The right foundation for long-lasting floors

Long-last­ing suc­cess is usu­ally based on a sound found­a­tion. Just like ath­letes start by build­ing up their endur­ance and their muscles, also house con­struc­tion starts with lay­ing the found­a­tion. The same applies to the sub­strate: Care­ful sub­strate pre­par­a­tion is the found­a­tion of suc­cess­ful floor­ing install­a­tion. Fail­ure to do so may res­ult in later dam­age to the floor. Repair work is not only time-con­­sum­ing but also expens­ive.

A major issue in many homes is the replace­ment of old floor cov­er­ings. The musty car­pet needs to be removed and the out­dated ceram­ic tiles must give way to high-qual­ity par­quet, trendy lux­ury vinyl floor­ing or mod­ern large-format tiles. The first thing to do is to com­pletely remove the old floor cov­er­ing – includ­ing any adhes­ive residues. Before installing the new floor­ing, the sub­strate must be care­fully checked. A few simple cri­ter­ia can help.

The key factor for achiev­ing good res­ults is an abso­lutely even sub­strate. If the screed does not have a level sur­face, floor­ing mater­i­als like par­quet or lam­in­ate may later break if there is a hol­low space under­neath. Car­pets and vinyl or PVC floor­ing are able to adapt to uneven­ness, but the res­ult­ing bumps are not a pretty sight – and can even pose a trip­ping haz­ard. In gen­er­al, it is advis­able to firmly bond the floor­ing over the entire sur­face. This makes it more robust, hard-wear­ing and dur­able. A level sub­strate ensures that there is a firm and reli­able bond between floor­ing and sub­strate. It also reduces impact sound and enables effect­ive heat trans­fer from the under­floor heat­ing sys­tem. If, how­ever, the sub­strate has cracks, holes or oth­er defects, a lev­el­ling com­pound or filler is neces­sary to provide a sur­face of uni­form even­ness.

Just as import­ant is the strength of the sub­strate. Oth­er­wise, there will be a risk of adhes­ive fail­ure. The easi­est way to determ­ine the strength is the so-called grid scratch test. A poin­ted met­al object (e.g. a nail) is used to scratch a rhom­bus (#) into the sub­strate. If there is no flak­ing along the edges or where the scratch lines cross, the sub­floor is of suf­fi­cient strength.

When plan­ning the install­a­tion of floors in a newly built house, spe­cial atten­tion must be paid to the floor mois­ture. In new-builds, the resid­ual screed mois­ture is often under­es­tim­ated. If the screed is not suf­fi­ciently dry, its mois­ture not only impairs the adhe­sion of the floor­ing adhes­ive but, in the worst case, also pro­motes the devel­op­ment of mold and odor. New screeds are not always ready to receive floor­ing after four weeks – this is just the lower time lim­it. How quickly the screed dries strongly depends on factors such as air humid­ity, ambi­ent tem­per­at­ure and thick­ness of the screed slab. It is there­fore highly recom­men­ded to have the sub­strate pre­par­a­tion done by a pro­fes­sion­al floorer. If you prefer to lay the floor your­self, you should at least ask an expert to check the resid­ual screed mois­ture. Before bond­ing the new floor cov­er­ing on top of the expertly pre­pared sub­floor, it must be care­fully cleaned. Make sure to sweep or vacu­um the sur­face so that no remain­ing dust or dirt particles can impair adhe­sion.