Tiles on pedestals - any good?

[lookseehear]

We're weighing up options for our roof terrace. We initially assumed we'd use timber decking but there's no way I can be bothered to clean and re-treat/paint every year, so durability must win out. We then moved to the idea of hardwood (Ipe) decking tiles, but given we don't have a lot of thickness to work with I'm now leaning towards tiles (porcelain maybe?) on pedestals. I like how quickly they go down and how easy they are to remove if it's ever required. This will be going on top of a warm roof with EPDM, so my concern is the pedestals damaging the membrane.

 

Has anyone ever used them? Do the tiles feel and sound solid on top of the pedestals or do they just sound hollow and feel wobbly? Any issues using them over EPDM?

[nod]

As a business I used quite a lot of these we normally put a blob of resin on the bottom of each pedestal No harm to the covering Very quick to go down We normally do a 30m2 balcony (roof) in a day 20-25 mil Porcelain Indestructible

and you say You can easily remove them for cleaning or unblocking drain

Just lift off 

[lookseehear]

On 03/10/2024 at 18:13, nod said:

As a business I used quite a lot of these we normally put a blob of resin on the bottom of each pedestal No harm to the covering Very quick to go down We normally do a 30m2 balcony (roof) in a day 20-25 mil Porcelain Indestructible

and you say You can easily remove them for cleaning or unblocking drain

Just lift off 

 

I'm coming back to this and my worry at the moment is about how compression resistant PIR is. I assume I can't have PIR, with single ply over, with pedestals straight on top? Would I need an intermediate layer to support the load of the tiles plus people/furniture so as not to damage the insulation through compression (like another layer of OSB or ply)?

 

A bit of research has shown me that you should ideally have 300kPa/m2 underneath the pedestals, but PIR appears to be in the 120-150kPa/m2 range.

 

Edit - would adding a thin layer of XPS over the PIR allow me to get the load-spreading required? XPS seems to be in the 200 kPa range and higher.

Edited October 30 by lookseehear

[Nickfromwales]

How many layers of ply are under the membrane? 1 layer of 18mm OSB3?

When you factor in the weight dispersion of the pedestal sitting on top of that it already behinds to spread the issue out, vs you considering it direct to the PIR. 
You could also make some plates for the pedestals to sit on, maybe 300x300 porcelain, and that’ll prob suffice.

 

Talk it through with manufacturers and suppliers reps to see what does/doesn’t work, and what been reported to have failed over time, which is for you to do for your own diligence, is the correct advice obvs. 

[lookseehear]

I've emailed a couple of businesses selling tiles and pedestals, as well as asking kingspan what they would recommend. Kingspan suggested I talk to a structural engineer, one other business said 18mm osb would be fine and another hasn't got back to me.

 

Ideally I'd lay single ply membrane directly onto PIR, then pedestals directly onto the membrane, but my suspicion is that an 18mm layer of osb under the single ply membrane would suffice.