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Asphalt/Bitumen Solid Floor, DPM and Screed

Discussion in 'Floors, Stairs and Lofts' started by GtYSPmLAqM8W5pLH, 26 Sep 2021.

  1. GtYSPmLAqM8W5pLH

    GtYSPmLAqM8W5pLH

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    Long time reader, first time poster. Having read the sticky threads regarding liquid DPM and self leveling for concrete, I have an understanding of what is required, but would rather hear some opinions on the current floor surface if possible!

    Property is mid 1960s, solid ground floor. When stripping the bathroom, the area under the bath tub was bare concrete, lower than the rest of the "black" floor throughout the property. I am assuming its asphalt with a bitumen top layer, 10-15mm thick. It stops around 10mm away from the internal walls in all rooms.

    It is not attached to the concrete floor below it in any way, and is very brittle, it comes up easily in large sections. Considering half the bathroom was already missing, and a wall was being removed, I took up the rest of it in that area to reveal the concrete slab.

    There was a thin strip of DPM under the block internal wall as shown in the attached picture (it was lapped under the asphalt/bitumen on both sides). Does the asphalt/bitumen floor act as a DPC in this case, considering a strip of DPM was under the internal block wall?

    IMG_20210730_202157.jpg IMG_20210730_202151.jpg

    Sections of the asphalt/bitumen is missing in the original kitchen, where I can only assume a cooker once was or similar. The kitchen wall is also being removed, which will leave another gap in this surface.

    The size of the room will be approximately 26sqm. I'm considering removing the asphalt/bitumen as it comes up so easily and breaks up, so I have a bare concrete floor to work with. There is no evidence of damp at the moment.

    Would a liquid DPM be recommended (or other form of DPM) in this scenario if my assumption is correct the asphalt/bitumen was acting as a DPM? Before fresh self-leveling/screed? The floor is going to be tiled.

    Any advice would be appreciated. Thanks!
     
  2. RandomGrinch

    RandomGrinch

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    Sorry, not relevant to your question.
    However, it might be worth being a bit careful when dealing with the 'bitumen', some of the stuff that was used to hold down parquet floors did contain asbestos.
    There's not a big risk, but be wary!
    It may be worth getting a sample tested?
    But others may have different opinions :)
     
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  4. JobAndKnock

    JobAndKnock

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    The pattern on that bitumen together with the age of the house (mid-1960s), use in the kitchen and missed areas (e.g where the free standing cooker was) are all indicative that there wasn't parquet on the floors and that it isn't a DPM. I believe that what is on that floor is probably Marley (or similar) vinyl or linoleum tile adhesive and the imprints on the floor are actually from the hessian backing these tiles sometimes had. They were used all over the place in the 1960s, particularly on the ground floors of houses. So, NOT a DPM

    You are right about one thing, though, that adhesive very often did contain chrysotile asbestos fibres, so I'd get it tested.

    if it does contain asbestos it should not be abraded (or walked on) and it will need to be well damped down before removal. P3 masks are a must when dealing with it and waste must be double bagged and disposed of correctly - not just put in with ordinary household waste or builders rubble (the local council can provide appropriate bags and remove them for proper disposal)

    Chrysotile is the least dangerous form of asbestos, but should still be handled with care to reduce the chances of fibres becoming airborne, hence the recommendation to damp down. I'd also suggest that wearing a head to toe disposable coverall, showering immediately after removal of materials and washing of clothes worn beneath the coveralls in addition to wearing an appropriate mask are highly advisable. DO NOT USE A DOMESTIC VACUUM OR A BRUSH TO REMOVE DUST - both will result in asbestos fibres becoming airborne
     
    Last edited: 27 Sep 2021
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  5. GtYSPmLAqM8W5pLH

    GtYSPmLAqM8W5pLH

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    Thanks for the information, I'm aware of the asbestos risk/precautions to take etc, this property also had artex ceiling coverings (which have all been removed and disposed of professionally).

    I should have took a picture side on - the black layer is probably 5mm thick, and the (what I would call asphalt) is around 10mm thick under it. Not attached to the concrete in any way. Was this construction used as a type of insulation/sub floor back then?

    Is the black layer bitumen? Then they would have used adhesive on top for whatever tile was there, which is what may contain asbestos? (the pattern is only visible in one room, the kitchen).

    The other rooms, the black (bitumen?) is completely smooth with no pattern, where carpet previously was. I was going to leave this as is, considering it is in good condition and only having carpet elsewhere again.

    Regarding the DPM under the (removed) internal wall, is it possible they just did this for good measure, and the actual concrete slab of the house has its own DPM? There is no evidence of damp anywhere.

    I will remove the kitchen bitumen/asphalt with the recommended precautions above with it having parts missing (and being made into one room). In this case would self leveling compound on top of clean concrete just suffice?

    Thanks
     
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