Frequently Asked Questions

Usually not. Rooflights on a house generally fall under permitted development, which allows a roof alteration projecting no more than 150mm above the existing roof plane, sitting below the highest part of the roof. A standard roof window set into a tiled pitch sits comfortably inside that. A roof lantern on a kerb does not, which is covered below. The exceptions that catch people out are conservation areas, listed buildings, Article 4 areas and flats, where permitted development rights are reduced or absent. We tell you which category your property is in at survey, before anything is ordered.

Permitted development for roof alterations to a dwelling house generally allows an addition that projects no more than 150mm above the plane of the existing roof slope, and that does not exceed the height of the highest part of the roof. Flat rooflights typically add 100mm to 150mm and clear it. A roof lantern on a 150mm kerb with a 300mm glazed pitch is around 450mm above the roof plane and does not. In practice, where a lantern is going on a new rear extension, the whole extension is assessed as one and the lantern goes with it. Where you are retrofitting a lantern onto an existing flat roof, the rule bites directly and a lawful development certificate is worth having.

Often yes, to the rear. Suffolk and north Essex carry an unusually high conservation density, Lavenham, Aldeburgh, Southwold, Dedham, Coggeshall, Framlingham, Debenham, Clare and much of central Ipswich among them. The general pattern is that a rooflight not visible from a public highway is frequently acceptable, while anything visible from the street usually needs a conservation-style unit with a slim or recessed profile, a flush external finish and often a black or dark finish rather than white plastic. Article 4 directions in some areas remove permitted development entirely. Speak to the conservation officer at your council early, because an informal conversation costs nothing and a refused application costs months.

Listed building consent is required for any rooflight, regardless of where it sits, including on a modern rear extension attached to the listed structure. There is no permitted development route on a listed building. Conservation-style rooflights with cast metal frames and a central glazing bar are the usual approved answer, and timber lanterns are far more likely to be accepted than slim anthracite aluminium. Lead times are longer and the units cost considerably more. We will not order anything for a listed property until consent is in hand, and we will tell you plainly if we think an application is unlikely to succeed.

Yes, in almost every case. Replacing or installing a rooflight is a controlled thermal element and, where an opening is being cut, structural work as well. Part L covers the U-value, Part B covers fire escape where a rooflight serves a loft conversion, and Part K covers guarding where glazing sits at low level. In a new extension it is covered by that project’s own Building Control application. A retrofit into an existing roof is notifiable in its own right.

For replacement rooflights in existing dwellings in England, the current standard is a whole-unit U-value of 2.2 W/m²K or better, assessed in the vertical plane, which is the convention rooflights are held to. That is a legal floor rather than a target. A thermally broken aluminium unit with argon-filled double glazing and a warm-edge spacer typically achieves 1.2 to 1.4. Triple glazing reaches roughly 0.9 to 1.1 at the cost of significant extra weight. New-build work is set by the SAP calculation for the whole dwelling rather than by a single element figure. We put the actual number on your quote so you can compare quotes properly.

We do. Where your work is notifiable, we handle the Building Control notification for you as a building notice or full plans application to your local authority. Practically, this is a form and a fee, usually a few hundred pounds, and an inspection by an independent Building Control officer who signs the work off in their own name. We tell you at survey which route your job needs and we work to the inspector’s requirements, and you have a compliant completion certificate in your file at the end, which is the document a conveyancing solicitor asks for when you sell.

A like-for-like roof window replacement is a single day, often half of one. Two or three units on the same visit is one to two days. A new opening in a pitched roof, including trimming rafters and forming and plastering the reveal, is one to two days. A roof lantern on a sound existing kerb is two days: scaffold and strip Monday morning, watertight by Monday afternoon, glazed and finished Tuesday. A new lantern opening with structural work is three to four days on site, plus whatever the engineer and Building Control need beforehand.

No. This is the fear nobody in this market answers properly, so here is the answer. On a replacement the roof is open for hours, not days. On a new opening it is usually open for most of the first day. In every case the target for day one is the same: covering dressed up and over the upstand, laps terminated, watertight with or without the unit on it. If weather makes finishing impossible we sheet and secure properly and come back, rather than pressing on and hoping. Nothing is ordered until it is measured and nothing is opened until the unit is physically in stock, so the roof is never open waiting on a delivery.

Access to the roof area and somewhere to put a scaffold or tower, parking within a reasonable carry of the property, an indoor space cleared under the opening, and consent or Building Control paperwork where the job needs it. If the room below is finished, sheets go down and furniture gets moved before anything is cut. We do not need you at home all day, but somebody should be there at the start and at handover.

