The durability of the
façade as well as internal plaster depends mainly on the type of plaster, their
construction and the substrate.Currently, a wide range of plasters is available
on the market, based on various binders. This
material is devoted to the simplest and most often used cement-lime plaster,
which despite its simplicity, can create a lot of problems. Especially used on new masonry
materials that are much weaker than old (bricks) or smooth, like glass
(concretes), characterized by low adhesion. In
the case of ceilings, especially concrete ones - with low adhesion, one must
also remember the force of gravity. Applying
plaster with a greater thickness, for example to cover the cables, causes an
increase in weight to about 10
kg per 1
cm of thickness.With low adhesion
to the substrate, too much plaster weight leads to the plaster falling off. Most often, the first opinion that
appears on the site is that the fault lies on the side of the material. Often, however, the same material,
from the same lot, on the walls does not show any disturbing symptoms.
The durability of the
façade as well as internal plasters depends mainly on the type of plaster and
the substrate. Currently, a wide
range of plasters based on various binders is available on the market.
This material is devoted
to the simplest and most commonly used cement and lime plasters, which despite
their simplicity can create a lot of problems. Especially used on new masonry
materials that are much weaker than old (bricks) or smooth as glass (concretes)
characterized by low adhesion. In
the case of ceilings, especially concrete ones with low adhesion, one should
also remember the force of gravity. Applying
the plaster to larger thicknesses, for example to cover the cables, causes an
increase in weight of about 10 kg per 1
cm of thickness. With low adhesion to the substrate,
too much plaster weight leads to the plaster falling off. Most often the first opinion that
appears on the construction site is that the fault lies on the side of the
material. Often, however, the
same material from the same batch on the walls does not show any disturbing
symptoms.
Thick, too-thick cement
plaster on the ground for gypsum plasters
Macroscopic picture of
strong plaster on a weak unbearable surface
Applying thick new
plaster on old painted plaster
Cheaper traditional
plaster without hudrophobic additives at a small thickness, soaked, frozen and
busted.
Plaster on the facade
applied to the gypsum cardboard board
For proper use and
long-term durability, pre-made plastering materials should be prepared with appropriate
portions of water.The material quality is guaranteed by the manufacturer. In the case of plasters performed on a
construction site, the quality and durability depend on so many factors that
the contractor bears full responsibility. due
to the high risk of not getting the quality of the finished product, this type
of mixture is increasingly being abandoned.
Considering the
proportions of cement, lime-cement plasters should also be distinguished. The ratio of lime to cement has a
decisive influence on the properties of the plaster, especially its strength. It should be remembered that walls
made of weak (high porosity of "warm" building materials) or damaged
by the passage of time (monuments) of masonry materials should be covered with
weaker plasters. Strong plasters
require a strong substrate, otherwise they will crack and become
detached.Often, however, these basic building rules are forgotten. You can meet with the conviction that
a weak wall, which is also falling apart, should be "reinforced" with
plaster with more cement. It
should be remembered that plasters do not have structural properties. Their basic role is to level the
surface, protect against weather conditions and give the plaster surface the
required appearance. Plasters may
be typically undercoat, leveling surfaces on which other layers (plaster,
glaze) etc., or typically decorative, will be made, giving the required form of
finish. Without a good
preparation of the substrate with a primer plaster, it is difficult to properly
make a more expensive plaster or decorative putty.
All plasters can be
divided into two groups. Prepared
on the construction consisting of the basic ingredients: sand, cement, lime and
water, and those factory-ready in bags, which require only adding water. While the factory-ready (with the
right proportion of water) have a specific application and predictable
parameters on the construction site are difficult to predict when it comes to
parameters. Their properties over
time depend on many factors. Although
they are usually cheaper, it is difficult to determine their properties and
durability on new masonry materials. They
are not suitable for machining, which is the standard with current short
delivery times. They also do not
have hydrophobic agents that protect the factory external plasters.
It should be remembered
that the old plasters were much thicker, forced by thicker grain and unevenness
of the walls. It is their
considerable thickness that protects against soaking. Currently, with almost ideal and even
walls, which do not need to be evened up, the thickness of plasters often
decreases to a few or a dozen or so millimeters. They are often covered only with
putties or adhesives for polystyrene with embedded mesh. While in the rooms it is often enough
to put the filler on the outside, where we deal with the impact of harmful
atmospheric factors, the thickness of the plaster determines its durability. Temperature differences in summer and
winter, especially rainfall and snow, causing cyclical moisture, require
plaster with higher strength parameters. Thicknesses
for external plaster should start from 15mm. Thinner
layers do not withstand temperature stresses, damp in all their small thickness
freeze during the winter and fall off the ground.
Many later problems
appearing on the façades or in the interiors result from poorly chosen,
improperly treated surfaces or on improperly prepared plasters. Unfortunately, these facts are not
always associated with each other. Any
changes to external layers of plaster require verification of the correctness
of individual stages. The correct
execution of the plaster affects the durability of the subsequent finishing
layer. Guided by the principle
that what underneath and can not see it can be cheaper and worse can cost a
lot. The best examples are
elevations made of the cheapest
materials but finished with brand-name good plasters or paints, which over time
become discolored or peeled. At
first look for guilt in decorative plaster or paint, omitting the matter of the
substrate. The durability of the
final layers always depends on the durability and adhesion of the substrate. This also applies to thermal
insulation systems, which are already applied obligatory during the
construction of new buildings.However, the most failures with the system
falling out, it happens mainly on the old elevations subjected to
thermo-modernization. Often, old
plasters do not stick to the walls, the use of pegs and plots in this case does
not help much. It is the poorly
prepared, unbearable substrate that is the main cause of most failures.
Only complete insulation
systems with one manufacturer guarantee quality and durability.
Self-respecting
manufacturers of construction chemicals offer systems that increase adhesion to
the substrate for their plasters in the form of primers, coatings and even
contact putty for concrete. As in
the case of thermal insulation systems where individual materials are matched.
Apparent savings through
the purchase of individual plaster or adhesive materials from different
manufacturers, suggesting only the price almost always leads to problems. Manufacturers' data systems are
designed as a whole and mixing
them together can lower the system's durability as a whole. If it comes to complaints, they may
not be recognized. Manufacturers
have a basis for this, because they are responsible for the quality of the
system, as a set of self-tested products manufactured by them. They do not assume responsibility for
the systems of layers of products from different manufacturers, and therefore
not tested with each other.
