Laying Guides » Natural Earth Bricks

Description
The bricks are 150mm high by 90mm wide by 310 long and constructed of mixture of aggregate, sand, water and cement. Veneer weight is 170 kg/m2. The aggregate has been carefully selected to provide the earth tones and there are no coloured oxides used in the manufacture. These earth tones give the impression that the bricks are a fired clay or natural earth brick. The most important difference between a fired brick and a concrete brick to be aware of is the shrinkage characteristics which must be allowed for in a concrete brick (the characteristic of clay bricks is expansion).

NZ Standards
The construction and recommended laying method of the bricks is according to NZS 4210:2001 "Masonry Construction: Materials and Workmanship".
Design should be carried out in accordance with NZS 3604:1999 "Timber Framed Buildings" or NZS 4229:1999 "Concrete Masonry Buildings".

Base
Base shall be concrete - clean and free from laitance and loose aggregate or any other substance which would prevent bonding at the base of the wall. Apply 3 coats bituminous paint to concreete surface prior to laying 1st course of bricks. Concrete surface should be within 20mm of level. Base shall be a minimum 50mm below surface supporting the timber framing. Bricks shall not overhang foundation by more than 20mm.

Mortar
A good quality mortar mix is very important to ensure adhesion between the mortar and the bricks. materials for mortar shall be accurately measured by weight or volume and composed of portland cement, fat sand, hydrated lime and water in ratio indicated on table 2.1 of NZS 4210:2001. If required oxides to colour match the mortar to the colour of the bricks are available upon request. If bricks have been on site for sometime and/or are dry it is good practice to soak hem prior to laying to ensure the bricks do not absorb the moisture from the mortar mix and reduce its strength and adhesion.

Cavity
A minimum 40mm cavity to maximum 75mm wide cavity shall be provided. Ventilation of the cavity shall be provided at top and bottom. Weep holes at the base shall be at 900cc and 80mm high by 10mm wide. Ventilation shall be provided at the top of the wall by vertical gaps as per the base or by a continuous 10mm gap between the bricks and soffit. The cavity shall be sealed from the roof and sub floor spaces.

Brick Ties
Ties shall be fixed to timber framing or foundation walls. Fixing to timber shall be screw fixed. For single storey building (including gables) maximum tie spacing shall be 300mm vertically and 600 horizontally (alternatively 450 x 450cc). Additional ties are required within 200mm of window openings, each side of control joints and in the 1st course above windows. Specific engineering advice shall be obtained for 2 storey timber framed buildings. Ties shall be medium duty stiff ties to all seismic zones. Tie shall be embedded into middle of mortar joint with mortar above and below tie, embedment a minimum of 45mm and a minimum cover to exterior face of 25mm to the face of the bricks. Ties shall be 316 grade stainless steel in sea spray zones and elsewhere galvanized of 304 grade stainless steel.

Control Joints
Vertical control joints should be provided at maximum 6 metre spacings (measured around corners) and within 0.6 to 3 metres from corners of buildings. Joints are also required in line of window jambs to one side if window is 1.8m or less and to both sides if window is greater than 1.8 wide.

Joint shall be constructed using close cell foam rod wedged into joint 70 from face. joint is then filled with Selley's Brick & Block Masonry Silicon to within 20mm of face. A thin (10mm) mortar is placed over silicon.

To reduce the visual effect of the control joint the control joint may be stepped as per;

Openings
Galvanised steel angles ir flats shall be used to support bricks above the windows - see table 11.4 of NZS 3604:1999 or table 12.2 of NZS 4229:1999 for steel sizes. Galvanised flashings (stainless steel in sea spray zones) shall be used at head and sill of windows. Where flashings bridge the cavity provide weep holes immediately above the flashing.

Efflorescence & Sealing
Efflorescence is a natural process for cement based products and if efflorescence occurs it can be cleaned off by brush and a light wash of Spirits of Salts before sealing. Seal bricks with a "breathable" sealant such as Cemix's Cemseal (water or solvent based). Sealant shall be applied in accordance with manufacturer's instructions. Note that some sealants can be harmful to vegetation and can pit glass. Bricks should be resealed as per manufacturers instructions, typically 5 to 8 years.