GOING UNDERGROUND
As rising damp from the subfloor can spell disaster for tiling installations, BAL discusses how a damp-proof membrane can protect a finished floor.
The number of planning applications for basement extensions has risen by 183% according to research by Halifax bank, therefore it’s essential that tillers are aware of the potential for moisture issues which can cause a floor to fail.
Adhesive failure, staining, discolouration and efflorescence can all occur due to moisture emanating from the subfloor, so it is crucial that the final finished tiled floor is protected from the damaging effects of moisture from below with a Damp Proof Membrane (DPM)
Surface damp-proof membranes, like new BAL DPM, will protect tile adhesive and tiles from both ground floor water and residual construction moisture found in new screeds such as sand:cement and calcium sulfate screeds.
As a rule of thumb, to achieve a moisture content of 0.5% water by weight (Carbide Bomb test) the drying time for a calcium sulfate screed – is approximately 1mm per day up to 40mm thickness under ideal site condition. Direct to earth cement:sand screeds will also require a DPM.
One solution is BAL DPM which acts to control moisture and allows for the early application of a levelling compound or tile adhesive.
BAL DPM can be applied onto a new cement:sand screed once the moisture content is below 98% RH as measured using an hygrometer. It can be applied to new calcium sulfate screed once the moisture content is below 87%. Please note it is important to obtain the screed manufacturer’s confirmation that the screed is compatible with a DPM and does not contain any additives that may reduce adhesion between the screed and the DPM.
Before laying the DPM, ensure that all screeds are well-prepared and flat, with any laitance removed.
As well as basements and cellars, a DPM should also be considered for other projects where a structural damp-proof
40 | SUBFLOOR PREPARATION
membrane is not present or is ineffective. This is likely to be the case in refurbishment projects involving buildings constructed pre-1970, where the installation of an effective structural damp- proof membrane was not a requirement of the building regulations.
BAL DPM is also suitable for balconies, terraces and patios which are due to be tiled, dependent upon design
consideration. A DPM on an external tiled area will protect moisture sensitive stone such as granite from staining due to rising ground floor water, as well as rain water. For external tiled areas, we would always advice on the use of a capillary passive drainage system like BAL’s new external tiling systems which ensure the rapid drainage of tiled surfaces.
As well as external areas, BAL DPM can be used in industrial installations that require resistance against dilute chemical spillages or pollutants such as chemical plants or manufacturing units.
Unlike other DPM systems, BAL DPM is also suitable for walls, as well as floors, as it is resistant to hydrostatic pressure. Refer to the Technical Data Sheet for detailed application instructions.
As a multi-purpose product, BAL DPM can also be used as a one coat primer or as a two-coat waterproofing system. When sand-blinded, BAL DPM allows tiling onto difficult substrates such as steel.
As a waterproofer, BAL DPM is an easy two- coat system when used with BAL Self-Adhesives Butyl Tape in corners and junctions.
For detailed application instructions as a primer and waterproofing please refer to the BAL DPM Technical Data Sheet.
www.bal-adhesives.com/newproducts www.tomorrowscontractfloors.com
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