GUIDE · BUILDING SAFETY · Last reviewed August 2026
EWS1, cladding & high-rise flats: what affects your mortgage
Building height and construction era matter more than most buyers expect — here's what actually changes your lending options.
Since the Grenfell Tower tragedy in 2017, lenders have become significantly more cautious about taller buildings, cladding, and fire safety more broadly. Two separate things are worth understanding: the EWS1 process, and a much simpler, older rule around building height that catches many buyers by surprise.
What EWS1 actually is
An EWS1 (External Wall System) form is a fire-risk assessment of a building's external walls, used to confirm whether cladding or other materials present a safety risk. Many lenders require one for buildings above 18 metres (roughly six storeys) or where cladding is present, though some will proceed without one if the building has otherwise been assessed as low-risk.
The Building Safety Act 2022
Qualifying leaseholders are protected from remediation costs under this Act, and buildings five storeys or higher (over 11 metres) fall under stronger regulatory oversight, including a registered "Accountable Person" responsible for compliance. Ask specifically whether the building is registered and compliant — lenders increasingly check this before offering.
The five-storey rule — a separate, older issue
Independent of EWS1 and cladding, many lenders have a long-standing policy specifically for ex-local-authority flats and maisonettes: they simply won't lend on blocks above five storeys, regardless of the building's safety certification. This isn't primarily about fire safety — it's about resale risk, maintenance cost, and the practicalities of servicing lifts and communal areas in larger blocks.
- Several major lenders define "five storeys" as a ground floor plus four floors above, excluding basements
- Some lenders will consider taller blocks in cities like London, subject to a full survey — but this is the exception, not the default
- Deck access (external walkways serving each flat) is often treated as an additional risk factor on top of height, regardless of storey count
- This restriction applies specifically to former local-authority stock — privately built high-rises are assessed differently, primarily through the EWS1/cladding process above
What to check before offering
- How many storeys the block actually has, and whether it was originally local-authority or privately built
- Whether an EWS1 form exists, or whether the lender you're considering requires one for this specific building
- Whether the building is registered under the Building Safety Act, if it's five storeys or higher
- Whether there's deck access, which some lenders treat as a separate risk factor
Factor this into your numbers
Homabu's Precise calculator flags high-rise and ex-local-authority restrictions automatically.
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