13/01/2021 – As well as for i balconies, even in the case of a Terrace you can talk about conservative rehabilitation (intervene without demolishing) when the pre-existing support does not present levels of degradation for which it is neither possible to recover nor repair it.
In this case the renovation of the terrace is finalized to restore the watertight function, or his waterproofing. Moreover, the cost incurred for this type of intervention is recoverable at 50% thanks to renovation bonus.
Terrace, how to assess recoverability
Given that the refurbishment is aimed at recovering the existing roofing layers, it is first of all important to establish what are the causes of the deterioration:
– natural aging process of the waterproof covering;
– use of unsuitable materials;
– bad execution of the installation;
– design errors in the stratigraphy.
The evaluation of the causes must be carried out by specialized professionals who will be able to determine the “recoverability” of the state of the places and therefore the feasibility of the conservation intervention.
In this Focus we will examine the case of a waterproof covering subject to the natural aging process, providing general indications for waterproofing with bituminous membranes.
Photo: bituminous prefabricated membrane COVER TOP©Winkler
Terrace, types of waterproofing membranes and laying systems
Waterproofing can be done with:
– self-adhesive membranes bituminous, ideal for cold laying, or glued;
– prefabricated bituminous membranes, including those self-protected or slated, ideal for the hot laying, that is with the use of flame.
Terrace, the assessment of water tightness
As already pointed out, the first step is to analyze the existing support. The cases that can occur are generally two:
Case 1) visible waterproofing mantle, ie unprotected, usually consisting of a bituminous membrane and characterized by the black color;
Case 2) non-visible waterproofing mantle, i.e. protected for example by paint, gravel, slate or paving.
Conservative restoration of the exposed waterproof covering
In the first case – waterproof covering without protection – we must distinguish between the following sub-cases:
Case 1.1) aged mantle but still waterproof, planar e snug to the support; in this case, having made, if requested, some preliminary repair operations (repairs of bubbles and / or small cracks) and an accurate cleaning, it is possible place the new waterproofing membrane in total adherence to support through the hot laying o la cold laying.
Case 1.2) aged mantle e no longer adherent: for example, there are significant folds across the juxtaposition lines of the membrane sheets, at the corners and near all the protruding parts such as chimneys, pipes, skylights, etc.
The presence of these corrugations assumes that there is moisture trapped between the layers. In this case the new waterproofing mantle must be laid in semi-adhesion, on waterproofing membrane strips and previously torch-bonded to the existing support; in this way, it is as if a micro-interspace is created that allows the trapped water vapor to diffuse without forming bubbles on the new covering.
Photo: bituminous prefabricated membrane BITULINE SMART APP© ONDULINE ITALY
Conservative restoration of the non-visible waterproof covering
In this case the new stratigraphy must be glued on the old protective layer. In the presence of a protective layer, it will be necessary to evaluate its maintenance status before proceeding with the installation of the new coating. Whatever type it is – slate, paint, floor – it is essential to check it adherence to the underlying support.
On a protected waterproof covering it is possible to proceed both with the hot laying with bituminous membranes, both with the cold one with self-adhesive membranes. In particular, if you opt for hot laying, you should try the sensitivity to heat on small surfaces, since the use of the flame could damage the existing one, creating detachments and injuries. In this case, a coat of primer before laying the new membrane.
Particular attention should be paid to the case of existing flooring: for overlapping on old floors, it will be necessary to check its anchoring; any loose tiles must be removed and the cavity grouted with rapid cement mortar. If the surface is crumbly it will be necessary to apply the primer.
In addition to the methods described above, waterproofing can also be achieved with liquid waterproofing, which is extremely elastic and capable of receiving new glued tiles, but we will talk more specifically about this in another Focus.
References: INDEX, Technical Specifications 3 “Conservative Refurbishments”
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