DPC - should I bother?

[jon4727]

I am renovating a 1950's semi (ex-council). The ground floor is a concrete slab with marley tiles, stuck down with a thin layer of tar-like material. Basically like in these threads:

https://www.diynot.com/diy/threads/concrete-floor-with-bitumen-paint-more-bitumen-or-seal.486497
https://www.diynot.com/diy/threads/rising-damp-from-concrete-floor.471076/

I want to:

• Remove the tiles, exposing the tarry concrete.
• Paint on a sealant of some kind to ensure no asbestos fibres are released from the tar.
• Install underlay and laminate flooring directly on top.

This assumes the concrete slab is in a decent condition and fairly level, which I think it is.

I havn't mentioned adding a DPC. From what I understand, in the original build there was either no damp proofing layer (natural evaporation was relied upon to prevent water buildup, or the tar and tiles themselves acted as a crude DPC, explanations differ). In my house there are areas where the tiles have already been removed, and no damp is evident. The question is: do I really need to put down a DPC (which would also presumably need priming and screeding on top) if the concrete is in a good condition?

 

[footprints]

Leave the tiles alone and just lay laminate with suitable underlay (many include a vapour barrier anyway) under it.


The best thing to do with asbestos tiles is ..... nothing, just leave them undisturbed.

 

[dazlight]

Leave them down or take up and

Ardex NA
Dpm1c
Then lay laminate with a decent underlay.

 

[Notch7]

One of my neighbours recently had a flood.

The loss adjuster came, agreed to the work.

Work started and the tradesman took up the carpets, then looked at the tiles and wondered if they could contain asbestos.

Insurer got it tested, found to be positive.

My neighbours had to move out completely, empty the house and move into holiday inn.

it took 3 months

 

[dazlight]

That’s crazy. You can uplift them yourself as very low risk.
Try to take them up in big pieces & double bag them.

 

[jon4727]

I have informed myself about health risk reduction methods for DIY removal of these tiles and I am confident about this part of the job. I want to remove them because:

1. Some of them are starting to get damaged around the edge of the room. This will get worse when I pry off the carpet grippers.

2. I won't really know what state the concrete is in until I lift them. There may be a few small pits or voids which should be filled in.

3. They are about 4 mm thick, freeing up this wasted depth would give more options on what flooring to lay down.

4. I don't like the thought of them still being there when everything is finished.

There is a lot of good info available, including on this forum about what products to use and in what order, if I decide to lay down a DPC and screed. What I am less certain about is knowing when it is absolutely necessary! The sticky thread mentions using a flooring hygrometer to check whether the moisture is above or below 75%, and that as long as it is less, I might not need a DPC. Is this criteria what most professionals would agree with? Are there any special considerations I need to make when carrying out this test (e.g. length of time, number of locations, ambient conditions, central heating on or off, weather, time of year)?