What Exactly is No Fines Concrete & Why Use it To Build Houses?

In Simple Terms, No-Fines Concrete is a concrete mixture that contains no sand or ‘fine’ aggregates which are commonly referred to as, ‘Fines’, but before moving forward, it helps to understand what standard concrete contains.

Standard Mix Concrete

Image Credit Concretepanels.co.uk

Standard concrete contains a mix of coarse aggregate (gravel), fine aggregate (sand) and cement.
Water is added to the mix before it is poured. After pouring, the wet concrete will normally be vibrated or tamped down to remove any air gaps or voids in the wet mix. This causes the sand and smaller fine particles to fill any gaps between the larger pieces of gravel. The mix will then set to form a dense mass of heavy, solid concrete, without visible air holes or pockets. Standard concrete containing fines, is laterally much stronger than no fines concrete.

No-Fines Concrete

No Fines Concrete

No-fines concrete (NFC), is an open formed cellular concrete, but unlike standard concrete, no fines (fine aggregates) or sand, is added to the mix. Research in the 1950s suggested that the use of NFC in construction would provide attractive savings to the construction industry, particularly in relation to energy and reduced cement costs. At the time, NFC was considered to be a product that could revolutionise affordable home building. Today though, those views have changed considerably, and many now argue, that in today’s climate of ever-increasing energy prices for consumers, NFC homes provide poor thermal performance, with an increased likelihood that many occupants will reach the point of fuel poverty, as heating expenditure rises, whilst income falls.

Fuel poverty in England is measured using the Low Income Low Energy Efficiency (LILEE) indicator. Under this indicator, a household is considered to be fuel poor if: they are living in a property with a fuel poverty energy efficiency rating of band D or below, and when they spend the required amount to heat their home, they are left with a residual income below the official poverty line.

There are 3 important elements in determining whether a household is fuel poor:
Household Income
Household Energy Requirements
Fuel Prices

Facts – No Fines Concrete

  • No-fines Concrete was first used in Europe in the 1800s because concrete was cheaper without the added fines.
  • It is estimated that over 300,000 No-Fines Concrete (NFC) dwellings were built across the UK in the 30 years between 1950-1980 alone.
  • In Scotland, there are estimated to be over 33,000 No-fines Concrete dwellings.
  • It was used extensively after WWII, due to severe shortages of materials and cement.
  • The concrete is generally constructed using 10-20 mm aggregate, but no aggregate below 10-mm is used.
  • No-Fines Concrete dwellings were initially viewed as being thermally efficient, however in comparison to modern standards, they offer poor thermal performance with increased risk of fuel poverty.
  • The majority of NFC Dwellings in the UK were constructed in the Social Housing Sector by Local Authorities.

No-Fines Concrete in construction

  • When set, NFC contains many air pockets, which depending upon wall thickness, and inner wall lining, can provide a thermal rating similar to or better than that of a traditional, uninsulated, brick cavity wall.
  • NFC is sometimes referred to as; Porous Concrete, Pervious Concrete or Permeable Concrete.
  • It is generally mixed at a ratio of 6/7 parts aggregate to 1 part cement.
  • No-Fines Concrete is lighter than standard concrete and therefore easier to handle if required.
  • It requires moderate rodding and minimal compaction during casting. Unlike traditional concrete, it does not require significant vibration to remove trapped air.
  • The height at which NFC was dropped into casting moulds determines the level of compaction and also dictates the size and quantity of air voids in the cured structure.
  • No-Fines Concrete can be used to build relatively tall walls, without increased the size of footings excavation.
  • The shape of the aggregate used during mixing, influences the void sizes within the cured concrete.
  • No-Fines Concrete Walls up to 7.5 metres high and 18 metres long were recording in some housing structures.
  • During the Inter-War and Post-War years, there were no set standards for NFC in house building, hence the quality of the finished concrete in use, varies considerably depending upon the level of workmanship.
  • No-Fines Concrete is not suitable for use in reinforced concrete applications.

What is a No-Fines House

wimpey no fines house
Wimpey No-Fines House – Watermarked in Our Former Domain Name

The No-fines method of house construction was used extensively between the 1920s, right through to its peak in the 60’s & 70s. It offered a much faster, cost-efficient method of house building, that also employed fewer skilled bricklayers and associated tradesmen than traditional methods. Instead of having to construct labour-intensive, masonry brick walls, heavy-duty metal/timber framework or formwork as it’s often referred, was created to form large panel or slab moulds, into which freshly mixed No-Fines concrete was poured. Once sufficiently set, the boards were removed and once the concrete had sufficiently cured and dried, cement render was applied to the exterior face, and wet plaster to the interior. Externally, a typically rendered No-Fines House can virtually indistinguishable to that of a traditional brick rendered dwelling. To the untrained eye, it is usually only possible to reliably identify the construction type, after inspecting the exterior walls above eaves level, from the roof-space void.

wimpey no fines house under construction
The Impressive Amount of Formwork Required To Build a No-Fines Concrete House

It is not uncommon for prospective purchasers of No-Fines houses to be surprised to hear that their chosen property was not constructed from brick,

The most prolific builder of No-Fines housing in the UK, was a company called George Wimpey and Co. Ltd. They built over 300,000 ‘Wimpey No-Fines’ houses of varying design variations between the 1940s and 70s. Commonly referred to as ‘Wimpey No-Fines’, their product variations included names such as Butterfly, Butterfly No-Fines, Formwall, Gateshead Butterfly, Gateshead No-Fines, No-Fines Wimpey and the Wimpey W6M. The pure breadth of design styles that Wimpey went on to produce is quite astonishing, but at the same time, it also serves to make manufacturer identification rather difficult. There were of course a number of other companies that built homes using “no-fines concrete”, and these do vary quite wildly from region to region.

