Timber Dormer Windows
Engineered hardwood or softwood — the right answer on period and listed roofs. Slim sightlines and a profile a conservation officer will accept.
Timber Dormer Windows — indicative geometry
What a timber dormer window actually is
Timber gives you the narrow sections and the moulded detail that period roofs need, and modern engineered laminated stock is dimensionally far more stable than the solid softwood it replaced. Factory-applied microporous paint or stain gives 8–10 years before recoating. On a front elevation in a conservation area it is very often the only material that will be approved.
Specification at a glance
| Timber | Engineered laminated softwood or hardwood |
|---|---|
| Finish | Factory microporous paint or stain |
| Repaint interval | 8–10 years |
| Sightlines | Slimmer than uPVC or aluminium |
| Glazing | Double or slim-profile heritage units |
| Guarantee | 10 years, finish 8 years |
How we build it
We would rather tell you at survey that your ridge height will not take what you want than take a deposit and find out in week three. Every timber dormer windows job runs the same seven stages — survey and feasibility, design and consent, scaffold and protection, structure, weatherproofing, glazing, then finish and sign-off.
Rear dormers on houses often sit inside permitted development, but the volume allowance is consumed by any previous loft or rear extension — so we check the planning history for the address before we say yes.
What is included in the price
- Measured survey, structural calculations and full working drawings
- Planning application or lawful development certificate, and the building regulations application
- Scaffold design, erection, weekly inspection, hire and dismantling
- All structure, weatherproofing, flashings, gutters and cladding
- Glazing with escape-compliant opening lights where required
- Building control inspections and your completion certificate
- Waste removal and making good
Where this goes wrong elsewhere
The two failures we are called to fix most often on timber dormer windows are undersized or incorrectly lapped flashings, and a vapour control layer that stops at the first awkward junction. Neither shows up for a winter or two. Both are cheap to do properly at build stage and expensive to correct afterwards.
Send us the address and roughly what you are hoping to gain, and we will come back with a realistic answer rather than an optimistic one.
Related work
Timber Dormer Windows by county
Where we do this work
Specialist teams across 74 counties. Pick your area for local detail, or browse every town.
How a dormer gets built
Seven stages, in this order, every time
The sequence matters. Most dormer problems come from doing one of these out of order — glazing before the flashings, or opening the roof before the materials land.
Survey and feasibility
A specialist measures the roof, checks ridge height, span and structure, and confirms whether you are inside permitted development.
Design and consent
Measured drawings, elevations and sections. We submit the planning application or lawful development certificate and the building regulations application.
Scaffold and protection
Scaffold designed, erected and inspected. Temporary weather protection over the work area before anything is opened.
Structure
Ridge beam and floor steels craned or manhandled in, new joists laid, the dormer frame built and sheathed.
Weatherproofing
Deck, insulation, membrane or lead, cheek cladding, flashings and gutters — the dormer is weathertight from this point.
Glazing
Windows fitted square, sealed and drained, with escape-compliant opening lights where required.
Finish and sign-off
Plaster, electrics, decoration and making good, final building control inspection and your completion certificate.
FAQs
Timber Dormer Windows — your questions
Will a dormer add value to my house?
A properly built and signed-off dormer conversion adding a bedroom and bathroom typically returns a meaningful share of its cost in value, and more in areas where floor space is scarce. The building control completion certificate is what makes the space count as habitable floor area on a valuation — without it, surveyors will not include it.
Can you match my existing roof tiles?
Usually. Most common clay and concrete profiles are still in production or available reclaimed, and we source a match at survey stage so you see it before work starts. Where a discontinued profile cannot be matched exactly, we normally recommend taking tiles from a less visible slope for the dormer and using the closest new match on the hidden elevation.
What is the difference between a dormer and a Velux?
A rooflight sits flush in the roof slope and gives you light without any extra height — you still have a sloping ceiling. A dormer projects out from the roof and creates vertical walls with a level ceiling behind them, so you gain genuinely usable standing space and floor area, not just daylight.
How wide can a dormer be?
Structurally, as wide as the roof — full-width rear dormers regularly run six to eight metres, carried on a steel ridge beam. The limits are usually planning volume allowances and the setbacks needed at eaves and ridge, rather than what can be built.
How disruptive is a dormer build?
Less than people expect, because most of the work happens above your ceilings and is reached from the scaffold. The noisy phases are opening up and installing steels, typically two to four days. Once the staircase is cut in there is dust and traffic through the house, and we sheet and protect the route for that period.
Can a dormer include an en-suite?
Very often, yes — a full-width or L-shaped dormer usually has enough floor area for a bedroom plus a shower room. The practical constraints are getting soil and waste down to an existing stack, and whether the head height over the shower tray works. Both are settled at survey.
Can you build a dormer in winter?
Yes, with adjustments. Temporary weather protection over the scaffold lets structural work continue in most conditions. GRP roofing needs dry conditions above about 5°C to cure properly, so in a cold spell we either sequence it differently or specify EPDM, which is unaffected.
Find out what your roof will take
A free measured survey tells you what is achievable, what it needs, and what it costs — before you commit to anything.