This process covers all construction materials and products. One of the other key aims of the directive is to allow any products that existed before the implementation to be able to continue to do so. In time it is expected that European standards for products will take over from all national standards, for example British Standards (which will be phased out after a transitional period). The most visible sign of the new European Standards will eventually be the CE marking of all products. For the next few years at least, CE marking will not be a legal requirement of product trading within the UK and Ireland and it remains optional. However, H+H UK has taken the option to CE Mark, since it is the mark of conformity with our European standard and it denotes that our products satisfy certain requirements within European law.
New standard for aircrete blocks
BSI has published a new European standard for aircrete ‘masonry units’ (a combined term for bricks and blocks) being BS EN 771-4: 2003. For aircrete masonry units the old British standard, BS 6073-1: 1981 was withdrawn in April 2006.
Our factory production control systems have been assessed and certified by BBA for CE Marking purposes.
EN 771-4 is part of a series of product standards for different types of masonry unit. For example, clay bricks are covered and specified in accordance with Part 1 and aggregate concrete blocks with Part 3 of EN 771. There is also a new suite of test methods, most covered by the EN 772 series of standards, as well as new product standards for mortars, lintels, wall-ties etc. Our own brand of ‘Celfix’ thin layer mortar complies with EN 998-2, H+H UK has the documentation in place to CE Mark the product.
EN 771-4 specifies the characteristics and performance requirements for aircrete masonry units available throughout the CEN member countries. It aims to do so in product performance terms, avoiding as far as possible prescriptive requirements. The concept of the declared value has been introduced and is the value claimed by H+H UK for the various properties referred to in the standard. There are other notable differences between the new and old standards, in particular the supporting test methods are different and in respect of compressive strength. In addition, aircrete blocks can be designated either Category I or II. Celcon blocks are manufactured to a category appropriate to their intended use.
It should be noted that the declared value of a performance characteristic given for a masonry unit conforming to one part of EN 771 cannot always be directly compared with the same performance characteristic for a masonry unit conforming to another part of EN 771. This is particularly the case for compressive strength, where the test conditions vary considerably and this results in major differences in apparent strength across different types of bricks and blocks.
Scope of the European standard
The standard specifies the requirements for aircrete blocks for which the main intended uses are different types of load bearing and non-load bearing applications in all forms of walling including single leaf, cavity, partitions, retaining, basement and general use below ground level. It also includes walling for fire protection, thermal insulation, sound insulation and the fabric of chimneys (excluding chimney flue units).
Differences between EN 771– 4 and BS 6073–1
The standard contains a National Annex informing users of the differences between EN 771-4 and BS 6073-1. Some of the main issues are summarised below.
Dimensions
The specification of aircrete units by length, width and height is retained. The term ‘width’ is used as opposed to ‘thickness’. Sizes of units have not been standardised on a European level. In EN 771-4, the use of thin-layer mortar is acknowledged and tighter tolerances on permissible deviations have been introduced for the units. As a result, blocks from our ‘Plus’ and "Jumbo Plus" range are manufactured and declared to the enhanced tolerance class of ‘Thin Layer Mortar A’, which includes a tolerance on the bed height of ±2.
Density
The density obtained from the new test method is virtually identical to the old, but a new permissible deviation between measured and the declared dry density has been introduced, limiting it to ± 50 kg/m3.
Compressive Strength
The test method used to determine compressive strength is completely different in EN 771-4 compared to BS 6073-1. The preparation and conditioning produces a higher test result by some 4% as a result of testing blocks in slighter drier condition. Thus, regulatory requirements have been amended in line with the apparent increase in strength. This is the case for Approved Document A of the Building Regulations for England and Wales BS8103-2. The strength catogories in BS5628 have also changed to reflect the differences. Strengths stated by H+H UK will be the mean compressive strength of whole blocks.
Thermal Properties
EN 771-4 requires the manufacturer to provide information on thermal properties, predominantly thermal conductivity. H+H UK products will have the same excellent design thermal conductivity (lambda) values as previous, but in addition a ‘lambda dry’ value is quoted at zero moisture content to allow for comparison across the EU member states.
Durability
In EN 771-4, this is expressed as the freeze/thaw resistance. Until such time as a European test method is introduced, declaration is based on experience relevant to the intended uses of units. The British Board of Agrément has assessed Celcon blocks for use above and below ground level DPC, confirming their fitness for purpose in these locations.
Moisture movement
Drying shrinkage is a requirement given in the EN depending on the intended use of the unit. There is a different moisture content range (6 to 30% moisture content) over which movement is measured, which better reflects the actual in-use conditions. The quoted value is therefore slightly lower than the previous value, which used a much wider range of moisture test conditions.
Water Vapour Permeability
EN 771-4 requires information to be provided on this issue when relevant to the uses of the units, and in all cases when the units are used externally. The value is declared from a generic set of tables obtained from EN 1745.
Water absorption
This is required by EN 771-4 and is declared when relevant to the uses of the units, and in all cases when the units are used externally. Whilst we have quoted values available, the inclusion of the property is at the request of the French Regulators and it appears to have very little meaning in the UK.
Reaction to Fire
EN771-4 specifies that the reaction to fire classification be declared by the manufacturer when the aircrete units are intended for use in masonry walls subject to fire requirements. Independent tests on Celcon blocks have confirmed that they have the highest classification of reaction to fire. Fire resistance tables are available elsewhere (see H+H UK technical information).
Shear bond strength
This is another new characteristic, which can be declared in terms of the initial shear strength and based on fixed tabulated values or values determined from tests. This has little bearing on the design of structures in this country and H+H UK has opted for tabled values obtained from EN998-2. Thin-layer mortar attracts a significantly higher declared value.
Flexural bond strength
This has been introduced for a legal requirement for Finland only and there is no requirement to declare a value in the UK.
H+H UK Product Range
The range of Celcon products remains fundamentally the same. The Solar and Hi-Strength ranges have been specifically designed to meet the requirements for low-rise housing in the new Approved Document A of the Building Regulations . H+H UK has took the opportunity to review its Standard range in line with changes to various parts of the Building Regulations and health and safety legislation. As a result, the declared value for Standard Block strength is 3.6 N/mm² (relating to 3.5 N/mm² in British Standards), which is more than adequate for two storey houses and depending upon design, will generally be suitable for three storey construction
