Reading a replacement quotation properly

What should be itemised

1. The unit. Manufacturer, model, size code and glazing specification. Not “supply and fit rooflight”.

2. The flashing kit, and which profile. This is where cheap quotations economise, and a flat kit on a profiled tile leaks.

3. The insulation collar. A separate order line, frequently omitted, and its absence shows as reveal condensation months later.

4. Access. Scaffold or tower, and who provides it. A quotation silent on access for a first floor window is incomplete.

5. Making good. To what standard, and whether decoration is included. Usually it is not, and it should say so.

6. Disposal of the old unit.

7. Building Control, where the work is notifiable, and who notifies.

8. The contingency for decayed timber, with an indication of cost. Its absence does not mean the risk is absent.

Questions worth asking

Is the U-value whole unit or centre pane. Is the flashing kit correct for my covering. Is an insulation collar included. What happens if the timber is soft. Who notifies Building Control.

Guarantees

Two separate things: the manufacturer’s warranty on the product, and the installer’s guarantee on the workmanship. Most problems are installation problems, so the second is the one that matters. Ask how long, and what it covers.

Why the cheapest is cheapest

Usually one of: no scaffold where scaffold is needed, no insulation collar, a generic flashing kit, or no allowance for making good. None of those is visible on the day and all of them surface later.

Why two quotations for the same job differ by a factor of two

It is almost never the window. Unit prices are broadly comparable between suppliers, and a roof window from any mainstream manufacturer costs roughly what it costs.

The difference is in everything around it, and specifically in what has not been written down. A quotation that says roof window supplied and fitted with one number against it is not comparable with anything, and the gap between it and a detailed quotation is a measure of what has been left out rather than of margin.

Eight things should be named. Here is what each one is, and what its absence usually means.

1. The unit

Manufacturer, model, size code and glazing specification, with the whole unit U-value rather than the centre pane figure.

Without the size code you cannot tell whether you are being quoted a stock size or a made to measure one, and those differ in price and in lead time. Without the glazing specification you cannot tell whether solar control, acoustic laminate or obscure glazing is included, and none of those can sensibly be added later.

Without knowing whether the U-value is centre pane or whole unit, you cannot compare two quotations at all. Whole unit is always worse, frequently by 0.4 or more, and it is what the regulations use.

2. The flashing kit

Which profile, by name and part number, for your covering.

Kits are matched to the covering and they are not interchangeable: flat for slate, deep for profiled interlocking tiles, specific patterns for pantiles. A flat kit on a profiled tile leaves open voids under the tile channels where it crosses them, water gets under within a season, and because it enters below the flashing it appears inside as a leak that seems to come from nowhere.

This is the most common installation fault we find on other people’s work, and it is exactly where a cheap quotation economises, because the kit is a separate order line and nobody can see which one was used once the job is finished.

A quotation that cannot answer this question by name has not been written from a survey.

3. The insulation collar

The component that closes the gap between the frame and the structure on a pitched roof. On a flat roof, the equivalent is the kerb detail, and specifically whether the outer face of the kerb is insulated.

Both are separate order lines. Both are frequently omitted from a cheap price. And the symptom of their absence does not appear until the first cold spell months after the work, as condensation on the plaster reveal, at which point nobody connects the two.

On a flat roof this matters more than most people realise. A 1200 by 1800 rooflight has six metres of perimeter, and an uninsulated timber kerb punches straight through the roof insulation around all of it, presenting close to a square metre of poorly performing envelope. Insulating it is a sheet of rigid board and an hour.

Asking directly whether the kerb is insulated is the fastest way to tell who has detailed the job and who is fitting a unit.

4. Access

Tower or scaffold, who provides it, how long it stands, and whether a highway licence is needed and included.

This is the item that most often surprises people and it is the largest single variable between two quotations for the same window. A single storey rear slope reachable from a tower costs very little. A second storey needs scaffold. A terraced frontage over a pavement needs scaffold and a licence from the county council, which carries a fee, a wait and conditions.

A quotation that does not mention access on a two storey job has either not thought about it or is planning to add it later.

5. Making good

To what standard, and whether decoration is included.

Cheap quotations frequently stop at the plasterboard, which leaves you a taping and skimming job to arrange yourself, and that is a trade visit you did not budget for.

