Non-standard construction means a house is not built from traditional brick or block masonry. In the UK that usually means concrete panel or system-built, no-fines concrete, steel framed or timber framed. These properties can be perfectly sound, but they fail in different ways to masonry, so they need a Level 3 survey from someone who knows what to look for, and lenders assess them more carefully.
What to hold onto
Non-standard does not mean defective. It means a different structure with a different set of risks.
Many of these homes look like ordinary brick houses from the street, particularly once rendered.
Concrete carbonation and reinforcement corrosion are the defects that matter most.
Establish the construction type and lending position early, because it shapes everything that follows.
Which construction types are we talking about?
Concrete panel and system-built housing was produced in large numbers in the decades following the Second World War, when the priority was building quickly. Precast concrete components were manufactured off site and assembled on site, often with a steel or concrete frame. There were many proprietary systems, and they vary considerably in how well they have lasted.
No-fines concrete is a distinct and often misunderstood type. The mix deliberately omits the fine aggregate, so instead of dense concrete you get a lightweight, porous material full of interconnected voids. It was poured in situ into formwork and almost always rendered externally. It performs reasonably well when the render is sound, and it is very unforgiving of a render that is cracked or has been sealed with the wrong material.
Steel framed houses use a load bearing steel skeleton with infill panels or a masonry outer skin. Timber framed properties are common, generally sound and still not masonry, so the same principle applies: the structure behaves differently and needs assessing on its own terms. A Level 3 building survey is designed for exactly these unconventional builds.
What is concrete carbonation and why does it matter?
This is the central technical issue with reinforced concrete housing, and it is worth understanding properly because it explains most of what a surveyor is looking at.
Fresh concrete is strongly alkaline, and that alkalinity chemically protects the steel reinforcement embedded within it, holding it in a passive, non corroding state. Over decades, carbon dioxide from the air penetrates the surface and reacts with the concrete, gradually lowering its alkalinity. That process is carbonation, and it advances slowly inward from the face.
Once the carbonated zone reaches the steel, the protection is gone. Moisture and oxygen can then corrode the reinforcement. Corroding steel occupies considerably more volume than sound steel, so it exerts pressure from inside the concrete, cracking it and eventually blowing the surface off. That is why the visible signs are so characteristic: cracks running in straight lines that trace the reinforcement below, rust coloured staining, and spalled patches where the cover has detached.
The depth of cover over the steel is critical. Generous, well compacted cover carbonates slowly and protects the steel for a long time. Thin or poorly compacted cover, which happens on any construction programme run at speed, carbonates far sooner. That is precisely why two houses of the same system and the same age can be in genuinely different condition.
What does the surveyor examine?
Identify the system first
Establishing what the house actually is drives everything else, because known systems have known weaknesses. Render, cladding and later alterations can disguise the construction, so age, form, wall thickness and detailing all get read together.
Concrete surfaces and joints
Cracking patterns, spalling, rust staining and the condition of joints between panels. Joint seals have a finite life, and a failed seal lets water into the structure where it does the most harm.
Hidden frame elements
Steel members concealed within walls cannot be inspected directly, so the surveyor looks for the symptoms of corrosion nearby and recommends opening up where the evidence warrants it.
Render and moisture behaviour
Whether the render is sound, whether it is doing its job, and whether it is trapping moisture rather than shedding it. On no-fines walls this is the single most important external element.
Previous repairs and retrofits
Patch repairs in incompatible materials, and insulation added without regard to how these walls handle moisture, can create problems rather than solve them. Documentation for past work is genuinely valuable here.
Will a lender agree to a mortgage?
Often yes, though with more scrutiny than on a masonry house, and it varies by lender and by system. Some lenders decline particular systems outright. Others will lend subject to a satisfactory structural report, or on a reduced loan to value, or after specified remedial work.
The practical advice is to establish the construction type before you get deep into a purchase, and to talk to your broker about it early. Discovering the position after your offer is accepted and the chain is forming is what turns a manageable issue into a collapsed transaction. Our buying a home guidance covers how the survey levels differ, and every report is produced by an RICS registered surveyor, which is what lenders and solicitors want to see.
Questions worth asking before you offer
What is the construction type, and is there any documentation naming the system?
Has any structural repair or reinforcement work been carried out, and is it certificated?
When was the render last renewed, and in what material?
Has insulation been added, where, and using what specification?
Has the current owner had any difficulty with lending or insurance on the property?
Background on the different house types found across the UK housing stock is published by the English Housing Survey on gov.uk, and the professional standards governing how surveyors inspect and report on unconventional construction come from the Royal Institution of Chartered Surveyors.
Frequently asked questions
How can I tell if a house is non-standard construction?
Not always from looking, which is the difficulty. Clues include a build date in the decades after the Second World War, fully rendered walls with no visible brickwork, unusually smooth or flat wall surfaces, regular vertical joint lines under the render, and wall thicknesses that do not match cavity masonry. The estate agent particulars and the title documents sometimes name the system. A surveyor will identify it definitively.
Are these houses safe to live in?
The great majority are, and many have performed well for decades. The concern is not sudden failure but progressive deterioration that goes unmonitored. Where carbonation has reached the reinforcement and corrosion is advancing, it needs assessing and addressing rather than ignoring. Identified early, these are managed engineering problems with established repair techniques behind them.
Can concrete deterioration be repaired?
Yes, and concrete repair is a specialist field in its own right. Approaches include cutting out contaminated concrete and treating or replacing the reinforcement, applying repair mortars designed to restore alkalinity, and in some cases cathodic protection to arrest corrosion electrically. The right approach depends on the extent and cause, which is why diagnosis precedes any repair specification.
Should I insulate a no-fines concrete house?
Possibly, but not generically. No-fines walls are porous and rely on being able to dry out, so adding an impermeable insulation layer can trap moisture within the structure and move the dew point somewhere harmful. Any insulation strategy needs to suit the wall type specifically. This is one of those measures where a standard installation designed for cavity masonry can create a new defect.
Do I need a structural engineer as well as a surveyor?
Sometimes, and the survey will tell you. A Level 3 survey establishes the construction, identifies the defects and explains the likely causes. Where structural adequacy needs calculating, or where a lender specifically requires it, an engineer’s report follows. Working in that order is more efficient, because the survey defines what the engineer needs to examine rather than starting from nothing.
Does non-standard construction affect resale?
It narrows the buyer pool, because some purchasers cannot get lending on certain systems and others are put off by the label. That is usually reflected in the price you pay going in, so it is not automatically a bad purchase. What helps considerably at resale is holding good documentation: the survey, any structural reports and certificated evidence of repairs carried out.
Knowing what you are buying
Non-standard construction is a description, not a verdict. Plenty of these homes are sound, well located and sensibly priced. What you cannot afford to do is treat one as though it were an ordinary brick house.
If you are considering a concrete, system-built or steel framed property in Liverpool or across the North West, talk to Trust Surveyors before you commit.