Internal wall insulation · Wales
Internal wall insulation in South Glamorgan
Get guide prices online, then a free survey and fixed quote for internal wall insulation in South Glamorgan, including Barry and Penarth. For terraced homes in South Glamorgan with attractive brick fronts, one approach is to insulate the front internally and the rear externally.
- Free survey and fixed written price
- Guide price from £75 per m² 0% VAT
- Planning and building control checked for Wales
Free survey in South Glamorgan
Tell us the postcode and what you need.
What's included
- Needs careful detailing at floor joists, reveals and corners
- Sockets, radiators, skirting and coving are moved and refitted
- Keeps the outside of the house exactly as it is
- Loses roughly 50–100mm per insulated wall
- Can be done one room at a time during a renovation
Local considerations in South Glamorgan
South Wales has long runs of solid-wall valley terraces, Victorian and Edwardian town housing and post-war council estates.
Exposure to wind-driven rain varies across South Glamorgan: sheltered town streets fare better than walls on high ground or facing the prevailing weather, and the render, beads and cill details are chosen with that in mind.
We plan internal insulation in South Glamorgan homes room by room so you keep the rest of the house usable.
- Nation
- Wales
- Region
- South Wales
- Towns covered
- Cardiff, Barry, Penarth
- Guide price
- From £75 per m² 0% VAT
Approvals in Wales
Internal insulation rarely needs planning permission, but in England and Wales insulating or replastering more than half of a wall's area involves building control, and listed buildings need consent for internal changes that affect their character.
The Building Regulations as they apply in Wales treat insulating or re-rendering more than half of a wall's area, or more than a quarter of the building's whole envelope, as renovating a thermal element, with Approved Document L (Wales) setting the target. Building control is involved before work starts.
Do I need Building Regulations approval?
Yes, in England and Wales once you insulate or replaster more than half of a wall's area (or more than a quarter of the building's whole envelope), it's treated as renovating a thermal element. The wall should reach about 0.30 W/m²K where practical, and building control needs to be involved.
Internal wall insulation prices in South Glamorgan
| Item | Guide price | Notes |
|---|---|---|
| Insulated plasterboard, supplied and skimmed | £75–£110 per m²0% VAT | |
| Insulated stud wall | £90–£130 per m²0% VAT | |
| Typical bedroom, one external wall | £1,795–£2,9950% VAT | Including making good |
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.
What happens next
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.
Internal wall insulation in South Glamorgan: questions
Can I stay in the house?
Yes, but each room is out of use while it's worked on, typically 3–5 days.
Is internal insulation cheaper than external?
Per m² usually yes, but the cost of moving fittings and redecorating narrows the gap on whole-house jobs.
How much room space will I lose?
Usually 50–100mm on each insulated wall, depending on the system.
Do you cover all of South Glamorgan?
Yes. We survey and quote internal wall insulation across South Glamorgan, including Cardiff, Barry, Penarth.
Do I need planning permission in Wales?
Permitted development rules for houses in Wales are similar to England's: a similar-appearance finish on a house is often permitted, while conservation areas, National Parks, Areas of Outstanding Natural Beauty, flats, commercial buildings and listed buildings need permission or consent. We check your address before quoting.