How often do we come across the problem of breakage of stone tiles a few months after installation ? What a disagreeable moment it is when the worried owner calls up commenting that the stone floors installed only recently is showing cracks or that the polish is gone, and that he wants a solution immediately ! And no,  the stone did not break because a heavily loaded truck drove over the 2 and 3 cm stone tile flooring.

Problems come up frequently because at the time the stone was installed, no one paid any importance to the moisture level in the concrete substrate. In this interview, Mr Walter Denzel, of the company DNZ-DENZEL (info@dns-denzel.de) a recognised expert on this problem, answers why this problem exists and how to solve it.

QUESTION-What is the risk that stone installers take by ignoring the importance of moisture content in concrete mixture?

ANSWER- All kinds of unexpected and serious problems come up when the moisture content is ignored.

QUESTION- What are these unexpected and serious problems and when do they become visible ?

ANSWER- The stone “glue” (when used) sometimes becomes soft and loses adherence.

Stone surfaces become rough and dirty and cannot be cleaned. Stone surface changes in colour. Cracks in the stone cannot be closed. Hydrophobic liquids do not penetrate deep enough, and are thus not effective. Also rusty stains form on the stone. And the list does not stop here. Cracks can occur in the basement material once the substrate dries ( and shrinks).

Since moisture and bacteria need calcium ( found in concrete) and normal temperatures are needed so as to get the best growing substrate, different kinds of “sickness” may result when there is too high a level of moisture content in substrates. Moisture related problems in the case of wood can become visible only a few hours after installation. Most problems in stone installation become visible only after a few months or a year. Moreover, and this has happened quite often, even in new constructions, where poor quality concrete has been used, problems with stone have occurred even before the official opening ceremony !

QUESTION-  What can be done to prevent such problems from occurring ?

ANSWER-  Everybody who manufactures concrete and concrete mixtures must inform others who will be using them of the water-equilibrium-value of that particular concrete-mixture. Only when we know the equilibrium-value that is not dangerous can we then decide what moisture content level can be dangerous and what level is not dangerous. (Water equilibrium= concrete water dump pressure value MINUS air water dump pressure value).

Water-Dump-Pressure out of the construction-Material   /  Air-Humidity-Pressure  = Equilibrium

Example- If we are informed that a concrete mass can lose moisture down to 2 %, we can then decide that whether 2.5% ( 500 gms “free dangerous” water per 1 m2 / 5 cm concrete) measuring value is dangerous for our installation material or not. But if we do not know this, we cannot evaluate what is the “dangerous” level, because every concrete-base material can have a different equilibrium value.

QUESTION- What is the reason for too much moisture ?

ANSWER- The main reason is incorrect concrete mixture and bad cement quality which cannot absorb or bind all the moisture content but leaves it as a future damaging force.

QUESTION- What is “too much water ” ?

ANSWER-  Depending on the quality and mixture, 3 % is “normal” water content in concrete. Every 100 gm of “free” ( which means not really bound) water content in 1 m2/ 5 cm concrete is 0.1 % of the concrete mass, which can be dangerous.

QUESTION- In what kind of climate is this criteria especially important ?

ANSWER- Such problems are independent of local climate. They can happen everywhere, depending on the local temperature and air humidity. But the mentality of the people regarding the construction requirements and the precautions that need to be taken can be different depending on the local environment. There is less or more sensibility regarding the damaging effects due to moisture in different places.

QUESTION- How should the moisture content be measured ?

ANSWER-In fact water has electro-magnetic fields, which is “sticking” all material, including construction materials,  water or moisture only can be measured, using electro-magnetic waves as the DNS-Denzel-Devices do.

It is important to to realise that all destructive measuring-methods destroy water or moisture also ! (BEFORE  the measurement has been done !)

All material (particularly human and animal,but also construction-materials) are "sticking together", because of electro-magnetic forces, which use water-molecules as "stickers" or "glue". Electro-magnetic forces or fields can only be checked using non-destructive, electro-magnetic, waves.All destructive measuring methods will show bad (too low) results, which may seem to be "good", but are actually bad and can actually be dangerous !

QUESTION- How long should one wait before installation of floorings or wall cladding before one can go ahead safely ?

ANSWER- Wait till a good and proof measuring device shows 3% on concrete-substrate or 1.5% on a cement-screed substrate. Depending on the local temperature and air humidity this can mean from 2 to 6 months depending on the thickness of the substrate.

Some concrete-materials (particularly cement) dry very slowly, and other kinds dry faster, but nobody knows how much time for each different kind of cement is needed to be “dry enough”, and  everybody thinks, that “just because there are a few drops of water left, still existing inside the concrete, there is no risk !”

And this is the reason, why we still have problems with moisture ! Nobody wants to wait till the water content is low enough for further applications !

QUESTION- Supposing a stone installation has already been completed and because of the moisture all these problems that you have mentioned , now start occurring. What can be done now ? What is the solution ?

ANSWER- When installations are done on wet substrates, nothing can be done, except re-install after waiting for the moisture to leave the substrate. Prevention, i.e., measuring the moisture content of the substrate BEFORE the installation, is the only way to prevent damages to the flooring or wall cladding.

QUESTION- How much is the cost ?

ANSWER- To do the new installation can cost up to 5 times the price of normal or first time stone installation, because many additional installations are done while the moisture is inside. So we are talking about very expensive mistakes that are being made.