Gary Haigh, ARDEX Group training and technical support manager, elaborates on the importance of installing smoothing and levelling compounds correctly
Smoothing and levelling compounds help level up small surface irregularities on new and existing bases and usually come in one-part or two-part forms. Easily mixed and simple to apply, they find their own level, giving a smooth finish for laying tiles or other floorcoverings. Before laying a smoothing and levelling compound, it’s essential to ensure that correct subfloor preparation is carried out.
Firstly, ensure the surface is clean, firm, dry and free from grease, dust and any other contamination which may be considered barriers to adhesion. Any new concrete or screed must be left to fully cure according to the manufacturer’s instructions before applying any levelling compound. Ensure any direct-to-earth subfloors incorporate an effective damp-proof membrane such as ARDEX DPM, or DPM 1C. Many subfloors will also need priming. Floors such as concrete, cement:sand screeds, anhydrite screeds, cement:sand screeds with underfloor heated screeds and suitably constructed suspended timber floors.
Priming ensures the levelling compound fully adheres to the substrate, as well as extending the open times of levellers on porous floors. If levelling over timber boards where the joints are open, we suggest using thin heavy-duty tape to bridge the gaps. When mixing your smoothing or levelling compound, always ensure you follow the manufacturer’s instructions. We recommend mixing with an electric drill mixer with a suitable “cage” mixing paddle usually 600-1000rpm. Always mix until a lump-free mortar is achieved and allow the mixed leveller to stand for two minutes before remixing for 30 seconds, if stated on the product data sheet.
Once the required consistency is achieved, pour the mix over the prepared substrate and spread to the required depth using a suitable steel finishing trowel or long handled blade. Work the mixture well into the corners, edges and around projections. When you’ve finished spreading the mixture on the floor, pour some more mixture onto the floor, spread it out and blend it in with the previous area. Before allowing to cure, ensure the surface is sufficiently smooth to receive floorcoverings without any further treatment.
If you’re laying tiles or slabs, floors should be corrected to SR1 (surface regularity). This is plus or minus 3mm or less over a two-meter straight edge. We wouldn’t recommend the use of spiked rollers on a fibre-reinforced product such as BAL Level Max as this can pull fibres through to the surface, however a spiked roller is useful on non-fibre products such as ARDITEX NA to dissipate any air bubbles trapped in the compound. If any trowel marks do remain, rub down before the compound has hardened.
Always allow the new floor to set before laying your finished floor surface. Setting times can vary depending on your chosen product normally between 4 to 24 hours and is dependent upon your floor finish. For example, BAL Level Max can be tiled after 4 hours at any depth – even at 80mm. For an even faster install, you can choose a rapid-setting leveller such as BAL Level Fast, or ARDEX K 55 Fast – these super-fast setting compounds can be tiled in roughly 45 minutes and 60 minutes respectively. In wet areas allow a minimum of 24 hours before waterproofing the levelled screed with a tanking system such as BAL Tank-it, BAL Waterproof 1C or ARDEX WPC.
Finally, we would always advise checking with the manufacturer or their technical advisors for before application advice to ensure project success and to consider any performance benefits specific products may provide. For example, most smoothing and levelling compounds can only be applied up to 30-40mm and will need to be used in more than one application or with other materials required. However, there are some exceptions on the market such as BAL Level Max which can be applied from 2mm to 80mm in one application. It’s important to remember that most levelling compounds aren’t suitable as a finished, wearing surface, and they should always be covered.
There are some exceptions, for example ARDEX K 301 and ARDEX K 71 which can be used as a finished surface. Typically most smoothing and levelling compounds are suitable with most screeds, including sand:cement, anhydrite and flooring grade asphalt. However, when levelling timber floors, or screeds containing underfloor heating, only fibre-reinforced products are suitable, such BAL Level Max or ARDEX K 40 HB. When levelling over difficult substrates such as bitumen, tarmac, steel, and damp concrete, specialist solutions should be used such as ARDITEX NA.
Covering the whole of the UK, ARDEX Group training and technical support managers offer practical knowledge and onsite consultancy and training to tiling and flooring contractors. If you’ve experienced a problem on your installation whatever brand you’ve used, you can trust our TSMs to offer dependable solutions and remedies. What’s more, we’ll even send samples away for independent analysis at our laboratories to find the cause of the problem.
03330 030160
www.ardex.co.uk
