EDPM and tile pedestals for flat roof terrace

[Adam2]

I'm going to have a couple of roof terraces that are over habitable rooms and currently expecting to use EDPM with the structure beneath being waterproof concrete. The finished surface will be tiles on adjustable pedestals.  So am thinking the make up will be:

 

concrete -> VCL -> PIR -> EDPM -> Pedestals -> tiles

 

Should the VCL be beneath the concrete instead?

 

I'm guessing I should probably have OSB or similar attached through the PIR (below EDPM) into the concrete to ensure rigidity? 

 

Should I expect wide based pedestals to spread load sufficiently such that they would not damage the EDPM or PIR?

 

 

[scottishjohn]

seems a long way for a short cut

If  roof strcuture is concrete -why would you need any other sort of layer 

just tile it with exterior quality floor tiles and exterior type tile adhesive ( frost proof)--job done

[Adam2]

Hi - well, we'll be needing the insulation over the concrete (AFAIK) and will be laid to a 1:40 fall so will be using the pedestals to level out the tiles (free-draining where the grout would usually be). BUT - please, if there are other ways to achieve this then totally open to hearing about them. I don't really want the insulation inside as that will impact the ceiling heights/cause various dramas with levels etc.

[Russell griffiths]

I have no experience with this, but my thoughts after doing icf pours would be 

I would expect the concrete to be air proof so I cannot see what a vapour check on the inside would achieve 

 

[Ferdinand]

I am on my third mini project with these (disabled ramp, which is techncially not quite their intended use)  now use only ASP Wallbarn as they are very good with discussing issues, sending samples etc. Worth a conversation.

 

F

Edited October 1, 2019 by Ferdinand

[Adam2]

Thanks. Will look at those pedestals also.

Agree re VCL over concrete all good there.

 

My questions in initial post were in relation to whether I need OSB over the PIR and beneath the single ply and if I also may need something over the single-ply as this will have pedestals and tiles on top of it? 

 

Would be good to know what others have done and how it has worked out.

 

[Ferdinand]

12 hours ago, Adam2 said:

 

Should I expect wide based pedestals to spread load sufficiently such that they would not damage the EDPM or PIR?

 

 

 

I think is one for professional advice from the tech support people at the manufacturer.

[Pocster]

Though my walk on / drive on roof is more complex I couldn’t penetrate the water proof layer but needed to have a layer to protect my vacuum insulation . I used a t & g type cement board . This gave stability and protected the insulation. I did also have more concrete ontop as well ! 

[mvincentd]

A possible alternative might be westwood-uk.com  ,they're in Poole.

Subject to you're being ok with the aesthetic I think they could potentially achieve in one thin product what your edpm, pedestals & tiles do.....notwithstanding leaving you with the 1:40, which depending on your use of these terraces may/not be an issue.

[Adam2]

Thanks for the link - but we're looking more for a tiled look to continue the inside outside  or the outside inside whatever it is :-)

[willbish]

I'm not familiar with the compressive limits of PIR but here is XPS with pedestals on top without a plywood layer.

 

This detail may also be of use, which I am broadly following.

 

 

[mvincentd]

20 hours ago, Adam2 said:

but we're looking more for a tiled look to continue the inside outside

Sure...it is limited aesthetically, though they can achieve 'tile effect' ( https://www.westwood-uk.com/news/balcony/full-pmma-waterproofing-system-with-fantastic-tile-effect.html ), but wouldn't really be able to convincingly match an interior tile.

[Adam2]

Cheers @willbish that detail is really helpful - plenty of interesting products from IKO!

[Mr Punter]

I am not keen on the inverted roof with the waterproofing under the insulation as the insulation can be compromised by water under it.  I prefer a layer of OSB or cement board over the insulation to carry the EPDM.

[mvincentd]

2 hours ago, Mr Punter said:

I am not keen on the inverted roof with the waterproofing under the insulation as the insulation can be compromised by water under it.

And I believe you have to go from pir to xps in order to use this method due to being 'in water'....so thickness for equivalent u-value increases significantly.

[Pocster]

2 minutes ago, mvincentd said:

And I believe you have to go from pir to xps in order to use this method due to being 'in water'....so thickness for equivalent u-value increases significantly.

Or ! Vacuum insulation. Much much thinner for same u . But much more expensive...

[scottishjohn]

On 30/09/2019 at 22:13, Adam2 said:

Hi - well, we'll be needing the insulation over the concrete (AFAIK) and will be laid to a 1:40 fall so will be using the pedestals to level out the tiles (free-draining where the grout would usually be). BUT - please, if there are other ways to achieve this then totally open to hearing about them. I don't really want the insulation inside as that will impact the ceiling heights/cause various dramas with levels etc.

too late now

but maybe you should have laid insulation and cast  concrete  roof on top of it ?

 suppose you could fit insulation and then  cement board  or a 2" cement screed and then tile  on that that  and drianage from above that 

I could be wrong but seems very complicated with pedestals and a wet sump area around your insulation --which could freeze in winter  and no plywood in the construction anywhere --thats just a booby trap waiting to rot away 

 

Edited October 3, 2019 by scottishjohn

[Adam2]

22 hours ago, scottishjohn said:

too late now

Ahh - nothing is too late - this is still at design stage - my concern re changing construction method significantly and impacting levels etc was going back to architect & SE, which I can do of course if that is the right thing.

 

 

Not sure of the booby trap/rotting? I though the make up was a pretty standard approach and similar things must have been done recently many many times for roof terraces etc. The questions really were just around the pedestals on the EDPM on the Insulation and whether this may pose a problem with durability of the EDPM - have since seen the pedestal makers state they are for installing direct on the EDPM so this should be OK  : https://www.rubber4roofs.co.uk/shop/paving-slab-support

 

[scottishjohn]

2 hours ago, Adam2 said:

Ahh - nothing is too late - this is still at design stage - my concern re changing construction method significantly and impacting levels etc was going back to architect & SE, which I can do of course if that is the right thing.

 

 

Not sure of the booby trap/rotting? I though the make up was a pretty standard approach and similar things must have been done recently many many times for roof terraces etc. The questions really were just around the pedestals on the EDPM on the Insulation and whether this may pose a problem with durability of the EDPM - have since seen the pedestal makers state they are for installing direct on the EDPM so this should be OK  : https://www.rubber4roofs.co.uk/shop/paving-slab-support

 

there are a few systems that use insulation as the roof to then pour your concrete on to 

     https://www.insuldeck.com/           thats first one i found --lots of others.