Questions Answered
Two hundred of the questions we are actually asked, answered without the sales pitch.
200 pages across 10 subjects
These are the questions we are actually asked, on the phone and at surveys, answered in the same words we would use standing in your kitchen.
Where the answer is “it depends”, the page says what it depends on. Where the answer is “no”, it says no.
How this library works

Every question here came from somebody standing in a room, on a phone, or in a loft, asking us something real. We wrote the answers down because the same questions come round every week and because a straight answer is more use to you than a callback.
Each answer is a page rather than a paragraph. If the honest response is that it depends, the page says what it depends on and how to work out which case you are in, because that is genuinely more useful than a number that turns out not to apply to your roof.
What is in here
Cost questions. What things cost, why quotations differ so much for what looks like the same job, what is normally included and what is normally extra, and which variables actually move the number. We give ranges rather than single figures because a range you can trust beats a figure you cannot.
Permission questions. Whether you need planning permission, when permitted development covers you, what changes in a conservation area, and why listed buildings work differently from everything else. These are the questions where a wrong assumption is most expensive, and where the answer genuinely varies by address.
Product questions. Fixed against opening, manual against electric, double against triple, rigid against flexible, one large rooflight against several small ones. Trade offs rather than winners, with the situation each one suits.
Problem questions. Why a rooflight is misting, why there is water on the reveal, why a sash will not close, whether a noise is a fault, and which of those need somebody out and which do not. Condensation and leaks look identical to a homeowner and have completely different fixes, so a good part of this section is about telling them apart.
Process questions. How long jobs take, what happens on the day, what we need from you, what the weather does to a programme, and what the guarantee actually covers.
How to use it
The answers are grouped under the service they belong to, so if you know what you are having done, start from that service page and work through the questions attached to it. If you are earlier than that and still working out what you need, the guides are the better starting point: they cover a whole topic in depth where an answer covers one question.
Nothing here is a substitute for somebody looking at your roof. It is meant to get you to the point where the conversation with us is a short one, where you already know roughly what you want and roughly what it should cost, and where the survey confirms rather than reveals.
If your question is not here
Ask it. We add pages when a question comes up more than once, and the fastest way to get something added is to be the second person to ask. There is no charge for a question and no obligation attached to asking one.
For anything specific to your property, a survey is the honest answer, and we will say so rather than guessing from a description. Where a photograph is enough, we will tell you that too and save you the appointment.
Why the answers are longer than the questions
A one line answer to a rooflight question is usually a wrong answer with the conditions removed. What a replacement costs depends on whether the opening is reused, what the covering is and how the roof is reached. Whether you need permission depends on the listing, the designation and the elevation. Giving a single figure or a flat yes would be quicker to read and would mislead most of the people reading it.
So each answer states the conditions, tells you how to work out which one you are in, and gives a range rather than a number. The pages are a few minutes each and they are written to be read once and then acted on, not to be scrolled past on the way to a phone number.
Kept current
Building Regulations change, permitted development rules change, product ranges are discontinued and size codes go obsolete. Where something here is tied to a rule or a product, we revisit it when the rule or the product moves. Where an answer describes a judgement rather than a rule, it reflects how we actually work rather than an industry position.
Nothing here replaces a survey
These pages are written to get you to the point where the conversation with us is a short one: where you already know roughly what you want, roughly what it should cost, and what questions to ask whoever quotes.
What they cannot do is tell you what is under your covering, whether the timber around an existing opening is sound, or whether the rafter spacing at the position you want matches the rest of the slope. That is what a survey is for, and it is free.







The questions we are asked most
Roof Lantern Installation
20 answersQuestions
- What is a roof lantern?
- How much does a roof lantern cost?
- How big can a roof lantern be?
- Do roof lanterns need planning permission?
- Do roof lanterns leak?
- Can a roof lantern be opened?
- Do roof lanterns need a steel beam?
- How long does a roof lantern take to fit?
- Can a roof lantern have blinds?
- Are roof lanterns noisy in rain?
- Do roof lanterns lose a lot of heat?
- Do roof lanterns make a kitchen too hot?
- What pitch does a roof lantern need?
- Can you fit a roof lantern yourself?
