Quick answer: With us, loft insulation in Cardiff starts from £600 installed, using Knauf Earthwool mineral wool topped up to 270mm. The final price depends mainly on the size of your loft, how much insulation is already there, how easy the loft is to get into and work in, and if you also want boarding or old insulation taken out. We confirm the exact figure after a free survey.
Prices on the internet are hard to trust because every loft is different. A small 1930s semi in Whitchurch with 100mm of old rockwool is a very different job from a large Victorian terrace in Roath with nothing up there but stored boxes and a broken hatch. So rather than give you a made-up average, this guide sets out our own starting prices and explains exactly what moves a quote up or down.
Our loft insulation prices in Cardiff
These are our installed "from" prices. They include materials and labour. The figure you are quoted will be the same or higher depending on the factors further down this page.
| Service | Installed price | Notes |
|---|---|---|
| Loft insulation (Knauf Earthwool loft roll) | From £600 | Typically topped up or installed to 270mm |
| SuperFOIL multifoil insulation | From £800 | Fitted to the rafters; suits lofts used for storage or as rooms, low pitches and awkward spaces |
| Loft boarding | From £500 | Boards raised on loft legs so the insulation underneath isn't squashed |
| Rodent proofing | From £250 | Inspection, sealing entry points, mesh, replacing contaminated insulation |
| Loft mould treatment | From £300 | Fungicidal treatment plus fixing the cause |
| Metal loft ladders | Priced after survey | Depends on hatch size, ceiling height and whether the hatch needs altering |
| Spray foam insulation removal | Priced after survey | Depends on roof area, foam type and the condition of the timbers |
For a national comparison, the Energy Saving Trust publishes its own typical installation costs for a standard home in Great Britain, which you can see on its roof and loft insulation page (linked in the sources below). Treat any national figure as a rough guide only, because it can't account for the access, clearing and removal work that often makes up a big part of a real quote.
What affects the cost of insulating your loft
1. The size of the loft
The biggest single factor is floor area, because it sets how many rolls of insulation we need and how long the job takes. A two-bed terrace and a detached four-bed are not priced the same. We measure the loft on the survey rather than guessing from the outside of the house, because extensions, hipped roofs and chimney breasts all change the usable area.
2. How much insulation is already there
Most Cardiff lofts we see already have something. If there is a decent, dry layer of 100mm or so between the joists, we can usually top it up with a cross-laid layer to reach 270mm, which costs less than starting from bare joists. If there is nothing at all, you need the full depth. We can check the depth and condition of what you have on the survey.
3. Removing old insulation
Sometimes the existing insulation can't stay. It might be damp, flattened, soiled by mice or rats, or full of debris. Taking it out, bagging it and disposing of it properly adds labour and disposal cost. If rodents have been in, we will usually recommend rodent proofing at the same time, otherwise the new insulation ends up in the same state.
4. Clearing the loft
We can only lay insulation on floor we can reach. If the loft is full of stored belongings, you can either clear it before we arrive or we can quote to move things for you. Clearing it yourself is the easiest way to keep the price down.
5. Access and working space
A good-sized hatch and a decent amount of headroom make for a quicker job. A tiny hatch, a very low pitch, a loft with no light, or a long, narrow roof space behind dormers all slow things down. Low-pitched roofs are one of the cases where SuperFOIL fitted to the rafters can be a better fit than trying to lay thick rolls across the joists.
6. Boarding for storage
If you want to keep using the loft for storage, boarding goes on top of the insulation. Boards should never be laid straight onto 270mm of insulation, because that squashes it and cuts its performance. We raise the boards on loft legs, which is why boarding is priced as a separate service from £500. More on that in our guide to boarding a loft without crushing the insulation.
7. The hatch and ladder
An uninsulated, draughty hatch lets warm air straight into the cold loft. We can insulate and draught-strip it as part of the job. If you are fed up with a stepladder, we also supply and fit aluminium folding and sliding loft ladders, including hatch alterations where needed. Because hatch sizes and ceiling heights vary so much, we price these after seeing the space.
8. Other work that needs doing first
Insulating over a damp or mouldy loft just traps the problem. If we find signs of condensation, mould, roof leaks or rodent activity, we will tell you on the survey and explain what needs sorting first and what it costs. The Energy Saving Trust gives the same advice: if you have damp in your loft, get professional advice before insulating.
What is included in our price
- A free survey of the loft, including a check for damp, ventilation and anything that needs attention first
- A written quote, usually back to you within 24 hours
- Knauf Earthwool loft roll laid between and across the joists to the agreed depth
- Keeping eaves ventilation clear so the roof space can still breathe
- Insulating around pipes and the cold water tank where needed, without insulating directly under the tank
- Tidying up and removing our waste at the end of the day
Most standard loft insulation jobs are completed in a single day.
How to keep your quote down
- Clear the loft yourself before the installation day, or at least the areas being insulated.
- Do the work together. If you are planning insulation and boarding, or insulation and a new ladder, doing them on the same visit avoids paying for two call-outs.
- Keep what is still good. We don't strip out dry, decent insulation just to make the job bigger. If it can be topped up, we will say so.
- Sort problems once. Fixing a ventilation or rodent issue at the same time as insulating is cheaper than coming back to redo it later.
Are there grants for loft insulation in Wales?
Some households can get help with the cost of insulation through government-backed schemes, but eligibility depends on things like income, benefits and the energy rating of the home, and the schemes change. We cover the current position in our separate guide to loft insulation grants in Wales on the advice hub. If you aren't eligible, our standard prices above apply.
Getting an accurate price
The only way to get a figure you can rely on is for someone to look in the loft. Our surveys are free and there is no obligation, and you can read more about how we fit it on our loft insulation service page. We will measure up, check what is there, tell you honestly whether a top-up, full install, SuperFOIL or a combination makes most sense, and send a written quote, usually within 24 hours. You can call us on 0800 229 4668 or request your free quote online.