- What are decorative blocks?
- Fence carrier system
- Start row device
- Rules for laying decorative blocks
When looking for an inexpensive and easy way to create a stone hedge, look for hollow decorative blocks. In this article, the RMNT website will tell you about the features of working with this material and methods of erecting decorative masonry, which do not require the skills of a professional bricklayer.
What are decorative blocks?
There are now a lot of large-format materials for masonry, but only a few of them are suitable for the construction of structures that are operated without any protection from the weather. After all, a stone fence, despite its apparent simplicity, is subject to serious stress during temperature drops due to freezing of moisture in the pores of the material and frost heaving of the soil.
The decorative block, sometimes called the Besser block, is a parallelepiped-shaped product made of concrete or fired clay. As a rule, the format corresponds to the general construction format: 200x200x400 mm with a minus tolerance of 10 mm. The block is hollow in structure, the void index can vary from 35 to 50%. Due to this, the weight of the product is reduced and, as a result, its cost. At the same time, for a fence that does not carry any additional loads, the use of hollow masonry is quite justified.
A characteristic feature of the blocks is their decorative properties. Depending on the material used, the method of manufacturing and surface treatment, the block can have a chipped, smooth, stony, embossed, fine-grained surface and be painted in any color due to either the use of a filler of the desired shade, or the introduction of a pigment dye into the raw material.
In terms of compressive strength, the blocks correspond to materials of grades M50 … M100, and if the voids are filled with concrete, they are almost identical to monolithic products. Frost resistance is about F250, which corresponds to a service life of 20-30 years, although outside harsh climatic conditions such masonry will last much longer. There are several varieties of Besser blocks, because they are used not only for the construction of fences, so finding material with the necessary characteristics is not a big problem.
Fence carrier system
The decorative blocks themselves are quite strong, but the durability of the fence is determined by the general characteristics of the masonry, which must correspond to the bearing capacity of the base..
A full-fledged foundation with normal depth is almost never poured under a Besser fence, being content with an ordinary concrete tape. Its width is about 30 mm, which is sufficient for fences up to 2.5 m high on normal soils. The depth of occurrence is determined by the location of a layer of rather dense sedimentary rocks – as a rule, 30–60 cm. Reinforcement is performed with four strings of profile reinforcement with a diameter of 12 mm, and when lying below the CNV – 14 mm. The reinforcement cage is positioned with a protective layer of concrete of at least 80 mm.
The use of tape as a foundation is justified by the high deformability of the hollow masonry, however, when the cavities are filled with concrete, the stiffness and weight increase, which forces the foundation to be strengthened and the depth of laying.
It is better if the Besser fence is broken by pillars into sections of 3-5 meters. To do this, the foundation is cast not with an even tape, but with pouring pedestals of such a size that the base protrudes 50–80 mm beyond the masonry. It is possible to cast the entire tape of this width, but it is less aesthetically pleasing and not economically justified. When erecting pillars, it is imperative to leave mortgages protruding from the foundation at least 70% of the pillar height. As these, a channel, a pipe, or a square frame made of 10 mm reinforcement will fit.
Start row device
Work on the construction of the fence can begin on the 7-10th day of concrete setting. First, a starting row is laid out, which completely sets the configuration of the masonry and serves as a basis for alignment.
First of all, waterproofing is installed, designed to protect the masonry from moisture migration from the concrete. Roll waterproofing for foundations is best suited for these purposes: with a sufficiently dense layer of mastic, it has a reinforcing base and, due to this, is most durable. A cut-off layer can also be arranged from cheap and improvised materials: one layer of roofing material, two layers of polyethylene film for greenhouses and another layer of roofing material.
A layer of thick cement mortar up to 30 mm thick is laid on top of the waterproofing. It is necessary to level the unevenness of the concrete tape and provide a perfectly flat surface of the first row. The easiest way is to remove the masonry along the lacing, first setting the corner stones. If the span of the cord exceeds 10 meters, it is better to install intermediate stones. The task of the key blocks is to serve as markers for deriving the general horizontal level and face plane. If, as the first row is completed, it becomes necessary to move the stones, they can be torn off and placed again on a fresh solution..
However, the position of the first stones along which the cord is pulled is easier to calculate in advance, given the thickness of the seam. It is 8-10 mm for standard blocks and can be up to 12 for large-format ones. It is also not forbidden to completely lay out the starting row on a dry one, and then transfer it to a solution – so the alignment will be of better quality. In any case, the front plane of the masonry is aligned with the stretched cord, and the horizontal one – with the slatted level and the rule.
It is important to remember that the layout of the starting row also specifies the configuration and the sequential layout of the pillars. In the simplest case, you can use conventional in-line blocks laid out in a hollow tower. But in this case, the pillars will protrude 20 cm above the plane of the fence, which looks appropriate only on large fences. To make the protrusions more concise, you can use special corner facing blocks, due to which the protrusion of the pillars can be reduced to 6-10 cm.
Rules for laying decorative blocks
When the starting row hardens for 20-30 hours, laying can be continued on the formed flat surface. It is not necessary to wait for the full hardening period in cases where the dimensions of the fence allow laying only 2-3 rows per day, but if the lower row is overloaded until full set, high-quality alignment will become impossible.
Textured and chipped blocks do not form strict seams, due to which visually the masonry does not express minor flaws. At the same time, if the surface is smooth or polished, any jointing defects will be present. Therefore, it is better to lay the masonry according to seam patterns – square bars of the required thickness, which are removed from the seams after aligning the next block. With 2-3 sets of such pads, you can confidently and quickly erect masonry, leaving enough time for the bonding material to set.
Since the masonry of decorative blocks is front, it is not recommended to use ordinary self-prepared cement mortar for dressing. It is better to heed the manufacturer’s recommendations: the use of special mixtures or additives will ensure full chemical compatibility and eliminate the formation of efflorescence.
To prevent the vibrations of the base from being reflected in the masonry in the form of cracks, reinforcement should be performed. The first type is laying along the seam of a steel or polymer mesh, which helps to prevent laminar shifts. It is also necessary to tie up the pillars and the spans between them using 8 mm pieces of reinforcement 60-80 cm long.
An important rule of thumb is to fill and grout joints 2-3 days after the blocks have been laid. Using a construction syringe or a dense plastic bag according to the principle of a pastry sleeve, the seams are filled with a mixture whose water absorption is no less than that of the blocks themselves. Such a strict necessity is associated with high voidness: the flow of water through a thin layer of solution remaining after removing the square rod is almost inevitable. This can lead to waterlogging of the masonry and a decrease in its frost resistance..