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Dealing with movement joints

Using a real-life example, Jason Tatton looks at issues arising when installing floorcoverings where movement joints are present.

AT F Ball’s technical service department, where we provide advice on the best course of action for a particular flooring refurbishment, one of our tech reps recently responded to a request for advice regarding floorcoverings that had reportedly begun to lift in a recently refurbished hospital A&E department.

On visiting the site, he saw that the failure followed a straight line, creating a ridge in the newly installed vinyl sheet floorcoverings, which covered a total area of about 120sq m.

The issue
An underside inspection of one area found that the raised vinyl corresponded with a 20mm wide movement joint, which had been filled with a smoothing compound as part of works prior to the refurbishment.

Movement joints (also called expansion joints) are spaces that are commonly and deliberately incorporated into a building’s structure, including its floors, to allow it to accommodate stresses and strains exerted by movements as a result of heat, moisture and environmental forces.

Movement joints are also usually filled with a flexible material, such as a polysulphide filler, which absorbs compressive forces without damage and prevents ingress of dust and debris, which could render the joint ineffective.

Where movement joints are situated, a flooring installation should be terminated either side of the joint and a suitable proprietor treatment joint should be installed – subfloor preparation products and floorcoverings should not be installed over the top, otherwise the floor may rupture. Not only will this look unsightly, but it may also produce a trip hazard.

It’s always advisable that a flooring contractor consults a structural engineer or site plans to find out the location of joints, especially where they’re not visible, because they may be hidden by previous work, as in this case.

The solution
Based on this assessment, the tech rep was able to recommend remedial work to be undertaken either side of the joints rather than removing the entire installation and starting again.

It was advised that flooring contractors begin by lifting the affected sections of floorcoverings and remove all materials applied directly over the joints. Following guidance, the smoothing compound was cut back at both sides of the joints to expose some of the waterproof surface membrane, which was assessed to be intact, well-bonded, clean and dust-free.

Subsequently, it was recommended that subfloor preparation products should be reapplied up to the edges of either side of the joint, this involved first the application of Stopgap 1200 up to the level of the waterproof surface membrane. The movement joint should be cleaned out, ensuring it’s dust- and debris-free, then a polysulphide filler should be applied.

Final steps
The surface was then primed using Stopgap P141 before another layer of Stopgap 1200 Pro was applied to bring the areas that were being repaired to the same level as the rest of the floor and create a base for the receipt of new floorcoverings.

When the smoothing compound was dry, safety flooring could be installed over the repaired areas, either side of the expansion joints, using F Ball’s Styccobond F44 solvent-free acrylic emulsion adhesive. The seams between the new and previously installed vinyl sheet floorcoverings were welded to maintain a watertight seal required in the clinical setting.

Lastly, suitable expansion joint covers were installed to provide an aesthetically pleasing finish.
Jason Tatton is technical services officer, F Ball and Co

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