Subfloor prep over bitumin

[mattysupra]

Quote- Bellajules -
We have had to remove an old wooden floor which had concrete below it -which was coated by bitumen .In the concrete floor was some wooden batons .We have removed the wooden batons ,but we want to put down a new wooden floor.Is there any way we can screed over the bitumen?Or is there a damp proof product that can go over the bitumen -then we can put a screed over?

 

[mattysupra]

Your answer-
The subfloor SHOULD be shot blasted to remove all bitumen and glue residue.
But if all is sound and well stuck, you could prime with a neoprime primer and use a acrylic levelling compound. This will give you a good flat base. You can then use a epoxy dpm paint to deal with any moister problems. Now please remember that this is NOT a recommend method by the product manufacturer. You are relying on how well the bitumen paint is stuck to the subfloor!
The holes left in the subfloor by the batterns will need to be filled with a suitable repair mortar ect before any other work is carried out.
Do not use a latex flooring smoothing compound! These compounds are good for nothing and normally used by people who have no idea. ( 95% of builders ) They will stick to anything you put them over but have very little strength, so basically you can NOT use a epoxy compound or any sort of glue over the top!

 

[bellajules]

Thanks for the reply
We have been advised to use a tanking compound over the existing bitumen -without removal -Sovereign products
Then a latex screed on top


The other option was polythene and kingspan insulation -either float the oak floor on top of this or or use battons
The latter idea we did not like as you were nailing through the polythene -then the worry in case it sweats oak with the polythene
But we are worried about floating the floor -although the manufacturers instruction say that this is acceptable

 

[WoodYouLike]

Why would you worry about floating your floor? If your new wood floorboards are wider than 100mm and your underfloor/subfloor has been made sound I see no reason why you should not use the floating method.

 

[mattysupra]

Thanks for the reply
We have been advised to use a tanking compound over the existing bitumen -without removal -Sovereign products
Then a latex screed on top

Latex compounds should not be used if you plan to glue the flooring down. You can use under a floating floor tho! Really they should not be used at all. If you want to lay karndean, amtico ect in the future you will have to remove the latex to replace with the correct compound. You will damage your surface DPM doing this so you will have to do the whole thing all over again. I would advice acrylic based compound or water based.

As for using there tanking product over bitumen? Well if they say you can, then do it. Just make sure you get it in writing! I dont think i would use products off a company that advices using latex tho. But saying that it is possible to get a strong latex product but they do not flow at all and you will end up with a very uneven floor that will be of no use anyway.

But we are worried about floating the floor -although the manufacturers instruction say that this is acceptable

I cant see why you would not float the floor if the manufacturers say it is a recommended method? Alot of people dont like floating because of noise and the movement when they walk on the floor. Well this is only a problem if your subfloor is not flat and you use a cheap grade underlay.

Must say that i do prefer gluing the flooring to the subfloor myself tho. But this is personal preference.

 

[bellajules]

Thanks for the advice- the floor board are 83 mm,but it says we can float the floor -previous notes say this creates hinges???? help

 

[WoodYouLike]

Many short lengths create hinges, not long narrow boards - which if they are 83mm wide should not be floated!

 

[bellajules]

Thanks for the advice -however the manufacturers instructions say to float them -not nail them
What is the problem with floating narrow boards?

 

[mattysupra]

did they tell you to float them on a self adhesive underlay or pva the joints together?

 

[bellajules]

They told us to float the boads over a combilay and PVA the joints

 

[darren7]

I would love to see a picture of some of the peoples bitumen floor, as a lot of it is very slight residue, I have been told that as long as there is just a small amount of this, then gluing the floor would be ok, but the adhesive will take a little long to dry. true?


Darren

 

[mattysupra]

darren, who has told you that? This is not correct.
Many reasons why like the two glues react together, movement in glue in hot weather, moister been traped while setting ect . And what if the glue needs to sink into a surface to gain its strength? on bitumen it will sit on the surface!

 

[mattysupra]

They told us to float the boads over a combilay and PVA the joints

you have in writing then you may aswell do it.

 

[WoodYouLike]

I would love to see a picture of some of the peoples bitumen floor, as a lot of it is very slight residue, I have been told that as long as there is just a small amount of this, then gluing the floor would be ok, but the adhesive will take a little long to dry. true?

If only a little bit of bitumen residue is left on the wood blocks then glueing is ok - but the bonding with the adhesive will take longer indeed.

 

[darren7]

Interesting Matty, you are saying that a neoprime primer will stick.... whats the shot blast deal, do you hire or get someone to do this.


Darren