Ours is to a plastered finish ready for decoration as standard, and decoration is not included unless asked for. Whichever the arrangement, it should be stated rather than assumed.

Worth asking at the same time whether the reveal will be splayed or boxed square. A splayed reveal, cut back at an angle at head and sill, opens the beam of light out and can make a modest window feel considerably larger. It costs a little more in plastering and it is the best value decision available on any installation.

6. Disposal

Of the old unit, the old flashings and any broken tiles. A sealed glazing unit is heavy and sharp and it is not something you can put in a household bin or leave for the council.

On a like for like replacement that is a surprising volume of material. Where a quotation is silent, ask whether it is going with them or staying with you.

7. Building Control

Whether the work is notifiable, by which route, and whether it is included.

A rooflight is a controlled fitting, so even a straight replacement generally engages Part L. Forming or altering an opening engages Part A for structure. In a habitable loft room, Part B for means of escape.

The two routes are a competent person scheme, where the installer self certifies and notifies afterwards and you receive a certificate, or a building notice to the local authority with inspections and a completion certificate.

A quotation silent on this has left it to you, and that is the sort of thing discovered at the point of sale rather than the point of fitting. A conveyancing solicitor will ask, and the absence of a certificate produces a delay, an indemnity policy or a retention at exactly the wrong moment.

8. A stated contingency

For decayed timber, with an indication of cost.

Nothing about a replacement is certain until the old unit is out and the covering is back around the opening. On a unit that has been misting or leaking for years, decayed timber is a realistic possibility rather than a remote one.

A fixed price that assumes everything is sound is either carrying a hidden margin to cover the risk, in which case you pay for it whether or not anything is wrong, or it is going to change on the day.

An honest quotation names the possibility and prices it, so nothing is presented as a surprise afterwards.

The two guarantees

Separate cover from separate parties, and both should be stated.

The manufacturer warrants the product: typically the sealed unit against seal failure for a stated period, and the frame and mechanism for a shorter one. Read what it excludes, because most manufacturers exclude anything installed outside their own instructions, which means a badly fitted window can void the product warranty as well as leaking.

The installer guarantees the workmanship: the flashing, the underlay collar, the frame fixing, the insulation collar and the making good.

Most rooflight problems are installation problems rather than product failures, which is why the second is the one to ask about, and it is the one most often missing from a cheap quotation.

Worth asking too who handles a manufacturer’s warranty claim. On our work we do it, because you should not have to argue with a manufacturer about a product we chose and fitted.

Where cheap quotations actually save money

Four places, none of them visible when the job is finished.

A universal flashing kit rather than the correct profile for the covering. No insulation collar, or an uninsulated kerb. Making good that stops at the plasterboard. And, on a replacement where the old size is obsolete, forcing a modern unit into the existing opening and packing the difference rather than adapting the opening properly.

That last one survives about a year. The packing settles, the frame goes out of square, the sash stops closing evenly against the gasket, and water gets past. By then the covering is back on and nobody can see what was done.

What to do with the answers

Ask for the breakdown before comparing rather than after. Where one quotation is a long way below the others, the eight questions above will normally locate the difference, and it is usually two or three of them at once.

Where ours is higher than another and the itemisation does not explain it, ask us. We would rather lose a job on an honest number than win it on one that grows.

Comparing three quotations that are not comparable

The common situation is three figures with different scopes hidden inside them, and no way to see which is which.

The fix is to ask all three for the same breakdown rather than trying to reverse engineer it. Unit specification with the whole unit U value at your size, flashing kit with the profile named, insulation collar, access, making good, disposal, and VAT.

Once those are separated, the comparison becomes real and the cheap one usually stops being cheap.

The provisional sums

Timber condition around an old opening cannot be established until the unit is out. A good quotation carries a stated allowance at a stated rate, so that finding rot is a priced variation rather than a stoppage and an argument on the day.

The same applies to breakages in the covering on a roof of age, and to the kerb condition on a flat roof replacement.

A quotation that mentions none of these is not cheaper. It is less complete.

What to ask beyond the numbers

Which route the building control notification takes, and confirmation that the certificate comes to you.

Whether photographs of the collar and the vapour control layer will be provided before they are covered.

And what the programme is, including access up and down and the plaster drying period, so you know when the room will actually be finished rather than when the fitters leave.