Delivery and storage The bricks delivered to the construction site should be stored on a level, stable and uncontaminated surface. When the modular blocks are delivered without packaging, a ventilated cover should be placed over the bag in unfavourable weather conditions.
Silka thin-bed mortar This is available in summer and winter qualities. The Silkafix must be mixed with tap water in accordance with the instructions on the packaging.
Kicker course mortar Mix the mortar for the kicker courses in the ratio 1c : 3s. Do not use wet prefab mortar (this produces poor curing in wet weather and thick joints).
Auxiliary tools Special Silka mortar applicators, mortar scoops and clamping devices have been developed for laying modular blocks.
Construction Silka modular blocks can be stacked both manually and using the crane depending on the weight and the circumstances. Blocks that are supplied on pallets can be easily transported using a pallet-truck. It is common for blocks to be stacked using a forklift, digger or hand pallet truck. Because of rising damp, the stacked calcium silicate masonry unit blocks should be laid on wooden laths if they are not on pallets. They must be stored on the job in such a way that rising damp and/or contamination from water splashing up is avoided. Silka modular blocks must be laid on a clean, level surface. As these are generally absent in building practice, a kicker course of mortar or Silka kicker course or standard blocks will have to be laid prior to construction. This kicker course has a two-fold function:
create a level surface
accommodate any difference in height between the standard blocks and large format blocks and the free floor level
The kicker course will have to be level in both the transverse and longitudinal planes. Positioning against a line will ensure the correct positioning in the longitudinal plane. The transverse plane can be checked using a kicker course spirit level. Manual laying of Silka modular blocks is normally carried out by a single person. A team of two people is needed to mechanically lay the blocks. The thin-bed mortar is laid in the bed joints using a mortar applicator. A mortar scoop is used for the vertical joints. After mortar has been applied to the wall, the excess thin-bed mortar remnants have to be removed. If the wall has a cavity side, then the remnants must be removed here too, so that the insulation plates have a good connection to the wall. Working manually will be most economical in situations where short walls are required or with walls that have many breaks due to recesses making few multiple positioning actions possible. And in circumstances where there is insufficient space for the crane, it will also be more efficient to work manually. In all other circumstances work can, in principle be done mechanically. The best working method should be decided on a project by project basis.
Silka modular blocks are laid with shoved joints using a thin-bed mortar whereby a bed joint thickness of 2 mm and a vertical joint thickness of 3 mm should be used. It is recommended that the modular blocks are laid in stretcher bond. Silka modular blocks that are heavier than 14 kg can only be laid mechanically. Fitting pieces can be made in-situ in two ways:
cutting: a cutting machine with top and bottom blades suitable for calcium silicate should be used for this
sawing: using a diamond saw, using an angle grinding disc
If wall, supporting or adjusting structures do not provide adequate shoring, the walls should be provided with a sound shoring structure as soon as possible after completion. The correct amount of shoring depends on the thickness of the wall and the number of transverse walls constructed at the same time. It is recommended that the Health and Safety Executive guidelines are followed. As a rule, a wall must be supported every 5 metres by transverse walls or by shoring.
Practical tips for building using Silka modular blocks
Protect the calcium silicate masonry units from becoming too wet.
Only use the supplied Silkafix thin-bed mortar.
Mix the Silkafix thin-bed mortar in accordance with the instructions on the packaging.
Do not apply the thin-bed mortar for the bed joint with a trowel or mortar scoop, use the mortar applicator. Use the mortar scoop to apply the thin-bed mortar to the vertical joint.
Moisten dry calcium silicate before constructing walls, by using a wet hand brush to wet the joint sides before applying the mortar.
When laying mechanically follow the safety instructions for the crane.
Never pour concrete directly onto calcium silicate, lay foil over the brick first.
Remove thin-bed mortar remnants within four hours
Never stick tiles onto a plaster layer.
Include sufficient movement joints (Xella will provide you with advice in this regard).
On cellar walls apply a good layer of kicker course mortar and mix a water-sealant with the mortar.
When laying the kicker course, the sledge hammer should be used as little as possible; do not tap the kicker course blocks into the mortar but nestle them in.
Silka CS elements and Chamfered elements
The large format calcium silicate blocks can be laid mechanically by a team of two people. One person is needed to operate the crane, pick up the previously stacked blocks and transport them to the wall under construction. The second person sees to the application of the thin-bed mortar for the bed joints and vertical joints and ensures that the blocks are correctly positioned. The bed joints must be laid using the thin-bed mortar applicator, the slide of this applicator must be set to such a size that a permanent joint thickness of 2 mm remains. The thin-bed mortar for the vertical joints is applied from the bottom to the top of the previously positioned blocks using the thin-bed mortar scoop. For blocks with a thickness of 300 mm, it is recommended that the mortar for the vertical joints is applied by the person operating the crane, before he transports the block to the wall. Applying the mortar with a trowel is not recommended. If necessary, the placement of the blocks can be tightened up using a heavy rubber hammer to close the vertical joint. Excess mortar should be removed with a spack knife after it has hardened a little.
Scaffolding and shoring
The large format block walls can be immediately erected to full storey height. It may be necessary to shore the walls depending on the weather conditions and the thickness of the walls. In doing so, the Heath and Safety Executive regulations (“Arbeidsinspectie”) should be adhered to, including in relation to scaffolding. During and after construction the walls should be prevented from falling over. Walls falling over or sliding off the kicker course can be caused by wind load (pressure + suction) or because of an impact load that could occur during assembly of the floor slabs for example.
Hoisting and dowel holes
At the top of every block there are 2 holes, 500 mm centre to centre, for mechanical laying and for dowel placement. Dowels are used with the large format block system to simplify the accurate positioning of the blocks and to prevent them from 'floating'. The dowels are made from recyclable plastic (polypropylene); the blue colour is obtained by adding a cadmium-free colouring agent. A maximum of 1.85 dowels are needed per m2 (1 per whole large format block).
Storage Place the pallets on a level, stable and uncontaminated surface.
Preparation Pre-processing check (by the client) of the working wall drawings supplied by the factory. Large format blocks, fitting pieces and kicker course blocks that are too dry should be moistened one day before use.
Construction The large format blocks are laid mechanically according to the working wall drawings with calcium silicate thin-bed mortar, bed joint thickness 2 mm, vertical joint thickness 3 mm. The vertical and bed joints must be laid as shoved joints. The chamfered large format blocks are laid without thin-bed mortar in the vertical joints. If however the performance requirements set in relation to soundproofing exceed the properties of a wall constructed without mortar in the vertical joints, the vertical v-joints should be sealed to at least 3 mm on one side, or the chamfered large format blocks should be laid using mortar in the vertical joints.
Auxiliary tools Special Silka mortar applicators, mortar scoops, clamping devices and cranes have been developed for laying large format blocks.
Finishing Silka CS elements can be used for backing brickwork and can be finished with skim plaster ready for wallpapering. Silka CS chamfered element can be used as double-sided fair-face masonry and do not need finishing. In order to avoid contamination of the wall from the environment, it is advisable to treat the wall with a dirt-repellent product, Muurcape for example, or an equivalent product.
