- Porous ceramic blocks for construction and insulation: what’s the difference
- Foundation and waterproofing requirements
- Choice of binder solution
- Masonry technology
- Nodes of abutment of slab and Mauerlat
- Improving the energy efficiency of the building
- Finishing and insulation options
Experienced builders know that the advantages of the highest quality material can be easily spoiled by a superficial attitude to work and non-compliance with a number of installation requirements. With regard to warm ceramics, this rule is especially strict, so let’s look at the key recommendations for the construction of warm walls..
Porous ceramic blocks for construction and insulation: what’s the difference
According to their purpose, ceramic blocks are divided into load-bearing, self-supporting and non-supporting. Some manufacturers indicate the field of application of porous ceramic blocks in their catalogs explicitly – is this type of block applicable for enclosing walls, partitions, or can it be used only for insulating decoration.
It is not hard to guess that to support the floors and roofs, the wall material must have a certain compressive strength. For civil construction, the strength grade must be at least M150 for two-story buildings and at least M100 for one-story buildings. Naturally, for each building project of a house from a PCB, these requirements are individual, for example, houses with a light frame attic and prefabricated wooden floors are successfully erected from self-supporting blocks of the M70 brand, there are enough examples of this.
The real difference in the grade of the blocks is determined by the ceramic material – for stones with a high bearing capacity, clay is used as a raw material without the inclusion of burnout additives. If we bring all types of blocks to a general rough classification, then we get something like the following:
- Standard porous ceramic blocks with relatively large rectangular voids and thick partitions – ideal for load-bearing walls.
- Multi-slot blocks with a dense labyrinth of partitions are a heat-saving masonry material. They are most advisable to use in unloaded enclosing walls and partitions. Indications for the use of such stones in load-bearing walls can be established exclusively for energy-efficient houses and only after a project has been justified in accordance with the load-bearing capacity of the existing loads.
- Blocks made of porous ceramics have a real strength grade not higher than M50-M70, they are suitable only for insulating cladding and partitions with good sound insulation.
The second category of blocks is the very stumbling block. Russian builders extremely negatively perceive the idea of laying walls with more than two layers, therefore, they strive to combine both load-bearing and heat-saving characteristics in one material. It is possible to give a guarantee that a certain batch of blocks will be suitable for the perception of loads only after a trial compressive strength test in a laboratory. If the wall of blocks according to the project does not have a reliability factor of at least 1.5, the idea of a single-layer wall should be abandoned by erecting a box of high-quality blocks lined with an insulating layer.
Foundation and waterproofing requirements
When a suitable type of masonry material is determined, it should be provided with suitable conditions for installation and operation, so as not to negate the advantages of the blocks and make their inherent disadvantages less pronounced. Comprehensive recommendations on this issue are set out in the album of wall solutions from Wienerberger, prepared with the support of leading specialists from TsNIISK im. V.A.Kucherenko. We will focus on the key points, the first of which will be the foundation of the house, that is, the foundation.
Unlike solid bricks, ceramic blocks of all types have no hint of toughness or resilience. Traditional brickwork can reversibly perceive seasonal deformations due to the significant thickness of the joints and the residual plasticity of the stones themselves. For ceramic blocks, such qualities are ensured by the absence of a binder in the vertical seams, however, too large fluctuations in the foundation lead to physical destruction of blocks in the first 1-2 years of operation, and if the masonry technology is violated, even before the load from the roof and floors is taken. Hence the conclusion – the foundation for warm ceramics should be extremely even, stable and rigid. And due to the relatively high water absorption of warm ceramics, either the exclusion of water absorption from the soil is required, or the insulation of the wall masonry from the wet tape.
Depending on the type of soil, the following types of foundations are recommended:
- On normal soils – normally buried tape, for which frost heaving forces are excluded.
- For subsidence, water-saturated and sandy loam – pile-grillage.
- For unstable and highly heaving soils, hard-plastic and greasy clays – slab, including insulated.
