Paul Igo, Technical Director at The Preparation Group, explains how to successfully remove adhesives and sealants to a achieve a seamless subfloor for tiling onto.

When preparing a subfloor to lay new floor tiles, the removal of old adhesives, sealants and other sticky substances has always been a challenge. Traditional methods are usually unsuccessful and have a tendency to generate surface heat, rendering the surface residue softer and stickier and displacing the adhesive rather than removing it.

Before you start, it is useful to know the properties of the adhesive or sealant that you are dealing with. How thick is it? What is its composition; soft, hard, very sticky? Things like the environmental temperature are a key factor, as at low temperatures adhesives can be brittle and at high temperatures even tackier. You must also consider the condition and composition of the subfloor and the surface profile that needs to be achieved in order for a new material to be applied – a second

— 20 — process may be required.

Thick, hard adhesives can be removed with milling flails fitted to the drum of a planing machine, but this method is less effective on soft sticky materials.

When removing tiles, scraping blades fitted to a multi-stripping machine will lift the underlying adhesives along with the surface material and any levelling compounds in one go.

However, the most effective method of dealing with adhesives, sealants and other sticky substances is by using a Grinding machine fitted with PCD (Polycrystalline Diamond) shoes. PCDs came to the market approximately 10 years ago and often aren’t considered or even known about.

The benefit of PCDs is that they scrape rather than grind to efficiently ‘lift’ these problem materials.

Polycrystalline Diamond is formed when diamond is sintered with a bond under high temperature and high pressure, resulting in a shoe with a longer life and high thermal stability. They generate less heat, so during the grinding operation their cutting edges remain clear.

There are plates onto which fit PCD shoes, specifically designed for 110v, 240v or 415v walk behind machines and the STG450 machine. PCD shoes can also be fitted to all machines with plates that hold standard grinding shoes and they are interchangeable with regular grinding shoes. In this way, a floor can be cleared of adhesives using the PCDs, and then cup discs fixed to the plate ready for grinding. To save time, the PCDs can be left attached ‘in the background’.

PCD shoes are available in Double Tooth, for the removal of thick

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