External wall insulation · Mid Glamorgan
External wall insulation in Merthyr Tydfil
Quotes for external wall insulation in Merthyr Tydfil list the system, the detailing and the VAT position in writing, so you know exactly what's included. We plan EWI in Merthyr Tydfil around the details that cause trouble later — cills, eaves, downpipes and the base of the wall above the damp-proof course.
- Free survey in CF47 and nearby
- Guide price from £105 per m² + scaffold, 0% VAT
- Fixed written price before work starts
Free survey in Merthyr Tydfil
Postcode, service and a phone number is all we need.
What's included
- Boards chosen for the wall: EPS, mineral wool, wood fibre or phenolic
- Installing wall insulation in homes is currently zero-rated for VAT until 31 March 2027
- Covers tired brick, pebble dash or failing render with a new finish
- Typically takes a 225mm solid brick wall from around 2.1 W/m²K to about 0.30 W/m²K with 90–110mm of board
Local considerations in Merthyr Tydfil
We cover Merthyr Tydfil and nearby Aberdare, Rhondda and Ebbw Vale. It's roughly 7 miles from Merthyr Tydfil to Rhondda, the largest town in Mid Glamorgan. South Wales has long runs of solid-wall valley terraces, Victorian and Edwardian town housing and post-war council estates.
Parts of Mid Glamorgan fall in the higher wind-driven rain exposure bands, especially coastal and upland sites, so render specification, movement joints and detailing at cills, verges and the base of the wall matter more than usual.
For homes in Merthyr Tydfil, the survey starts with the wall itself: solid brick, stone or concrete, and whether any old render is sound enough to insulate over.
- Postcode district
- CF47
- County or area
- Mid Glamorgan
- Nation
- Wales
- Nearby
- Aberdare, Rhondda, Ebbw Vale, Pontypridd
Planning and building control in Wales
For homes in Merthyr Tydfil, the local planning authority decides any borderline cases; changing a brick house to render, or work on flats, usually needs an application in Wales.
In Wales, insulating or re-rendering more than half of a wall's area is treated as renovating a thermal element under Approved Document L (Wales), so building control is involved before work starts.
How does external wall insulation work?
Heat moves out through a wall faster when the wall is solid or poorly insulated. EWI wraps the outside face in a continuous layer of insulation, so the masonry stays on the warm side and the cold bridges at floor and party-wall junctions are reduced. The boards are bonded with adhesive and, on most walls, mechanically fixed. A base coat with an embedded glass-fibre mesh goes over the top, then a primer and the decorative finish.
Because the wall itself sits inside the insulation, it stays warmer and drier, and the rooms keep their full size. That is the main difference from internal insulation.
External wall insulation prices in Merthyr Tydfil
| Item | Guide price | Notes |
|---|---|---|
| EPS system with silicone render | £105–£145 per m²0% VAT | Most common choice for houses |
| Mineral wool system | £125–£170 per m²0% VAT | Non-combustible, vapour-open |
| Brick-slip finish over insulation | £185–£260 per m²0% VAT | Where a brick look is wanted |
| Three-bed semi, EPS + silicone (incl. scaffold) | £10,200–£17,7000% VAT | 80–100 m² of wall; depends on detailing and access |
Confirmed by a fixed written quote after survey. 0% VAT: installing insulation in a home is zero-rated until 31 March 2027, so these figures are the total; 5% applies from 1 April 2027.
How it works
Tell us about the property
Use the quote tool or form, or call. Photos help.
Free survey
We measure, check the walls and confirm approvals.
Fixed written quote
System, details, access, exclusions and VAT in writing.
Installation
Scheduled for suitable weather, with a clear programme.
External wall insulation in Merthyr Tydfil: questions
Does EWI need Building Regulations approval?
In England and Wales, usually. Insulating more than half of a wall's area, or more than a quarter of the building's whole external envelope, counts as renovating a thermal element, so building control needs to be involved and the wall should reach about 0.30 W/m²K where that's practical. Scotland and Northern Ireland have their own building standards processes.
Does external wall insulation cause damp?
Not when it is specified and detailed properly. Problems usually come from poor detailing: no starter track above the damp-proof course, gaps at cills and penetrations, or a vapour-closed system on a wall that needs to breathe. The survey checks moisture, ground levels and the wall type before a system is chosen.
How long does external wall insulation last?
A well-installed render system is commonly expected to last 25–30 years or more, with occasional cleaning and inspection of sealants. The system manufacturer's documentation states the expected service life for the specific build-up.
Do you cover Merthyr Tydfil?
Yes — we survey and quote external wall insulation in Merthyr Tydfil (CF47) and nearby Aberdare, Rhondda and Ebbw Vale, with a fixed written price before any work starts.