What to look for in refurbishments

What are the key aspects in refurbishment projects and what challenges are presented to a flooring contractor when undergoing such works? Martin Cummins has the answer.

AS technical manager for Bostik Flooring, part of my role is to offer support and training for the technical team and the flooring sales team. Fortunately, at Bostik we’ve an energised and enthusiastic team with a desire to learn, so the training days can be very rewarding.

However, deciding on what training is needed and what level to pitch it at can be a little tricky because of the old adage of ‘I don’t know what they don’t know, and they don’t know what they need to know’. The topic of refurbishments is a perfect demonstration of this.

So, what are the key aspects in refurbishment projects and what challenges are presented to a flooring contractor when undergoing such works?
The first thing to assess is the likely age of the building.

This is key to how the construction was likely to have been carried out. If it was post-‘70s then there is a likelihood a base DPM may have been utilised in the building construction. That is, if the building was designed as habitable (ie not a factory, warehouse etc).

Pre-‘70s construction generally didn’t include any need to use a base DPM.

The next thing to evaluate is whether the refurbishment is on an upper floor or a floor in contact with the ground (ie ground floors, lower ground, basements etc).

If it’s an upper floor then unless leaks from plumbing, showers, toilet blocks etc have been present, the subfloor is likely to be dry, while ground floors in old buildings (see previous note) can be considered as ‘direct to earth’, and therefore there’s potential for moisture to migrate into the building.

Point of interest: The validity of moisture testing on refurbishments is sketchy. The results only mirror the status of the subground and subfloor on the day of test. In summer it’s very likely to show dry but come winter when the land is heavier in moisture and the heating is on in the building, then moisture migration can be very significant. If you get a wet reading you need a surface DPM. If you get a dry reading you need a surface DPM unless it can be determined that there’s a base DPM in the building.

Ideally, and as was found to be the case in Europe presently, floorcoverings should be removed to return you to a sound, strong original base. However, in the UK many contractors don’t see things in such black and white, meaning there’s often a desire to limit preparation.

So, the next thing you may need to assess is what present flooring MAY be left in place and what MUST be removed.

For example, a sound, solid terrazzo floor is in itself a good surface. This can be cleaned up and DPM’d on a ground floor or suitably primed on an upper floor before applying the smoothing compound. Quarry tiles or ceramics are similar, although grout lines make these a bit more difficult to DPM successfully.

The caveat with leaving flooring in place is we/you can only offer assurance our materials will bond to the substrates. If they work loose or the adhesive they were set in breaks down, then it’s not our failing or responsibility.

Moisture sensitive floorings such as Granwood and magnesite cannot be left in place on any direct to earth areas so have to be uplifted. On upper floors they can be suitably prepared, primed and an appropriate (usually low tension) smoothing compound can be applied.

Resilient sheet and tile flooring should always be removed. On ground floors it’s best practice to also get rid of adhesive residues and previous smoothing compounds and surface DPMs to get back to a sound, strong base.

On upper floors you’re likely to leave a smoothing compound with adhesive residues. These may have been laid 20 years ago when products were very different to today.

Typically smoothing compounds were ‘latex’, high bonding, low compressive strength products. To ensure no undesirable stress and tension is created, we always advocate a low strength, low tension product be used over the existing smoothing compound provided it appears sound.

Be careful if leaving adhesive residues that these are able to receive the chosen smoothing compound.

Problematic residues may be very resinous and powder up easily, very soft, or they may be affected by moisture from the smoothing compound. Always consult the manufacturers’ technical teams wherever there’s doubt. Don’t skimp on smoothing compound thickness - the smoothing compound will in isolation be the absorption medium and strength for the entire floor.

Due diligence needs to be carried out when removing thermoplastic/crunchy tiles as these may have contained asbestos. The bond was usually with a bitumen adhesive, but this was not there as a DPM so don’t consider the building as being protected from moisture just because of a black adhesive.

On ground floors, epoxy type surface DPMs are not going to offer a very strong bond to bitumen, so pre-smoothing with a suitable smoothing compound that’s capable of performing on bitumen and in a damp environment is an option, otherwise a specialist tool for mechanical removal of the bitumen is the best route.

Wood block and parquet flooring will also have had bitumen as the adhesive, so the same approach is recommended as with thermoplastic. If leaving the blocks in place on upper floors, our advice is to overlay with SP101 grade plywood or equivalent rather than trying to clean down, prime and smooth.

Cork may be found on both ground and upper floors. Its moisture sensitive nature and compressibility mean that in all cases you should get it uplifted.

Carpet tiles will have been laid onto a tackifier adhesive. If relaying carpet tiles, it’s feasible to clean up the floor and apply a fresh coat of tackifier. If changing flooring type, then a new smoothing compound needs to be applied. Generally, they can affect the residues, so removal is preferred, unless the manufacturers can state the chosen product will bond to and not affect carpet tile tackifier.

This is just an introduction into what to look for. Existing screeds, asphalt, infill of trenches and service ducts, painted floors, carpet backings – there’s no crib sheet or ‘one-shop-fits-all’ approach. It’s an ongoing learning curve for us all, so when considering refurbishment look once, look twice and then look again. Ensure you’re not missing anything and don’t be bullied into just putting a smoothing compound on top of ‘it all’ because the builder says so. You’re the professionals.
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