Times When You Can Cut To The Chase
Jonathan Baxandall on rebate, anchor point, toe-in and chase
REBATES, anchor points, toe-ins and chases. We are all probably familiar with these different terms, but when considering the floor preparation required prior to receiving a synthetic resin topping, my experience is that their importance can often be overlooked.
Although the terms can mean slightly different things to different people, essentially they all refer to a cut or channel made in the substrate into which the resin is dressed.
Many are familiar with the concept that when a PU Crete type product is to be installed then a rebate will be required in the substrate.
What people are often less familiar with, is their use and function when an epoxy screed or flow system is to be installed. A rebate cut into the substrate into which the resin is dressed can improve the durability of the installed system in several ways.
I Mechanical anchor: This is especially important when PU Crete systems are installed to distribute the curing stresses of PU Crete and stop them from peeling themselves up from the substrate during the curing process.
I Avoid weakness at vulnerable zones: Most resin systems over 1mm in thickness are vulnerable to cracking and delamination at transition points, if left as a free edge. For example, damage can often be seen in a busy doorway if the resin has been left as a feather edge.
Finishing the resin product, PU or epoxy, into a rebate at these points can greatly improve durability of the system as the extra resin contained in the rebate helps distribute loads and stresses received during ser vice that would other wise crack or delaminate a free edge.
I Preventing ingress of aggressive media to the substrate: Dressing the resin into a rebate alongside a gully or at cove edges will give the system greater durability in areas where it is always wet and will help stop the water (or other chemicals) from getting under and then lifting the resin system, in comparison to a system finished without a rebate.
I Correct placement and rebate size are also important. Consider a rebate at all of the following places: At
edges, parallel to expansion joints, at thresholds, feather-edges, at free edges of a cove, where dissimilar flooring materials join and at day joints.
For heavy traffic a rebate may typically be equal to the thickness of the flooring in depth and twice the thickness of the flooring in width, for example for a flooring 5mm in thickness, the rebate cross-section should be 10mm wide and 5mm deep.
With flow applied floorings it is normally sufficient to make a single concrete saw cut up to 5mm deep into which the flooring should flow, to terminate at the edge.
Jonathan Baxandall is with Altro technical team
T: 01462 489405
This article has been reproduced from the Contract Flooring Journal website. You can find them at www.contractflooringjournal.co.uk.