search.noResults

search.searching

saml.title
dataCollection.invalidEmail
note.createNoteMessage

search.noResults

search.searching

orderForm.title

orderForm.productCode
orderForm.description
orderForm.quantity
orderForm.itemPrice
orderForm.price
orderForm.totalPrice
orderForm.deliveryDetails.billingAddress
orderForm.deliveryDetails.deliveryAddress
orderForm.noItems
CALCIUM EFFICIENCY F. Ball advises contractors on using specialist levelling compounds for calcium sulphate screeds.


Calcium sulphate screeds are an increasingly common choice of subfloor in new builds, especially where underfloor heating is incorporated within the subfloor. This is because of the speed with which they can be applied over large areas and other advantages over concrete bases, including less shrinkage and fewer joints required within the subfloor.


Manufacturers of these types of screeds advise that a calcium sulphate-based self-levelling compound is used when dealing with this type of subfloor. If cement-based products are applied onto calcium sulphate screeds, particularly in damp environments, it can result in a chemical reaction that causes the formation of ettringite, a crystalline material, where the two materials meet that can cause floor failure.


Levelling compounds such as F. Ball and Co. Ltd.’s Stopgap 1100 Gypsum have been developed to offer maximum compatibility with calcium sulphate screeds. Unlike most cement-based products, Stopgap 1100 Gypsum is virtually tension free and does not shrink during the drying process, which limits the amount of stress at the bond interface. As well as providing a specialist solution for the levelling of suitably prepared calcium sulphate screeds, the product can be effectively used over a wide range of surfaces including waterproof surface membranes, concrete and sand/cement screeds.


HOW TO PREPARE When installing new floorcoverings over calcium sulphate screeds, it is essential to follow the basic principles of subfloor preparation, while considering a few critical points to avoid common causes of floor failure associated with this type of substrate.


Just as when preparing other subfloor types, the first step in the process should be to ensure the subfloor is suitably sound, smooth and dry. This often means beginning with the mechanical removal of laitance (the crust of fine particles formed on the surface of the screed as it dries), which should be undertaken by the screed supplier, seven to 10 days after the screed is installed, when the laitance is easier to remove. However, the process is frequently left to the flooring contractor, allowing the laitance time to harden, and prolonging the drying time of the subfloor.


If not removed, laitance can cause a subsequently applied levelling compound to debond from the substrate, potentially causing floor failure. Any other contaminants that may prevent adhesion, such as wet trade waste or debris, should also be cleaned off.


DRYING TIME A moisture measurement test should then be conducted to ascertain if the subfloor is dry enough to proceed directly to installing floorcoverings. If a subfloor has a relative humidity (RH) reading above 75% (or 65% if wood floorcoverings will be installed), contractors will need to allow further time for the screed to dry, otherwise there is the risk that excess subfloor moisture will attack floorcoverings, resulting in floor failure.


22 | LEVELLING COMPOUNDS


Calcium sulphate screeds dry from the bottom up, so a moisture test may deliver a positive reading right up until the point the subfloor is completely dry. Therefore, contractors should be patient when allowing for the subfloor to dry sufficiently. This process can be accelerated by ensuring areas are adequately ventilated, by opening windows or using a dehumidifier, and/or turning on underfloor heating, if incorporated within the subfloor, at a low temperature.


PRIME IMPORTANCE The application of a primer is also required in almost all circumstances to promote adhesion of subsequently applied subfloor preparation products and stop the rapid drying of levelling compounds when applied over absorbent subfloors. It also prevents pinholing, caused by tiny bubbles resulting from the slow escape of air from the subfloor, which burst on reaching the surface, leaving small pinholes or craters as the levelling compound cures.


F. Ball’s Stopgap P121 primer is specially formulated to promote the application characteristics of compatible levelling compounds when applied over calcium sulphate screeds, which are denser than concrete or sand/cement screeds – it contains finer particles than other primers in the F. Ball range, helping it to bond with calcium sulphate screeds. The product should be applied in two coats; the first diluted with one part water to one part primer, followed by a second coat applied neat.


FINAL THOUGHTS As calcium sulphate-based levelling compounds typically take longer to dry than other, cement-based products, contractors should be prepared to wait up to 24 hours before installing textile floorcoverings, and up to 48 hours before installing resilient floorcoverings. Further, underfloor heating must be turned off at least 48 hours prior to, and throughout, the application and drying of the levelling compound, and the temperature of the subfloor should be kept above 10°C from start to finish. Once the levelling compound has cured, specified floorcoverings can be installed using a suitable adhesive.


www.f-ball.com


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50