Sealing cracks in plaster: how to do it right
To understand what and how to close a crack in the plaster, you need to find out the nature of its appearance and determine the base material on which it arose. Because of this, as well as of the location of the defect (inside or outside the building), the type of “patch” and the technology of the work depend.
The content of the article
Why do cracks appear on the walls?
The reasons why plaster is cracking can be very different.
The most common are:
- Building shrinkage;
- Sudden changes in humidity and air temperature;
- Violation of technology when laying brick;
- Violation of the technology of applying plaster;
- Incompatibility of wall material and leveling mortar;
- Improperly prepared solution;
- Too much layer thickness is the clear reason why fresh plaster cracks;
- Non-compliance with the conditions under which it must dry, etc.
And in the case when cracks appear on the plastered plasterboard surface, the reason may be that the installation instructions for the frame and the sheets themselves were not followed, as well as the technology of sealing joints between them.
Ways to eliminate defects on different surfaces
Regardless of the cause of the crack on the plaster, masonry, concrete wall, it is necessary to close before proceeding with further finishing. And the point is not that decorative materials will not be able to completely hide defects that spoil the appearance of the walls, although this is also an important aspect.
If this is not done, the material will begin to break down further, since moisture will penetrate through the cracks. Timely repair is especially necessary for external walls subject to aggressive environmental influences and high mechanical stresses.
Plaster repair
AT cement-sand plasterhaving low elasticity, cracks after drying always appear with rare exceptions. Sometimes this happens even earlier, during the hardening process. If you want to know why the fresh stucco is cracking, there can be several reasons: it is either too thick a layer applied in one pass, or drying with strong heat and dry air without wetting, or a high sand content in the solution.
In any case, the cement plaster is primed and putty, but sometimes small cracks appear on it, and even on the wallpaper. To avoid this, the walls before the putty are reinforced with a spider line (painting glass fiber) or a fiberglass mesh.
For reference. Glass reinforcement is also suitable for reinforcement, but their price is much higher than the listed materials, therefore their use is justified only if they are the finishing decorative layer intended for painting.
Fiberglass is glued (seeFiberglass for putty - purpose and installation rules) on special glue after applying and drying the primer. Then the surface is putty.
There are other ways to repair small cracks in the plaster.
- If they are small, like a cobweb, formed as a result of shrinkage of the solution, the surface is treated with deep penetration impregnation, which strengthens the surface and prevents cracks from growing. After drying, the impregnations are covered with a thick dispersion paint;
- Highly visible cracks can be repaired with a mixture of cement with PCI emulsion or with PVA glue.It is applied with a brush.
In the case of new buildings or buildings built on unstable soils, the reason why cement plaster is cracking is their uneven shrinkage or the occurrence of internal stresses in the structures. In this case, cracks can be very large and deep, even through, especially at the joints of structures of different materials. Their termination is carried out according to the following technology:
- Cracks are broken, i.e. with the help of milk and chisels expand by knocking the edges at an angle of 45 degrees. At the same time, weak adjacent areas of the plaster are removed;
- Then they are cleaned of residual dirt and dust by sweeping with a hard brush. You can also use a vacuum cleaner;
- A repair mortar is being prepared in which you can add fine gravel or pieces of broken brick if the crack is very large and deep;
Note. The type of repair mortar depends on the place of work. If cracks in the outer wall are closed, it must be weatherproof and prepared on a cement-lime basis.
- Before closing the crack, moisten it with water from the spray gun or with a wet sponge or brush;
- The solution is applied with a spatula to the defect and pressed inward so that it fills all the voids. Surplus immediately removed flush with the wall;
- When it dries, the repaired section of the wall is sanded and plastered.
If the crack in the wall is cross-cutting and wide, you will have to do it yourself on one side of the formwork, which prevents the flow of the solution. This can be a board or plywood shield, the dimensions of which allow you to capture the entire damaged area. It is screwed to the wall with screws or held by struts and remains in place until the solution in the crack solidifies.
Brick repair
One of the reasons why the stucco cracked on a brick wall may be a failure to comply with the masonry technology. A crack occurs in it and tears the plaster itself.
In this case, it expands and deepens in all directions with the capture of masonry, and the plaster around is removed to firmly held areas.
Further, two repair options are possible:
- Cement mortar, similar to the one on which the brick was laid, or a similar material - cement plaster, tile adhesive, etc. The technology is the same as described in the previous chapter;
- Sealantwith which a crack in a brick is filled with a construction gun. It should be filled to the level of the masonry plane, and the excess immediately removed with a rubber spatula or finger soaked in a solution of any detergent. After the sealant has dried, the wall section cleared of the plaster is plastered again.
It is important. Silicone sealants cannot be used to seal cracks, since plaster and putty mixtures do not stick to them, paint does not hold.
The second option is much more expensive, but also much more reliable: after drying, the sealant becomes elastic, easily tapers and expands, preventing cracks from forming again. In this way, deep cracks in the plaster can also be closed.
Repair of drywall constructions
Quite often from people who have just completed drywall repairs (seeGypsum plasterboard technology: installation methods), you can hear the question: what to do - the plaster is cracking and the wallpaper is torn on the walls leveled by it?
The algorithm of actions depends on what led to the following consequences:
- If this is an incorrectly mounted or poorly fastened to the base frame, which staggers, not allowing the sheets to maintain a stable position, then closing cracks is useless, they will appear again. There is only one way out - to redo everything.
- If defects have arisen due to deformation of drywall sheets as a result of a flood or exposure to high humidity, there is nothing left to do but change the lining.
- If the technology of sealing joints between sheets was violated, then the problem is solved quite simply. Seams are cleaned of old putty and repaired again according to all the rules with the use of reinforcing tape.
- You can use a more reliable method with reinforcing the entire surface of the fiberglass. After gluing it, the walls are completely putty and sanded. The technology of this process has been repeatedly described on this site.
Conclusion
Cracks on a newly repaired or old and seemingly reliable and durable wall are a big nuisance. But anyone can cope with it. Material and labor costs, of course, are inevitable, but there is nowhere to go.
If you decide to repair the surface on your own, it will not hurt you to watch a useful video in this article to better understand the technology.
