EWI Defects and TrustMark Find & Fix: Check Your Install

The external wall insulation scandal, in plain terms

If your home had external wall insulation (EWI) fitted through a government grant scheme, there is a real chance the work was not done properly. In October 2025 the National Audit Office published findings that around 98% of external-wall-insulation jobs installed under ECO4 and the now-closed Great British Insulation Scheme had defects of some kind. Not all of those defects are serious, but the scale of the problem was enough to trigger a national remediation response through TrustMark.

This guide explains what that means if it was your home, how the free TrustMark Find & Fix audit works, and how to avoid ending up with a bad install in the first place. It is written for homeowners and tenants, not installers, and everything here points you back to the official channels. As always with this site, we install nothing and run no scheme. Checking your install and requesting an audit is free.

What “defects” actually means here

External wall insulation wraps the outside of your home in an insulating layer and a weatherproof render. It is the most expensive common insulation measure, typically around £18,000 unsubsidised for a whole house, which is exactly why grant funding matters most for solid-wall homes. It is also the measure most likely to go wrong when installed badly, because it is a complex, skilled job that has to manage moisture, ventilation and detailing around windows, doors, roofs and the damp-proof course.

Defects found in the NAO review ranged from cosmetic to structural. Common problems include:

• Render cracking, blistering or coming away from the wall
• Missing or badly fitted beading, sealant and detailing around openings
• Inadequate provision for moisture to escape, which can trap damp inside the wall
• Insulation boards fitted below the damp-proof course, drawing moisture up
• Poor or absent ventilation to roof spaces and behind the system

Trapped moisture is the one to take seriously. Badly detailed EWI can cause damp and mould rather than curing it, so a job that “looks finished” is not the same as a job that is safe and durable.

The free TrustMark Find & Fix audits

Because so many installs were affected, TrustMark set up a Find & Fix programme to audit grant-funded external wall insulation and put right any faults, at no cost to the household. The principle is that the work was paid for under a government-backed scheme, was meant to meet the required standards, and so remediation is the industry’s responsibility, not yours.

You should consider requesting a Find & Fix audit if all of the following apply:

• Your home had external wall insulation fitted (solid-wall render systems, not cavity or loft insulation)
• The work was funded through a grant scheme — typically ECO4 or GBIS
• The installation was recent, broadly within the period the schemes have been running

To start the process, go to TrustMark{rel=“noopener” target=“_blank”}, which holds the register of accredited businesses and coordinates the Find & Fix scheme. You can search whether your installer is TrustMark-registered and follow the route to request an audit. If your original installer has since gone out of business, TrustMark and the scheme’s financial protection are designed to cover exactly that situation, so do not assume you have no recourse.

Two practical points. First, an audit is an inspection: it tells you whether there is a defect and what needs doing, and it does not commit you to anything. Second, be patient and go through the official channel — this is precisely the kind of situation cold-callers exploit, which we come back to below.

How to check your own install first

You do not need to be an expert to spot the warning signs before you request an audit. Walk around the outside of the house and look for cracked, bulging or discoloured render, gaps where the render meets windows, doors and the roofline, and any staining that suggests water is getting behind the system. Inside, watch for new patches of damp or mould on the internal face of external walls, condensation that was not there before the work, and a musty smell in previously dry rooms.

Also dig out your paperwork. A properly delivered grant-funded retrofit should have generated documents: a retrofit assessment, a design, and a completion certificate lodged with TrustMark. If your “installation” produced none of that, or the installer turned up, fitted a measure and left with no assessment at any stage, that is itself a red flag about how the job was managed.

Why bad installs happened: PAS 2035 and the retrofit assessment

Grant-funded insulation is not supposed to be a case of someone selling you a single measure off the back of a van. Since 2019, work under these schemes has had to follow PAS 2035, the retrofit standard, with the physical installation meeting PAS 2030. In practice that means a compliant job starts with a retrofit assessment of the whole home and is overseen by a qualified Retrofit Coordinator who considers ventilation, moisture and how measures interact, before anything is fitted.

The reason so many EWI jobs failed is, bluntly, that some installers treated the standard as paperwork to be rushed rather than a process to be followed. Skipping or faking the assessment, ignoring ventilation, and detailing the render badly are all breaches of what should have happened. Knowing this gives you a simple test for any future work: if an installer wants to fit a grant-funded measure without a retrofit assessment first, walk away.

Avoiding a bad install next time

Whether you are having your first solid-wall job done or replacing a failed one, the safeguards are the same. Use them alongside our fuller guides to solid wall insulation grants and how to apply.

Step	What to check	Why it matters
Accreditation	Installer is TrustMark-registered and works to PAS 2035/2030	Mandatory for grant-funded work; your route to redress if it goes wrong
Assessment first	A retrofit assessment happens before any measure is chosen	A measure sold without assessment is a warning sign
Written approval	Grant approval is confirmed in writing before work starts	Never start, and never pay upfront, without it
Paperwork	You receive assessment, design and completion documents	These lodge the job with TrustMark and enable Find & Fix
Verify the channel	Installer matches the scheme (obligated supplier for ECO4, council for the local grant)	Confirms the funding is genuine, not a cold-call funnel

You can read more about how these schemes are meant to work, and where the money comes from, on our grants and funding hub, and check what your household qualifies for using the eligibility checker.

The scam angle you must not ignore

A national remediation programme is a magnet for fraud. Expect cold calls, texts and doorstep sellers claiming they can “check your grant insulation” or offering a “free inspection” that quickly turns into a hard sell for more work or an upfront fee. Genuine schemes do not work like that. Real audits go through TrustMark, and real grant applications go through gov.uk, your council, an obligated energy supplier or an accredited installer.

Never pay upfront, never let anyone start work before written grant approval, and be especially wary of anyone pushing spray-foam loft insulation on the same visit — that is a separate, well-known mis-selling trap that can block mortgages. Our insulation grant scams guide covers the tactics in detail, and our page on whether “free” insulation is really free explains the honest picture behind the marketing.

What to do now

If your external wall insulation was grant-funded, start by inspecting the outside and inside of your walls and finding your paperwork. If anything looks wrong, or if you simply want certainty, request a Find & Fix audit through TrustMark{rel=“noopener” target=“_blank”} — it is free, and you are not committing to further work by asking. For an overview of the standard the work should have met, the Energy Saving Trust’s guidance on solid wall insulation{rel=“noopener” target=“_blank”} is a useful plain-English reference, and the current state of the funding schemes is set out on gov.uk{rel=“noopener” target=“_blank”}.

If you would rather talk it through before deciding, you can contact us or read the common questions on our FAQs page. We cannot inspect your walls or arrange the audit for you — that has to go through TrustMark — but we can help you understand where you stand before you pick up the phone.