No, and this is the single most common gap in a quotation. A roof window is supplied as a window. The flashing kit that weathers it into the covering is a separate product, chosen for the profile of your tiles or slates and for the size code of the window. Two quotations that look different in price often differ only in whether the kit is in them.
What a flashing kit does
Explained in full, with how it sheds water, on what is a flashing kit.
This page is about choosing and buying one rather than about how it works.
Why it is a separate product
Because the same window goes onto many different roofs.
A window is one thing, but the covering around it might be a deep pantile, a flat concrete tile, a natural slate or a metal sheet, and each needs a different form to seal against.
Selling the two together would mean a different window for every roof.
The main division
Profiled against flat, and it is the first question.
One family of kits suits profiled coverings up to a stated depth, with a skirt formed to sit down into the contour. Another suits slate and flat tiles, where the skirt sits against a plane.
Choosing the wrong family leaves a gap the sealant cannot close.
Measuring the profile depth
A tape across a tile, and it takes a minute.
Kits state a maximum profile depth they will accommodate, and a deep interlocking pantile sits close to the limit on some of them.
It is measured rather than judged by eye.
Recessed kits
A different kit for a different appearance.
A recessed kit sets the frame deeper so the glass sits closer to the covering line, which reads far flatter from the ground and matters on a visible slope.
What that involves is on what is a VELUX recessed installation.
Combination kits
For two or more windows set close together.
Rather than two single kits with an awkward strip of covering between them, a combination kit carries a formed gutter between the frames and weathers the pair as one.
The spacing is fixed by the kit, which is why it is decided before the roof is opened.
Side by side against stacked
Different kits again.
Windows across the slope need a vertical gutter between them. Windows up the slope need a bridging flashing between the head of one and the sill of the next.
Which arrangement suits a room is on how far apart should two roof windows be.
Kits for a very shallow pitch
Where the specification changes.
Below the ordinary pitch range some windows can still be used with an additional underfelt collar specified for the purpose, and the kit is ordered accordingly.
The pitch limits are on what is the minimum pitch for a roof window.
What comes in the box
Formed pressings and the fixings, not raw material.
Head, sill and side sections shaped for the size code, plus the clips and screws, so the work on the roof is fitting rather than fabricating.
What is not in it
The underlay collar, on most kits.
The membrane detail around the opening is a separate item and it is the part that decides whether water reaching the underlay finds its way out.
It is worth confirming that it is included in a quotation.
Reusing an old kit
Occasionally sound, usually not worth it. Where a kit is undisturbed, matched to the same frame size and in good condition, parts can stay. Where it has been patched, dressed over, or is a different generation, it is renewed.
A kit is a small line against the risk of a leak in a finished room.
Lead coverings and one off details
Where a kit alone is not the answer.
A window meeting a valley, a hip, a wall abutment or a lead covering needs work beyond the boxed components, and that is roofing rather than assembly.
Why a homemade flashing fails
Not immediately, which is the problem.
Improvised lead or sealant around a frame will hold water out for a season or two, then move, crack or lift, and the failure appears in a decorated room.
The sequence is always the same.
What to check on a quotation
Three lines. That a kit is included, which type it is, and whether the underlay collar and the insulation collar are in as well.
With those, two quotations become comparable.
What the roof survey establishes
The covering, the profile depth and the pitch.
Those three between them decide the kit entirely, and they are taken on the roof rather than described over the phone.
Ordering time
Worth knowing when a date is tight.
Kits for common coverings and common size codes are stocked. Recessed and combination kits for unusual sizes can carry a wait, and the install date follows the delivery.
What a kit costs against the window
A fraction, and it is the wrong place to save.
Against the unit, the access and the making good, a flashing kit is a small line, and it is the component that decides whether the whole installation keeps water out for thirty years.
Where it sits in a quotation is on how much does a VELUX window cost.
Where the covering has been changed since
A situation that comes up on a re roofed house.
A window fitted under a slate roof that has since been recovered in concrete tile has a kit made for the wrong profile, and it will have been made to work with sealant rather than by form.
It is worth looking at when any work is being done nearby.
What we list
We list the kit as its own line with the type named, and we replace a kit on a like for like job unless there is a clear reason the existing one should stay.
The rest is on the VELUX window installation page.
Thinking about this job? We survey across Worthing, West Sussex and the South Downs and give you a fixed price before any work starts, with a 10-year workmanship guarantee.