sick of bitumen - decisive help needed.

[mrsmeagher]

Hi DIYnot.

We are in the final throws of completing the rennovation of our house. I am an accountant but my husband is the contracts manager of a building company that does insurance work. But we are totally sick of trying to find an answer for the following.

In summary:
We have a solid concrete based conservatory, it has a dpm just under the surface and due to historic damp we primed the base with a bitumen paint (roofing paint) primer and then 2 coats of bitumen roof paint. The product is Marley Universal Bitumen Waterproofing Paint. In total the primer and paint is barely 2mm thick.

We are going to instal an electric heating mat onto this base with a natural stone tile over the very top. Because of the size of tiles and bumpy surface we need to put a levelling compound over the top of the mat but all we hear is "it won't adhere to the bitumen".

I need an answer PLEASE, someone!!!! -

We don't want to use a latex compound as we have been advised this is too flexible and won't adhere. We understand an acrylic compound is that we need but then other people say no. - HELP!

I have even considered just sticking hardboard down to the bitumen with a construction adhesive and then putting the heating and compound over the top.

Please can someone give me a solution.???

Many thanks, a very very stressed Hayley

 

[Hugh Jaleak]

Might be wrong, but a layer of polystyrene (for insulation), then UFH, screed over to level, then tile.

 

[mrsmeagher]

hiya - I haven't heard that suggestion before, how thick polystyrene? Also will this be solid enough to support the natural travetine tile, because we have been told that any give in it and it could cause the tiles to break or crack.

thanks x

 

[ivixor]

How bumpy is bumpy? If its the kind of bumps that a floor leveling compound is meant to remove, surely a 5mm notched tile adhesive troweling will sort it out? Bed tiles into adhesive with spirit level, job done?

 

[alittlerespect]

Hi

Depending on how much height you have to play with you could go for a knauf earthwool thermal floor slab laid directly onto the existing oversite, lay tongue and groove flooring grade chipboard over the top - glue all tongues as you go. [you may wish to pack the perimeter edge with some thin insulation material no more than say 12mm thick polystyrene is an ideal candidate for this job as it is easy to cut but a little messy, this will assist in avoiding thermal bridging between the wall and the floor] and then lay your tiles directly onto the chipboard with a tiling adhesive.

What you do with the electric heating mat is up to you, personally I would leave it out as its going to cause more problems than it solves - all ok in a perfect world, which its not!

One final comment - the end solution really depends on what you are trying to acheive and how much height you have to play with between the floor and the door threshold, the above proposal would add 25mm (insul)+ 18 mm (t&g) + say 12mm (tiles) = 55mm ideally you would want a minimum of 50mm insulation which would push the thickness up to 80mm.

Food for thought!
Regards

 

[mrsmeagher]

hiya, thanks for your responses so quickly

We can't leave out the heating mat as the room is acting as my office and the floor is sooo very cold that we need it just to take the chill off.

We want to do the least about of layers as possible and arn't really fussed about putting insulation under the heating mat.

Basically we just need a self levelling compound that will adhere to this bitumen paint. From what i have read people say that these compounds won't adhere to bitumen but it sounds like many people are talking about a very thick covering of bitumen where as this is just about 2m

Our tiler has told us that to lay the natural stone tiles 600mx 300m they involve alot of working the adhesive which can risk ruining the heating mat so it needs to be put in a leveling screed first.

Does anyone know a levelling compound that will stick to this bitumen paint? or because it is so thin do i not need to worry?

 

[hotrod]

2 options mrs meagher:-

1. If you can bed straight onto the bitumen/mat use Ardex X7 to fix tiles.
2. Prime substrate with Ardex P82 then use Ardex K* self leveller prior to tilling.

Contact Ardex for more info:-
http://www.ardex.co.uk/contactsindex.asp

*Other self levellers and tile adhesives are available*

hth

 

[mointainwalker]

No insulation under heating-mat = more than 50% of heat wasted by going into the ground.

how many m2 is your conservatory ?

 

[mrsmeagher]

thanks people all these suggestions are great - I will look into that Ardex.

My conservatory is only 10 square metres but is quite a significant proportion of downstairs as my house is a new build so is rather tight.

I will look into insulation below but we don't really want to build it up too far and it needs to be very solid as not to provide any flex for the natural stone on the top

Thanks for your input everyone , its really helpful

 

[foxhole]

Can't heat a conservatory with electrical under floor heating, just can't cope.
Heat in a conservatory goes straight out thru the roof which is very thin so unless you stick a couple of rads in there you will shiver.

 

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