Insulation over Terrace

R

Ruam

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We are currently building an extention and over the kitchen dining area is a flat roof which we are using as a terrace (5m X 4.6m) accessed from the first floor bedroom.

We have a poured concrete roof and under the concrete 1.75 inches of rockwool insulation. There was a mixup with the builder, I wanted 50mm kingspan insulation which has a much higher insulation value but the job has already been done and the ceiling slabbed.

I'm concerned that there is not enough insulation as the rest of the house is very well insulated. Is there any way I could insulate on top of the concrete, keeping in mind that we are using it a terrace? or would this be a waste of time and money?

Any advice?

Ruam
 
Hi Ruam. I presume that you are putting some sort of water proof membrane on top of the concrete. I have a similar set up and I used 50mm kingpan on top of the concrete before applying a rubberised membane and then paviours on spacers. Obviously it would be preferable to have as much insulation in the ceiling as possible as insulating on the outside means your heat is also getting in to the concrete pour.
 

Ted,

Thanks for that. Yes there will be a water proof membrane on top of the concrete.

Do you know if the insulation on top of the concrete makes much difference?

What did you put on top of the insulation so as you could walk on it?

Ruam
 
I have seen gravel over foam blocks used on the roof. Might not be the best solution if you are using it as a terrace. Maybe wooden decking over the gravel. Sounds messy and I would hate to get a leak.

Towger.
 
You can use insulation over roof membrane on concrete deck- this is technically an "upside down roof", where the roof membrane is effectively a vapour barrier and the insulation will protect the membrane below from thermal movement and UV degradation. The concrete acts as a thermal buffer, storing up some heat during winter and keeping the room cooler during summer. BASF do a suitable product which can be used in this way, with a wearing surface of gravel, paving or decking added. This product is very expensive. If you opt to insulate under the roof membrane Kingspan, Moy Materials and others will have a suitable product. If you opt to put paving or other finishes on top of the deck be sure that the structure is designed for the additional dead load. The answer to your question is that all is possible...
 
Ruam said:
What did you put on top of the insulation so as you could walk on it?

Ruam
Click to expand...

I put a fleece, bearing pads and paviours. Your membrane supplier will recommend a suitable bearing pad. Briggs Roofing and Cladding in Cork supplied the fleece and bearing pads for me. It's not expensive and relatively easily installed. The fleece and pads should cost approx. 300E for the area you're talking about. The water then runs off under the paviours. My advice is to go for the largest concrete paviour available being mindful of also choosing one to suit your overall dimensions. I used a 600mm x 600mm paviour - in your case that would be about 8 x 7 = 56 paviours allowing for space between them. The larger paviour is heavy and doesn't lift as you walk on it.
 

Ted,

Thanks for that information. Any idea what it would cost to put 50mm kingspan and then fleece, bearing pads and paviors on a 5m X 4.6M area? A rough ballpark figure.

Ruam
 
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