- Can a roof lantern go on a flat roof with no fall?
- How do you clean a roof lantern?
- What colour should a roof lantern frame be?
- Do roof lanterns need a survey before ordering?
- Can a roof lantern be fitted to an existing extension?
- Are roof lanterns better than flat rooflights?
Flat Roof Rooflight Installation
20 answersQuestions
- Can a rooflight be fitted to a flat roof?
- How much does a flat roof rooflight cost?
- Do flat rooflights need to be sloped?
- Can you stand on a flat rooflight to clean it?
- Do flat rooflights hold water after rain?
- Are flat rooflights secure?
- Do flat rooflights need building regulations?
- Can a flat rooflight be opened?
- What is the maximum size of a flat rooflight?
- Do flat rooflights cause condensation?
- Can a flat rooflight go over a shower?
- What is the minimum fall for a flat roof with a rooflight?
- Can you fit a flat rooflight to a felt roof?
- Can a flat rooflight be fitted to a green roof?
- Snow and standing water on a flat rooflight
- Can two rooflights be joined together?
- Can you replace a rooflight on a flat roof?
- What is a rooflight upstand?
- How high should a rooflight kerb be?
- Can rooflights be fitted to a garage roof?
Roof Window Installation
20 answersQuestions
- What is a roof window?
- How much does a roof window cost to fit?
- What size roof window should I get?
- Can a roof window be an escape window?
- Can a roof window be fitted in a bathroom?
- How long does a roof window last?
- Do roof windows need servicing?
- Are roof windows noisy in rain?
- Do roof windows come in standard sizes?
- Can a roof window be painted?
- Do roof windows come with blinds?
- What is a roof window flashing kit?
- Can two roof windows share one flashing?
- How steep can a roof be for a roof window?
- Can you replace a roof window with a bigger one?
- Why is my roof window misted up inside the glass?
- How do you clean the outside of a roof window?
- What is the difference between centre pivot and top hung?
- Roof windows in a bedroom and blackout
- Can a rooflight be fitted between rafters?
VELUX Window Installation
20 answersQuestions
- Which roof window brand is best?
- How do I find out what rooflight I have?
- Can you match my existing rooflight?
- Can you replace just the glass in a rooflight?
- Matching a replacement to an obsolete size
- How long does a skylight replacement take?
- How much does it cost to replace a skylight?
- Is a misted rooflight an emergency?
- Can you replace a rooflight without scaffolding?
- Can you replace a rooflight from inside the room?
- Do replacement rooflights need building regulations?
- Should I replace all my rooflights at once?
- Is it cheaper to replace or repaint a rooflight frame?
- What is found when the old unit comes out?
- Replacing several rooflights at once
- Can a bigger rooflight go in the same opening?
- Do I need permission to replace a rooflight?
- Can a rooflight be replaced in winter?
- What a replacement quotation should contain
- Telling a failed unit from a failed installation
Electric and Opening Rooflights
20 answersQuestions
- Can rooflights be opened electrically?
- How much does an electric rooflight cost?
- Do electric rooflights need an electrician?
- Are electric rooflights noisy when opening?
- Do electric rooflights close automatically in rain?
- What happens to an electric rooflight in a power cut?
- Can an electric rooflight be opened manually?
- Do electric rooflights leak more?
- How long do electric rooflight motors last?
- Can you convert a manual rooflight to electric?
- Do electric rooflights need a socket in the roof?
- Are solar powered rooflights any good?
- Can you open a rooflight from your phone?
- What maintenance does an electric rooflight need?
- Do you need a rain sensor?
- Can electric blinds be added later?
- Are electric rooflights worth the extra cost?
- Can electric rooflights be fitted to old buildings?
- What is a chain actuator?
- How many electric rooflights can one switch control?
Energy Efficient Rooflights
20 answersQuestions
- What is the most energy efficient rooflight?
- What U-value should a rooflight have?
- Are rooflights bad for insulation?
- Do rooflights lose more heat than windows?
- Is triple glazing worth it in a rooflight?
- What is a g-value?
- What glass stops solar gain?
- Will a rooflight make my room too hot?
- How do you stop a rooflight overheating?
- Do solar control rooflights make a room dark?
