Bitumen query.

[roundthebend]

Sorry if this is draggin up old ground. I've read and heard conflicting info.

I'm a DIYer with a very small (just over 1m sq) floor to tile. The previous vinyl tiles have been lifted and left some bitumen behind.

EDIT: on reading some other posts it seems that this bitumen can be a few millimetres thick at times. Mine is just a wafer thin layer onto concrete, but definitely smells like bitumen. And there's one small area where it is quite thick, but that's going behind boarding so won't be tiled onto.

Some say it has to be scraped off.
Others say to use SPF adhesive and it can go straight on without scraping it off.

Then I asked in a tile showroom and was told to get most of it off, then PVA, then use their rapid set adhesive. Yet I've heard that PVA isn't a great idea.

At this rate, I'm beginning to think that there's no right solution and I may as well just bash on with it however I see fit.

 

[mypetearthling]

I've always told my customers that their best bet is to remove what they can, then use primer either of the same brand as the adhesive or the one the adhesive manufacturer recommends.

(Although it has to be said that more than one person has gotten bored of removing the bitumen and just primed and tiled on top, so far they haven't come back needing to re-lay the floor! )

The 'grab' of flexible adhesive is always better that a normal fast set.

K

 

[Richard C]

Remove as much of the bitumen as you can with a scraper, do not use a heat gun or any form of solvent as it will reactivate the bitumen & cause adhesion problems. Use an acrylic primer & tile with flexy addy.

DO NOT use PVA on any tile base.

 

[roundthebend]

Thanks for the info chaps.

So, my local tile store may have given me poor info about using PVA to prime. I've read a lot of debate about that but the majority vote seems to be that PVA isn't reliable enough compared to purpose made primers.

Can anyone suggest a suitable tool for scraping? My wallpaper scrapers/filling knives aren't strong enough and my screwdrivers are too small to get the job done this side of the London Olympics!

 

[Richard C]

So, my local tile store may have given me poor info about using PVA to prime.

Yes & it’s well documented.

I've read a lot of debate about that but the majority vote seems to be that PVA isn't reliable enough compared to purpose made primers.

You should not prime a tile base unless specifically recommended by the adhesive manufacturer, the tile manufacturer or due to the tile substrate; highly absorbent substrates, plaster, plasterboard & some screeds must be primed with Acrylic/SBR primer when using cement powder addy. PVA affects tile adhesion (can be catastrophic if using large format tiles) & standard PVA remains water soluble so if you use it in a wet area & water gets through to the tile base, the PVA will re-emulsify & your tiles will fall onto the floor.

Can anyone suggest a suitable tool for scraping? My wallpaper scrapers/filling knives aren't strong enough and my screwdrivers are too small to get the job done this side of the London Olympics!

A flat bladed garden spade works well.

 

[tictic]

if its only a m2+
imo sbr/cement (slurry coat) over it.. the tile away with a rapidset flex

 

[roundthebend]

So, my local tile store may have given me poor info about using PVA to prime.

Yes & it’s well documented.

I've read a lot of debate about that but the majority vote seems to be that PVA isn't reliable enough compared to purpose made primers.

You should not prime a tile base unless specifically recommended by the adhesive manufacturer, the tile manufacturer or due to the tile substrate; highly absorbent substrates, plaster, plasterboard & some screeds must be primed with Acrylic/SBR primer when using cement powder addy. PVA affects tile adhesion (can be catastrophic if using large format tiles) & standard PVA remains water soluble so if you use it in a wet area & water gets through to the tile base, the PVA will re-emulsify & your tiles will fall onto the floor.

Can anyone suggest a suitable tool for scraping? My wallpaper scrapers/filling knives aren't strong enough and my screwdrivers are too small to get the job done this side of the London Olympics!

A flat bladed garden spade works well.

Great info, thanks.
I'll get the spade out this weekend - seems obvious now you mention it.

tictic - thanks for your opinion too. If I'm having little joy with the spade, I'll try what you suggest.

 

[roundthebend]

Right, the spade approach was useless in my situation. The layer of bitumen is so thin that the spade either glides over the top (too shallow attack) or just chips a line into the concrete (too steep attack).

I went back to the screwdriver approach which works but will take me weeks to complete.

Options now are to board over it - not not aquapanel thermal as it is too thick at 10mm and would leave an odd ridge between rooms.

Or, cement/SBR slurry.

The latter is my preference, so can someone suggest how to go about this? What materials do I need and how do I mix it and spread it? How thick etc?

 

[tictic]

dry lay your tiles first,get all your cuts done etc..

lift tiles..

1 part sbr mixed with 2 part cement (slurry coat),..pour it over surface,work it with a trowel over bitumen..

then when still wet/tacky...fix your tiles with addy..

job done.

 

[roundthebend]

Sounds good.
Where do I stand while laying the tiles? I'm getting visions of having to leave my DIY shoes in the middle of the cloakroom floor

 

[tictic]

Sounds good.
Where do I stand while laying the tiles? I'm getting visions of having to leave my DIY shoes in the middle of the cloakroom floor [/quote


you will only need to do m2 at a time,or depends how long your arms are..maybe more..as long as you dry lay at get your cuts proir to fixing.

and fix from far end off room,and work your way backwards..

so slurry coat area Xm2 then fix tiles,then other area slurry coat fix etc..

 

[roundthebend]

Thanks again tictic.
I think I've had a change of heart though as I don't trust myself with this slurry - I'll either mix it wrong, lay it badly, or make a complete mess of the rest of the house.

I heard about No More Ply which comes in a thinner board than the Aquapanel that I'd previously seen. I think I can live with the 6mm (or 7/8mm by the time I've glued it down) that it adds to my floor height.

The advantage being that I'll be more confident that I'm tiling onto a proper surface rather than just hoping. I'll also use the same boards for boxing in my pipework which means not having to buy lots of different materials.

I should be getting it overboarded this weekend ready for tiling during the evenings next week.