Self levelling, should I scrape off old tar?

[compact]

Self levelling concrete floor.
It has old dry tar probably from the 50's for parquet.
I'm levelling for wfh overlay panels. Should I wire brush, Stanley wallpaper scraper scrape it off. It's well down however wondering if wfh could get it up and it break up, causing some delamination from the concrete and affect tiled floor.
Or am I over thinking things?

 

[TicTac]

If some of it's coming up, then the rest is in danger of doing so as well. It'll be hard work, but get up as much as you can. Try a floor scraper.

 

[Tigercubrider]

It may have been to hold down parquet but also been the dpc?
It is in my house

I have a big Harris scrapper, and found when I was cleaning parquet for repairs, that white spirit dissolves the bitumen - test an area dry then moistened

 

[KenGMac]

compact, good evening.

I would advise extreme caution.

That "Old Tar" will be in all probability the Damp Proof membrane that is stopping the ground water from getting into your home?

That material is probably Mastic Asphalt removal could cause long term problems with rising damp??

I for one would not advise its removal

 

[TicTac]

But it's coming up already, and it's a potential delamination issue, so needs resolving; but you could be right, it may well be a dpm as well as a glue for the old parquet or tiles.

You need to test the floor compact, and see if there's moisture in it. Either with a meter, or a square (30x30cm) of plastic taped to the floor with duct tape, and see if there's any moisture under it overnight.

 

[compact]

Thanks for the replies. It's a suspended slab so little path for water to rise and dry as a bone in the crawl space under.
It's very patchy as you can see from the photos as the , so no longer effective. Plus the parquet has been loose which does take it up, however no damp
.

 

[bobasd]

it could be a damp membrane if it was spread with a smooth edge trowelbut it was spread with a notched trowel. but the notches run all over instead of in one direction for laying block and theres no signs of a block pattern.
have you lifted ceramic tile only or is there any 12"x12" plastic tiles?
a big heavy scraper like the sf roughneck will lift most stuff. so will tapping the black stuff with a hammer to shatter small sections at a time.
you wont need a perfect surface but have a look for damp issues on the floor and the edge walls.

 

[compact]

Picture under the floor

 

[KenGMac]

OK not a Damp proof membrane, it is the bituminous glue for the parquet

Should be OK to remove, but will probably need a self leveling screed to get to a suitable surface finish and indeed level to the [no doubt] various doors entering this room.

As an aside, if there is a really good void below the Bison slabs on the ground floor it may be worth consideration to install slab insulation to the underside of the Bison Concrete Plank floors??

 

[dazlight]

Grind it off, try remove 75% of the adhesive.
Prime and screed with Ardex NA or fball 1200 pro

 

[compact]

It's tough and horrible job.
I've tried a blade scraper and a wire brush on the grinder. It comes off just about but horrible dust in the air.
I am half thinking if it's this tough to get up, then it's never coming up. It's been there 60+ years
Plus the wfh won't realistically heat it up enough to get it to unstick or break apart, surely

 

[myuserid]

I had a similar issue with a house I was doing up recently. Tried grinding the old bitumen off, but that took forever and was a messy job.

I would knock any loose stuff off - remove as much dust as possible and buy Ardex NA which is a 2 part SLC. It's expensive, but saves a lot of work and no need to worry about your floor lifting afterwards!

 

[Tigercubrider]

If dust is the only issue , get a workshop vac and adapt it to suck the dust at source , before it gets airborne. Mine is an aldi and eliminates 90%

 

[compact]

Yep quite dusty just cracking on. Don't want to do this again