Measurement conventions

This section includes work from the damp proof course up to eaves level and includes both internal and external walls. Work is measured over all doors, windows and other openings these being adjusted at a later stage, the theory being that it is better to over measure and then make deductions and adjustment later, rather than measure net. In this way, if items are missed then at least something has been included.

NRM2 section 14 deals with the measurement of masonry and includes brick and block walling, the unit of measurement is generally the square metre.

Brickwork

The standard size for a brick is accepted to be; 215 x 102.5 x 65mm thick, however when the mortar is included this becomes 225 x 112.5 x 75mm thick. Therefore a one brick wall will be assumed to be 225mm thick and a 2 brick wall 450mm thick. Bricks are delivered to site pre-packed on wooden pallets for easy unloading and bought by the thousand, except for specially made units.

Bricks can be broadly catagorised as follows;

• Common bricks: these are suitable for general building work where the finish is not important. Common bricks are made from clay and  cheaper than the other alternatives.
• Facing bricks: facings come in wide variety of finishes, colours, strengths and prices and are used typically in the external skin of cavity walls. Also made from clay, facing bricks are weather resistant and generally finished with pointed joints.
• Engineering bricks: these bricks have low water absorption properties and a high compressive strength. Typically used in retaining walls, bridges and manholes.
• Calcium silicate bricks: sometimes referred to as sand lime facings, these are of the more easily recognisable forms facings made from sand, crushed flint and lime.

Walls of one brick thick and over can be built in common brickwork with facings on one side. In this case the facing brickwork is measured as extra over.

Previous methods of measurement classified brickwork in various types, for example; common brickwork, brick  facework and work entirely facings. There are no such classifications in NRM2 and the measurer must describe what they see. See also Sundry masonry.

Expansion joints

In order to avoid excessive cracking 16mm thick vertical expansion joints are required in brickwork, generally at 12 meter centres, whereas when using calcium silicate bricks the joints must be at 7.5 - 9.0 meter intervals and 10mm thick. The material used for expansion joints can be:

• flexible cellular polyethylene;
• cellular polyethylene; and
• foam rubber.

The joint is finished with a sealant at least 10mm deep.

Blockwork

Blockwork comes in larger units that brickwork with the standard size being 440 x 215 x 100mm, as well as a variety of thicknesses. As with brickwork, once the mortar is included this becomes; 450 x 225 x 100mm, therefore six standard bricks are equal in size to one block; an important fact, as bricks and blocks are used for inner and outer skins of hollow walls.

Dense blockwork: Dense blocks are suitable for above and below ground situations and are made from cement, sand and crushed gravel.

Lightweight blockwork: Lightweight blocks include lightweight aggregates and are generally used for the internal skins of external walls or where a high degree of thermal insulation is required. They are lighter and easier to handle on site than dense concrete blocks with poor sound insulation qualities.

Mortar

There are a variety of commonly used mortar mixes that should match the type, location and strength of the masonry. As a general rule the mortar should not be as strong as the brick or block, thereby allowing any cracking to take place in the joint and not the masonry. Therefore, a mortar mix of cement:sand (1:3) would be classed as a strong mix where as a mix of cement:lime:sand (1:1:6) would be classified as a weaker mix. Liquid plasticisers can be used in place of lime to improve a mortar's workability.

The external and internal wall contains windows and doors and the adjustment for these elements will be included in the measurement of the doors and windows.

Plan and section C-C