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This page brings together answers to 36 common questions about suitability, pricing, process, materials, guarantees, and what to expect before booking a survey.
About External Wall Insulation
External wall insulation (EWI) involves fixing insulation boards to the outside of your walls, then covering them with a protective render finish. It keeps heat in, reduces energy bills, and transforms your home's appearance.
Significantly warmer. Customers typically describe the change as dramatic: walls that were cold to touch become warm, rooms that never heated properly become comfortable, and many report a 25-40% reduction in heating costs.
Yes, usually. Condensation happens when warm air meets cold walls. When your walls are properly insulated, they stay warm on the inside, so condensation stops forming. This also helps prevent the mould that comes with condensation.
Yes. External insulation can be added to solid walls, cavity walls, and even walls that already have cavity insulation. It adds an extra thermal layer and completely transforms the appearance.
No. Unlike internal insulation, external wall insulation is added to the outside of your home, so your internal room sizes stay exactly the same.
Properly installed external wall insulation using quality materials typically lasts 25-30 years or more. The insulation itself does not usually degrade; the render finish may need attention eventually, but we are talking in decades rather than years.
Usually not. External wall insulation is typically permitted development. However, if you are in a conservation area, have a listed building, or your property has specific restrictions, you may need approval. We advise on this during your survey.
About K Rend
K Rend is a brand of silicone render made by Kilwaughter Minerals. It is one of the UK's most popular external render products: hydrophobic, self-cleaning, breathable, and colour stable.
It is a proven, high-quality product that performs brilliantly on the older Midlands homes we work on. It offers excellent water resistance, good breathability, a wide colour range, and is backed by a 25-year manufacturer guarantee.
There are dozens of options, including whites, greys, creams, naturals, and more. We bring samples to your survey so you can see real options against your property. Grey is currently the most popular choice.
Usually yes. If you know the colour name, we can match it exactly. If not, we can often identify it from a sample or photo.
K Rend typically lasts 25 years or more with minimal maintenance. It is through-coloured, so it will not need painting, and its self-cleaning properties help keep it looking good.
Very little. There is no painting required. An occasional wash with a hose can keep it looking fresh, but even that is often unnecessary thanks to its self-cleaning properties.
Costs & Pricing
It depends on property size, complexity, access, and condition. Typical ranges are terraced £5,000-8,000, semi-detached £8,000-12,000, and detached £10,000-16,000 or more. We provide accurate quotes after surveying your specific property.
Because every property is different. A typical semi can vary hugely in wall area, complexity, and condition. We do not want to mislead you with from-prices that do not reflect reality. A survey gives you an accurate quote for your home.
We can discuss payment terms that work for you. Typically there is a deposit on acceptance and the balance is paid on completion, but we are flexible.
No. Our quotes include everything: scaffolding, materials, labour, and all finishing details. The price we quote is the price you pay.
For most owners of cold, solid-wall homes, yes. Energy savings can often cover the cost within 10-15 years, and you also get immediate benefits such as a warmer home, less condensation, and a transformed appearance.
The Process
We visit your property, assess your walls, discuss your requirements, show you colour samples, and answer your questions. It usually takes about 30-45 minutes. There is no charge and no obligation.
Usually within 2-4 weeks of accepting a quote, depending on our schedule.
An average property typically takes 2-3 weeks. Larger or more complex properties may take longer.
Yes, absolutely. The work is entirely external. There will be scaffolding and some noise, but you can live normally in the property throughout.
Scaffolding has to stand somewhere, so there is some impact. We take care to protect plants and surfaces, and any minor disruption is temporary.
We remove them before starting and refit them, or replace them if needed, once the render is complete. It is all included in our quote.
Yes, although very cold or wet weather can affect render application. We schedule work appropriately and keep you informed if weather causes delays.
About Rockwarm
Since 1985, which means more than 40 years of insulating Midlands homes.
Yes. We are based in Nuneaton and serve Coventry, Birmingham, and the wider Midlands. We are not a national franchise; we are a local family business.
No. Everyone who works on your property is employed by Rockwarm. We do not subcontract installation work.
Yes. We are TrustMark registered and BBA certified. We also work with housing associations and energy providers as approved contractors.
We believe grant schemes often give homeowners a worse deal: inflated costs, lower-spec materials, no choice of installer, and longer delays. We would rather give you a fair price for excellent work completed quickly. Read more about grants vs private.
Coventry, Nuneaton, Birmingham, and the wider Midlands, roughly a 30-mile radius from our Nuneaton base. If you are unsure whether we cover your area, just ask.
Call us. We stand behind our work and address any issues. We have been here for decades and we are not going anywhere.
Materials & Quality
We use Rockwool stone wool insulation as standard. It is breathable, fireproof, acoustically insulating, and better suited to older solid-wall homes than cheaper polystyrene systems.
Breathability is the main reason. Older homes need walls that can release moisture, and Rockwool allows this while polystyrene does not. Rockwool is also A1 fire rated and provides acoustic insulation. Learn more.
Typically 100-150mm, depending on your property and requirements. We recommend the most appropriate specification during your survey.
K Rend provides a 25-year manufacturer guarantee on the render. We also provide our own workmanship guarantee, and as a long-established local business we are here to honour it.

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