- What surface can the stone be glued to
- What types of stone are better
- Types of adhesives for stone cladding
- Do you need reinforcement
- Plinth finishing procedure
To veneer the lower belt of a building with stone, no special skills and equipment are required. This is one of the types of finishes that can be universally combined with most facade materials, however, for the durability of the basement, you must choose the right type of stone, adhesive mixture and preparation method.
What surface can the stone be glued to
Stone cladding is not self-supporting, but at the same time it has a significant weight: the load on the base can be 100 kg / m2 and even higher. In this case, any manifestations of deformation and cracking on the base will be reflected on the surface of the base. As a mute truth, you need to accept the following: the surface for finishing with a stone must be even, solid and monolithic.
The easiest way to finish with natural stone is a reinforced concrete foundation without insulation. If, when pouring concrete, the formwork was covered with waterproofing, the surface adhesion will be almost zero, it is necessary to remove the top layer with a disk disc and cover the base with concrete-contact soil. Leveling plaster should only be applied if the foundation has significant curvature, for example from formwork divergence. Irregularities up to 5 mm / m may well be leveled with a layer of glue, besides, the unevenness of the face of the stone helps to visually smooth out the imperfections of the base.
The need to reinforce the base for finishing with a stone is unconditional. If such a plinth lining was provided for by the project, the outer wall of the plinth tape is reinforced with a mesh with a cell of about 150 mm. If reinforcement has not been performed, the formation of cracks can be excluded only by preparatory plastering of the basement with a layer of 15 mm or more on a steel or plastic mesh.
It is also possible to decorate a warmed base with natural stone. In this case, the thermal protection belt is made of extruded polystyrene, which acts as a deformation damper, therefore, there are no requirements for the solidity of the base. In particular, it is possible that there may be brickwork under the insulation or interfacing of the grillage with the wall box. However, the final preparation of the insulation surface becomes even more complicated, for the best result it is necessary:
- Remove the extrusion film from the insulation using an abrasive mesh.
- Wipe the surface with a plaster mixture on a polymer binder.
- Roll out a fiberglass facade mesh with a density of 150 g / m2 over the still fresh plaster2 and cover it with another layer of plaster.
- After hardening, strengthen the plane with special disc dowels with spacers (DS-2, 1MN) through the insulation into the bearing layer.
- Carry out the leveling of the plane with polymer facade plaster (layer 2.5–3 mm).
- Immerse the Stren C1-5 mesh in fresh plaster and complete the leveling by building up the overall “crust” layer over the insulation to 8-10 mm.
- After drying, the base must be treated with deep penetration soil for dust-free surfaces, after a day you can invite a bricklayer.
What types of stone are better
The whole variety of natural stone can be divided into two main types – facade tiles and non-format natural stone. The approach to the organization of work in both cases is different, although both materials have the same requirements for the preparation of the base.
You can cover the basement with facade tiles yourself. A clear ordering, a simple layout scheme, a calibrated element thickness and the use of embroidery inserts – all this greatly facilitates the work. From the tool you only need an angle grinder with a cutting wheel for a stone, a rack level and a spatula with a comb.
It is better to entrust work with non-formatted stone to a bricklayer who has practical experience in carrying out such a decoration. In addition to the fact that stones are of different sizes and they have to be sorted and adjusted to avoid unnecessarily thick seams, some elements require preparation of the seamy surface. If the back side of stone tiles is factory-processed and has excellent adhesion, then natural stone may have irregularities, delamination and efflorescence, which impairs adhesion to the base layer..
Appearance aside, different rocks show differences in usability. Sandstone, limestone and shell rock are quite loose and porous, therefore they retain moisture well. Because of this, there is a great risk that the base will eventually become covered with a green coating, that is, subsequent treatment with a water repellent is required.
Denser mineral rocks such as granite, dolomite and marble are highly dense and hardly absorb water. The cladding of them is characterized by very high frost resistance and resistance to weathering. In turn, the absence of large pores negatively affects adhesion, therefore laying on a conventional cement mortar is impossible..
We should also mention artificial stone – products made of sand concrete, imitating a wide range of natural rocks in color and texture. The main disadvantage of such a stone is its poor resistance to wetting and, as a result, a high risk of destruction during defrosting. Such a stone is not recommended for facade decoration, it is more suitable for interior work.
Types of adhesives for stone cladding
Facing with natural stone should be carried out using the highest possible quality adhesive mixture. It does not have to be prepared with a polymer binder: a high-quality cement slurry is also quite suitable, but only for rocks of sedimentary origin with good absorbency and large pores.
