the ranges behind these figures are built, and the guides cover the decisions each line represents.
Keep reading
More on skylight & rooflight installation & replacement chelmsford
Sizing a rooflight for the room
Read the guide →Roof window or rooflight, and the difference
Read the guide →Flat roof against pitched roof rooflights
Read the guide →What happens on installation day
Read the guide →Cleaning and maintaining a rooflight
Read the guide →All about skylight & rooflight installation & replacement chelmsford →
Get a quote
Tell us about your roof
We start with the building, the covering and the slope. Then we tell you what will suit it, and what it will cost, as a fixed written number.
- Surveyed before it is priced
- 10-year workmanship guarantee
- Building Control notification handled
- New installations and replacements