Our concrete blocks are manufactured to the highest standards using quality raw materials. In order to maintain this quality, it is important that blocks are handled and stored correctly which will not only preserve product quality and appearance but will also be highly beneficial when it comes to laying of blocks and the application of finishes.
The guidelines in this section will, if adhered to, preserve product quality, maintain safety on site and result in better block laying and surfaces for accepting finishes.
Efflorescence on concrete blocks takes the form of a white crystalline deposit on the block surface and is caused by natural water-soluble salts migrating through the block and drying out on the surface. There are three things that must be in place in order to cause efflorescence:
Efflorescence can be minimized by keeping blocks as dry as possible during the build and avoid excessive wetting. Moisture ingress into the wall / cavity must be minimized by well designed and installed details such as flashings, copings, cills, the use of weepholes and so on. Excessive lime must not be used in mortar mixes and mortar joints should be tooled smooth to minimize moisture ingress into the mortar and adjacent blockwork.
This is a completely natural and harmless effect than can occasionally occur when concrete blocks are left exposed whose effects diminish over time as the soluble salts are washed away. Efflorescence is more common in the winter months. Dry surface deposits can be removed using a stiff brush (without wetting as this would re-dissolve the salts) and then any residues washed away with clean water preferably under pressure. This may have to be repeated several times allowing the blockwork to fully dry each time. The effect of efflorescence will diminish over time as the soluble salts in the blocks and the mortar are used up.
Prevention of moisture ingress into the blockwork will minimise efflorescence occurring.
General Good Practice for block laying
Blocks should be laid to achieve a good bond normally not less than one quarter of the length of the block. Other patterns may require the inclusion of bed joint reinforcement.
Protection of Finished Blockwork
Blockwork which remains unfinished and exposed must be protected from the weather with weatherproof sheeting which must be properly tied down. Care must be taken to cover all of the newly laid blockwork particularly if there is any possibility of extreme hot or cold weather.
If blocks remain wet in frosty or freezing conditions, there is the possibility of damage through repeated freeze-thaw cycling. Unused blocks stored for prolonged periods must also be protected.
We strive to ensure that our facing blocks are consistent in colour and texture from the factory that they are produced in. However, due to the use of natural locally sourced aggregates, we cannot guarantee exact matches between blocks produced at different times and appearance of the block will vary between manufacturing locations.
If using our ‘Fairtex’ or Rockfaced blocks whose finished appearance is critical, select blocks from more than one pack at a time during block laying to reduce the risk of banding or patchiness on the finished wall which may result on slight variability of shading from packs made on different days.
Vertical chasing should be restricted to ⅓ the depth of the block thickness and for horizontal chasing, ⅙ the depth of the block. Chasing is not permitted in acoustic separating party walls and always avoid ‘back to back’ chases in any type of wall.
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We are Part of the Thomas Armstrong Group
Thomas Armstrong (Concrete Blocks) Ltd
Part of the Thomas Armstrong Group
T: 01900 68211
F: 01900 602672