The design of the reinforced concrete base of the house in modulus of elasticity should be carried out in such a way that the linear deformation of the horizontal plane of the foundation under the influence of all design parameters does not exceed 1/2 of the seam thickness per linear meter. Thus, for the laying of porous ceramic blocks, the average linear deformation is not more than 1–1.5 mm / m. Large-format blocks are very tolerant to the phenomena of initial and additional settlement, however, the spatial rigidity of the foundation should be selected taking into account the change in the density of the supporting soil layer. The width of the tape or grillage must fully accommodate the thickness of the walls along with the finishing layers. The release of stones over the foundation is categorically unacceptable.
Choice of binder solution
When building a foundation, it is quite difficult to level its upper horizontal plane. In some cases, this can be done after the reinforced concrete has built its design strength by grinding, however, a slightly different method is provided for porous ceramic blocks. If the total deviation of the foundation from the horizontal plane is within 10 mm, the starting row is laid on the so-called bed seam up to 15 mm thick. The mortar for the bed joint is prepared either using special “warm” mixtures from the ceramic manufacturer, or independently, with the replacement of half of the filler with perlite sand.
For horizontal joints, a cement-based mortar is used, the strength grade of which is 30-50% higher than the blocks themselves. This requirement is due to the fact that the block has an incomplete support area due to the presence of pores, which leads to the concentration of the load under the partitions of the cells. Depending on the type of blocks, the solution may have specific differences:
- For grinded blocks with calibrated geometry, liquid consistency solutions are used to ensure a minimum joint thickness (1-2 mm) and thereby reduce heat losses through cold bridges.
- For unpolished blocks, a solution is used on coarse sand of fraction 0.3–0.5 with the consistency of a thick paste to prevent the particles of the binder from falling inside the cells. Due to the uneven thickness of the blocks, the seams can reach 5-10 mm.
- To reduce the thermal conductivity of the joints, the usual mortar can be replaced with a warm mixture on perlite.
DryFix technology can be called a new word in the laying of ceramic blocks. Together with sanded large-format blocks, the manufacturer supplies special adhesive foam, the volume of which corresponds to the consumption rate and the amount of material. This technology is distinguished by an extremely high speed of erection of the building box without exposure to the curing of the binder. The least pleasant moment of technology can be called its young age: there are too few specific examples by which to judge the effectiveness.
So, when laying blocks on the foundation strip, the first stage is the application of waterproofing and a bed seam. The mixture for it has a crumbly plastic consistency, so the bed is applied entirely to each wall and leveled against the level with a curvature tolerance of no more than 1 mm / m and no more than 2 mm in general.
Ceramic stones are laid on the bed seam. They start with the corner ones, pull the mooring cord along them, then the rest of the row is taken out along it. Each stone is leveled in the transverse horizontal plane with a rack bubble level, the sediment is produced with a rubber mallet. The plane of the row is checked for every 4–5 adjacent stones by the reiki rule. When the starting row is completed, the corner stones of the second row are laid, the corners are brought out vertically, the mooring is pulled and the second row is completed in the direction from the corners to the center of the wall.
The most interesting aspects of ceramic block masonry are as follows:
- When using unpolished blocks with a thick cement mortar, each row is covered with a reinforcing mesh, excluding spillage of the binder inside the cells.
- Each new corner begins with an additional element, which ensures the binding of blocks in adjacent rows at least 1/3 of their width.
- When laying calibrated blocks, the solution can be applied in two ways:
- the stacked block is dipped into a container with a solution and the excess is allowed to drain off;
- the solution is applied to the plane of the previous row using a special roller with a dispenser.
- Interfacing with internal partitions requires cutting stones 1/3 of the depth in each even row.
- Trimming of extensions to fill the central part of the row should be carried out with the formation of the most even edge, therefore, for cutting porous ceramic blocks, it is preferable to use electric hacksaws and reciprocating saws.
- When pasting corners, stones are stacked in the opposite direction in relation to adjacent rows, forming open tongue-and-groove ends in a checkerboard pattern.
- Vertical seams of ordinary blocks are joined into a groove-comb without mortar. Ligation of vertical seams with mortar is required only where there is no double-sided tongue-and-groove connection, that is, at the junction of the pokes in the corners and when inserting extensions in the center of the row.
- In some cases, it is practiced to apply two strips of polyurethane foam to the tongue-and-groove joints..