Quite often, No-Fines properties are generically labelled as “Wimpey No-Fines”, when in fact other companies produced named dwelling systems including, but not limited to: Farrans No-Fines -1000 built, Miller No-Fines, SSHA No-Fines -500 built, Unit No-Fines -4350 built, Weir No-Fines -100 Built.

Non-Traditional Label

All types of No-Fines houses are classified as being of Non-Traditional or Non-Standard Construction, simply due to the use of the Non-Traditional materials and methods during construction.

The term, ‘Traditional Construction’ in the U.K. refers to any dwellings or buildings constructed primarily from traditional building materials such as Cob, Brick or Stone. Any property constructed of materials outside this remit, such as concrete, steel framed, timber framed etc, fall into the category of Non-Traditional Constructions.

The term Non-Traditional Construction, when applied to housing, does not automatically mean that all Non-Traditional properties are defective. In reality, there are only a relatively small number of Non-Traditional UK dwellings that were classified as defective under the Housing Defects legislation of 1984. The affected houses were constructed from Precast Reinforced Concrete (PRC), which is quite different to NFC, so don’t make the mistake of thinking all Non-Trads are defective and non-mortgageable.

Prospective Buyers

Of course, certain construction types have their own specific issues and faults, and this is equally so in both Traditional and Non-Traditional constructions.

If you’re looking to purchase a No-Fines property, you should always carry out due diligence and employ the services of a RICS Structural engineer to inspect and survey the property. Don’t simply rely on a basic homebuyers survey, as this will offer you virtually no protection should things go wrong later.

You should also ensure that you approach the right mortgage provider when looking to purchase a house of Non-Traditional Construction, because not all lenders provide mortgages for this category of property. Always check the mortgage provider’s published lending criteria, before you make an application. It could save you a considerable amount of money.

No-Fines Concrete – Performance In Use

The Building Research Establishment (BRE) list several points that surveyors should be aware of in relation to No-Fines Concrete properties, it is important to understand that faults can and sometimes do arise with this property type.

  • Vertical cracking of no-fines concrete external walls.
  • Horizontal cracking of render above window drips.
  • Scarcity and corrosion of wall ties to brick cladding.
  • Low to high rates of carbonation of dense aggregate concrete ring beams.

The BRE have produced a far more in-depth report regarding No-Fines Dwellings which can be purchased from the BRE Bookstore. Please see the link at the bottom of this page, under the heading further reading.

Thermal Heat Transfer

Despite having a relatively good history of structural performance compared to other concrete construction systems, No-Fines dwellings can also suffer from significant heat loss through uninsulated external walls. Investigations carried out by the Building Research Establishment (BRE) using FLIR thermal imaging cameras, provides a sobering insight as to the thermal performance of a number of No-Fines dwellings.

The images were taken in February 2010, with an outdoor temperature of 8° C. All the target houses were occupied and internally heated.

The warmer colours show heat escaping through the walls, with white being the hottest, then red, orange, yellow, green, blue and black being the coldest.
The blue colour around window and door frames indicates the likely presence of cold bridging.
Cold bridging is caused when an element in the structure or building fabric becomes cold and the cold temperature transfers through the medium from the outside of the building, to the considerably warmer interior. This is known as Cold Bridging, where part of a structure acts a bridge, but instead of carrying pedestrians into a building, this bridge carries or rather transfers the cold from the outside, into the inside of the house.
One of the problems associated with cold bridging, is the risk of condensation forming on the internal cold face of the bridge element once it connects with the warm interior air inside the house.
When warm air, meets a cold surface, moisture in the warm air condenses on the cold surface, causing condensation. Sometimes, entire walls can act as a cold bridge, which can lead to extensive damp and mould issues inside a room or building, but in the case of a No-Fines Concrete house, much would depend upon the thickness of the wall, the number and size of air pockets present in the structure, and the type and condition of internal and external wall linings fitted to the property, including interior plaster, plasterboard or internal insulation on the inside, and render, external wall insulation, brick slips etc on the outside.

External Wall Insulation

No-fines houses can be externally insulated and make good candidates for EWI insulation systems.

Do you live in or have experience with the No-Fines Concrete house?

If you do, then please share your thoughts and opinions in the comments section below. We’d also be interested to hear of your memories of growing up and living in these homes.

Further Reading

The Structural Condition of Wimpey No-Fines Low-Rise Dwellings (BRE Bookshop Price £30)