Almost never through the glass. Modern sealed units and gaskets are good. Failures happen at the perimeter: an upstand too short for the exposure, an upstand measured 150mm at the high side of a falling roof and finishing at 90mm at the low side where water actually collects, a roof falling towards the upstand instead of away from it, a flashing kit that does not match the covering profile, or a detail whose watertightness depends on a bead of sealant. Sealant is a gasket, not a waterproofing layer. Any junction relying on it will fail in about five years.

Possibly not. Interstitial condensation gets reported as a leak constantly, and the giveaway is that it appears on cold clear nights and in January rather than during heavy rain. It comes from a cold-bridged upstand, an aluminium frame with no thermal break, or simply high humidity in a room with nowhere for moisture to go. Kitchens with a recirculating extractor rather than one venting outside are the classic case. We insulate upstands continuously with the roof insulation and we do not fit frames without a thermal break, which removes two of the three causes. The third one is a ventilation problem and no glazing specification will fix it.

It will if it is specified with clear glass. A rooflight faces the sky and takes more solar gain per square metre than any window in the house. The fix is at order stage: a solar control coating with a g-value between 0.28 and 0.38, which cuts solar heat to roughly a third while keeping light transmission above 60 per cent so the room still reads bright rather than tinted. On larger units an opening vent gives hot air at ceiling level somewhere to go. Both are cheap now and expensive later. If a quote you have received does not mention a g-value on a south-facing unit, the specification has not been thought about.

Chloride. Salt-laden air deposits on every exposed surface and the wetting and drying cycle concentrates it at fixing heads rather than washing it away, while wind-driven rain arrives horizontally at the vertical face of an upstand instead of falling on the glass. Grade 304 stainless fixings within a mile of open sea at Felixstowe, Harwich, Clacton or Aldeburgh commonly show rust staining down the frame within two or three winters. We use 316L stainless throughout on open-coast work, because the molybdenum content resists chloride pitting, along with marine-specification powder coating, upstands at 200mm rather than 150mm, mechanically fixed flashing terminations and isolation between dissimilar metals. Costs for that uplift are published on our costs page.

Usually not. Woodbridge, Melton, Manningtree, Wivenhoe, Shotley and Pin Mill sit on tidal saline water with real wind exposure across open water, but they do not carry open-sea salt loading. Upgraded fixings make sense, especially where a property directly overlooks the water. Full marine coating generally does not. We are not going to price the Deben as though it were Southwold. The bands are set out on our areas we cover page and confirmed at survey looking at your actual aspect.

Because a rooflight is a hole cut in your roof that has to stay watertight for years, and the detailing that decides whether it does is invisible once the scaffold comes down. We fit rooflights every week, on every kind of roof this region throws up, so the upstand, the flashing and the coastal specification are the things we do most rather than occasionally. You also get a fixed price after survey, a 10-year workmanship guarantee, and the manufacturer’s own product warranty on the unit alongside it.

Because a repair on a failed unit is a payment plan for a replacement you are going to buy anyway. A reseal costs a few hundred pounds and typically buys twelve to eighteen months. It does not address the blown sealed units, the perished gaskets, or the wet timber inside an upstand that has been taking water for three years, which is normally the real problem by the time anything shows on a ceiling. Do it three times over five years and you have spent a serious fraction of a replacement while the decay continues underneath. Meanwhile a unit from 2005 sits at a U-value around 2.8 to 3.2 against roughly 1.3 for what we would fit today, so the room stays cold as well. We replace, we rebuild the upstand where it needs rebuilding, and that is the intervention that actually ends the problem.

Our workmanship: the upstand, the weathering, the flashing, the fixings and the installation itself. Ten years, in writing, handed over at completion. The unit itself carries the manufacturer’s own warranty, typically ten years on a sealed unit and varying on motors and controls, and we hand that documentation over at the same time. The guarantee is transferable if you sell the house, which matters more than people expect given how many of these jobs are done ahead of a move.

We survey on the roof, not over the phone: structure, fall, covering, orientation, exposure band, access. You then get one written price, itemised, with the glazing specification and U-value on it. That figure does not move unless you change the specification. If the survey turns up something that changes the job, rotten decking, a covering at the end of its life, structure that will not carry what you want, you hear it at survey while you can still walk away for nothing. Published ranges for every service are on our costs page so you can sanity check the number before we ever visit.

A deposit covers the unit, because it is made to your surveyed size and cannot be resold to anyone else. The balance is due on completion, after the hose test and handover. No staged payments on domestic work of this size, and no cash. Bank transfer, invoiced.