Nodes of abutment of slab and Mauerlat
In the already mentioned album of technical solutions for walls, a typical scheme for ligating walls with ceilings is used. At the end of the wall, the finishing row is laid, represented by extras of non-standard height. In the simplest case, truncated fragments of ordinary blocks are used as extensions, but this option is applicable only for monolithic floors. For prefabricated structures, pouring of a reinforcing belt is required, in this case it is much easier to abandon additions altogether by increasing the height of the reinforced concrete crown.
The cut-in of a monolithic floor into the thickness of the wall is carried out by about a third of its thickness, that is, from 120 to 200 mm, prefabricated floors are cut into the middle of the bearing layer. Armopoyas is also not cast to the full thickness of the walls. This is due to the fact that the masonry is made in two layers in the interface unit: the outer one serves as a protection for the end of the floor, and the inner one performs a supporting function. After the installation of the ceilings, they again use the extensions laid out on the bed seam of arbitrary thickness to go into the plane of the outer row, after which the laying of the next floor continues with full-size blocks.
With Mauerlat, everything is easier and more difficult at the same time. Due to the fact that the blocks do not have a rigid connection in the vertical seams and alone remain rather fragile, it will not be a good idea to push the rafter system against them. At the same time, the cellular structure does not allow to reliably fix the Mauerlat beam. Because of this, the completion of the wall of the upper floor must be completed with 2-3 rows of solid bricks.
Improving the energy efficiency of the building
In the latter case, a pronounced cold bridge formed by the Mauerlat is striking. The porous ceramic block construction technology provides a number of versatile solutions to help reduce heat leakage in problem areas.
The first solution: lintels over openings, seismic belts and reinforced rows of masonry, ensuring the distribution of loads, are prefabricated. For example, when constructing lintel formwork, 1–2 XPS partitions are laid in it, which are fixed with steel spokes threaded through the formwork walls. When erecting a Mauerlat, insulation is inserted between the layers of masonry: for example, for the Porotherm-51 block, this sequence operates from the inside out: half a brick, then an insulation, followed by a brick on the edge, again insulation and an outer layer in half a brick. It is recommended to perform such a multi-layer masonry using flexible ties..
The second solution: use special elements as a thermal separator. Ceramic formwork trays are successfully used to fill the lintels over the openings for this purpose, they can also be used when installing the Mauerlat. Sometimes it is enough to lay out a full-bodied layer in the middle of the wall thickness, limiting it on both sides with ceramic blocks of smaller thickness. In this version of the device, it is also possible to use XPS insulating barriers..
Finishing and insulation options
Warm ceramic is a material that certainly requires the application of protective layers both from the inside and from the outside. There are several reasons for this:
- Moisture slowly evaporates from porous ceramic blocks, therefore it is necessary to protect the walls from atmospheric moisture and its subsequent freezing in the pores.
- The tongue-and-groove joints are not protected from blowing in any way, therefore, the entire building needs additional sealing.
- The inner surface of the walls is poorly suited as a base for finishing; a preparatory intermediate layer is required.
The simplest option for finishing ceramic blocks is plaster. For facade finishing, “warm” compositions with foam crumbs are ideal, for interior work – ordinary cement or lime plaster. Also, the interior decoration is quite simple to perform with sheathing or pasting of gypsum board, the thermal insulation properties of the walls will only improve from this.
Among the technical solutions from the manufacturer, there are often options with a building cladding made of porous ceramic blocks with hollow bricks. In such a finishing option, a careful calculation of the moisture accumulation of the wall should be carried out, and also flexible connections and the protrusion of the base should be foreseen in advance in the masonry.
The issue of warming ceramic blocks is one of the most controversial. On the one hand, the thermal efficiency of ceramics is much better than bricks or porous blocks. At the same time, according to the recommendations of the SNIP for the Moscow Region, the wall thickness of 51 cm is clearly not enough to reach the standard energy balance. There are two ways out of this situation: lining the house with heat-saving blocks made of porous ceramics and using a wet or ventilated facade as a thermal insulation system.
As a heater, polystyrene foam is practically not used so as not to violate the vapor permeability of the walls. The most suitable in this case are mineral wool slabs, which, when installing a ventilated facade, require a mandatory wind protection cover. For plaster facades, the paths also diverge – either high-density wool is used (120 kg / m3 and above), or a proprietary wet facade system from Ceresir (Ceresit MB), Caparol (Capatect) or Rockwool (Frontrock).