van Dyk Precast

  022 713 1937

  022 713 1928

10 Uitspan St, Vredenburg, Western Cape, RSA

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van Dyk Brickyards

  022 713 1244/5

  022 713 1500

8 Fabriek St, Vredenburg, Western Cape, RSA

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Member of the Concrete Society of Southern Africa

A good general purpose mortar is 1 cement: 1 lime: 6 sand or 1 cement: 2 lime: 9 sand. Mortar mix should not be too sloppy.

A good general mix is 1cement: 2 lime: 8 sand. Surface should be dry or nearly so before application.

Lay the blocks out without mortar to see whether the blocks fit configuration. It may be necessary to “strectch” or “shrink” a few joints to obtain a good fit.

The horizontal distance between vertical joints of adjacent courses should be at least one quarter of the length of unit used.

Lay blocks dry. Place with blind side up to provide bed for mortar. Avoid smearing mortar on block side as this shows after painting.

Joints should be pressed after mortar has partially set (1-2 hours). The half round style is probably best for appearance. Avoid raked joints as this highlights chips, etc and attracts dirt.

Avoid chopping with bolster which is untidy and generates scrap. Use a carborundum saw on well soaked blocks. Allow to dry for use or use the complimentary block on the reverse side.

Use a carborundum saw where necessary. It is best to run conduit through the wall or block cavity. Chop out individual block cavities for switch boxes, etc.

Mortar dropping should be scraped off after partial drying (approx. 24 hours). Persistent marks can be removed by rubbing with another piece of block. Use acid solutions with caution as they will etch and stain the block surface.

Normal alkali-resistant paints should be used in accordance with the manufacturers instructions. Note that mortar smears on block side and joints will show up through paint work and this should be avoided by careful laying unless the whole wall is to be bagged or plastered.

These should be spaced at approx. 5 m intervals. The wall is built is built in the normal manner excepting that on alternate courses, half length blocks are used so that a straight vertical joint is formed. The joint should then be raked out approx. 20 mm and filled with suitable mastic sealer. There is no need to build in a compressible material into the joint. Note that where the wall is to be plastered the control joint must be carried through the plaster as well. (V-joint)

It is best to protect unfinished blockwork from heavy rain by covering the top courses with plastic sheets, wood strips or even other blocks. When building recommences, use blocks of the same moisture content as those in the wall.

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