- Does a rooflight affect an EPC rating?
- Do rooflights meet current building regulations?
- What is a warm edge spacer?
- How much light does a rooflight actually give?
- Do rooflights work on a north facing slope?
- Can you retrofit better glass into a rooflight?
- Do rooflights need trickle vents?
- Upgrading the glass while the roof is open
- Do rooflights add value to a house?
- Rooflights and Part L for a replacement
Replacing a Failed or Misted Rooflight
20 answersQuestions
- Why is my flat rooflight leaking?
- Do rooflights leak?
- How long does a rooflight last?
- Signs a rooflight needs replacing
- What happens to the plaster around the opening?
- What if the timber around the opening has gone soft?
- Does fitting a rooflight weaken the roof?
- How is a rooflight made watertight?
- What causes condensation on a rooflight?
- Why does my rooflight drip in winter?
- Does a rooflight need a vapour barrier?
- Can a rooflight be moved to a different part of the roof?
- Do you remove the old rooflight and dispose of it?
- Can rooflights be fitted in winter?
- How long does a rooflight installation take?
- What happens on installation day?
- How far in advance should I book?
- Do you need scaffolding to fit a rooflight?
- Cleaning and maintaining a rooflight
- How do you clean a rooflight you cannot reach?
Walk-On Rooflight Installation
20 answersQuestions
- What is a walk-on rooflight?
- Can you walk on a flat rooflight?
- How much does a walk-on rooflight cost?
- How strong is a walk-on rooflight?
- Are walk-on rooflights slippery?
- Can a walk-on rooflight be opened?
- Do walk-on rooflights need extra structure?
- Can you put furniture on a walk-on rooflight?
- Walk-on rooflights and where they make sense
- How thick is walk-on glass?
- Can a walk-on rooflight go in a driveway?
- Do walk-on rooflights scratch?
- Can you see through a walk-on rooflight from below?
- How do you clean a walk-on rooflight?
- Are walk-on rooflights safe for children?
- Do walk-on rooflights need a handrail?
- How long does a walk-on rooflight last?
- Can a walk-on unit replace a normal rooflight?
- Do walk-on rooflights leak?
- Glass floors and walkways explained
Conservation Rooflight Installation
20 answersQuestions
- What is a conservation rooflight?
- Can I put a rooflight in a listed building?
- Do I need permission for a rooflight in a conservation area?
- How much does a conservation rooflight cost?
- Are conservation rooflights double glazed?
- Do conservation rooflights open?
- What is the 150mm permitted development rule?
- Do you install rooflights on thatched roofs?
- Can a conservation rooflight be a different size?
- Conservation areas and listed buildings in Essex
- Permitted development limits for rooflights
- Do rooflights need planning permission?
- Who notifies building control about a rooflight?
- Do you handle the building control notification?
- Do I need building regulations approval for a rooflight?
- Can you fit a rooflight to a tiled roof?
- Rooflights in natural slate roofs
- Rooflights in plain clay tile roofs
- Rooflights in concrete interlocking tile roofs
- How close to the ridge can a rooflight go?
Sun Tunnel Installation
20 answersQuestions
- What is a sun tunnel?
- How much does a sun tunnel cost?
- How much light does a sun tunnel give?
- Can a sun tunnel go in a bathroom?
- How long does a sun tunnel take to fit?
- Can a sun tunnel be fitted to a flat roof?
- Do sun tunnels leak?
- How far can a sun tunnel run?
- Can a sun tunnel have a light in it?
- Do sun tunnels cause condensation?
- Sun tunnels and where they beat a rooflight
- Can a sun tunnel be fitted to any ceiling?
- Do sun tunnels need planning permission?
- What size sun tunnel do I need?
- Can a sun tunnel go through a loft conversion?
- Do sun tunnels lose heat?
- Can you fit a sun tunnel yourself?
- How do you clean a sun tunnel?
- Do sun tunnels work on a north facing roof?
- Can a sun tunnel be added to an existing hallway?
Ready to bring the daylight in?
Tell us about your project and we’ll send a clear, fixed written quote, no pressure, no surprises.
- Fixed written price before any work starts
- No pressure, no obligation, no sales calls
- Flexible survey times that suit you
- A reply within one working day