In addition, there are a number of additional features when choosing an adhesive:
- It is much better if a ready-made dry mix with an optimal ratio of ingredients and all the necessary modifiers is purchased for facing the basement. The lower belt of the building is most susceptible to operational loads, at the same time, the loss of even one element will hopelessly spoil the appearance.
- The adhesive mixture used to fill the joints must be tinted without fail. Facing with natural stone is not performed without joining, however, the seams can either smooth out the transitions between the elements, giving visual solidity, or vice versa – emphasize the masonry with contrasting veins.
- The glue mixture should not include gypsum and other substances that can shrink during changes in humidity.
- The cost and, accordingly, the quality of the adhesive, as well as its ultimate pull-off force, should be the higher, the greater the specific gravity of the facing. Also, keep in mind that the strength of fixation is always inversely proportional to the thickness of the glue line, so the potential of high-strength glue will only be revealed if the back surface of the stones is well aligned..
- The glue for working with non-formatted stones should have a significant pot life (about 1-1.5 hours), while for stone tiles the optimal setting time is 30-40 minutes.
Do you need reinforcement
When using format stone for facing, it is possible to ensure a minimum thickness of the joints, due to which the finishing layer acquires a high uniformity. In this case, there is no need to lay the reinforcing mesh directly under the stone..
The situation is somewhat different if the stones do not have a sufficiently tight fit to each other. Due to the significant thickness of the glue joint, shrinkage from changes in temperature and humidity can lead to cracks along the perimeter of stones or crumbling of the mortar filling the joints.
However, it should be remembered that the adhesive layer under the stone is highly susceptible to getting wet and gas exchange is present there. For this reason, the only possible options for the reinforcing mesh are fiberglass or galvanized. The size of the cell should be about a third of the size of the stone, the diameter of the wire should be no more than 1/5 of the thickness of the glue line.
The cladding mesh has no mechanical attachment to the base. It is simply embedded in a layer of fresh glue, which remains after wiping off a section of the wall just before gluing the stones. It is also not necessary to use a mesh on the entire base, you can strengthen only the most problematic areas prone to getting wet, increased heating in the sun or the formation of ice.
Plinth finishing procedure
Recall that it is possible to start facing with a stone only when the surface of the basement is well prepared and leveled. The order in which the stone is laid differs depending on the format. For example, working with stone tiles follows the following algorithm:
- The first bottom row is laid out entirely at once along the mooring cord or, if possible, along the pre-bolted starting profile UD-28.
- The degree of indentation of the tile is normalized by the upper edge and the flat back edge.
- When the first row is kept according to the setting time of the glue (about an hour), the lining is continued. The second row begins with a scoring pad, which provides an offset of one third of the tile length.
- On a plot with an area of 0.5-0.7 m2 a wiping layer of glue is applied under a 6–8 mm comb, strips are oriented vertically.
- On the reverse side of the tiles, before laying, the adhesive is applied in the opposite direction with a comb of the same size.
- When using jointing strips, they are pressed into the wiping layer flush with the back surface of the tile, while the vertical direction of the strips does not allow excess to be squeezed out.
- Vertical seams in the same row are formed using short lengths of a jointing bar, which are then removed.
- After finishing the cladding, the seams between the tiles are filled with glue from a plastic bag with a cut corner and sewn with a knife of the appropriate width with a semicircular profile. Only the seams, in which the jointing strips are inserted, remain without joining, in which case the vertical seams are sewn by pressing the knife first to the upper rail, then to the lower one, so that the joining profile converges in the middle with a small bulge.
But when working with a non-formatted stone, the procedure is somewhat different:
- The bottom row is always laid on the starting bar, usually large stones are used at the beginning of the laying, cut in half.
- A fairly extensive section of the wall is wiped at one time – about 1.5-2 m2. In this case, due to the unevenness of the seamy side, a large comb depth is required – up to 15 mm.
- The stones are pressed into the glue and compacted towards the previous ones using a rubber mallet.
- The protruding glue residues are removed immediately with a wooden chip, the front surface of the stone is wiped clean with a wet brush.
- After the cladding is completed, the cleared seams are filled in by analogy with stone tiles. It is recommended to use a flat knife or a jointing wedge, depending on the preferred appearance.
- After the lining has dried, it is washed again until efflorescence disappears, dried and opened with a water repellent, if necessary.