Construction type

[CraigCTH]

Hi building a single storey new build into a bank side roof is going to be a grass roof , do we go for traditional build with a concrete roof or what are other alternative methods thanks in advance

[MikeSharp01]

You can make any construction type deliver a grass roof so it comes down to preference, usage and cost. Do you want to graze your elephants on the roof or is it just ornamental and taking no more load than the grass + snow?

[CraigCTH]

Grass and snow but the thing is the roof is at ground level with earth banked up round the sides, it's getting a substantial roof to stop rabbits, rats what ever burrowing into the roof and also we don't want load bearing pillars ruining the open plan layout

Edited August 5, 2017 by CraigCTH

[Jeremy Harris]

What sort of span are you looking at?

 

If the span is going to be quite wide, with no intermediate supports, then you'll be looking at either steel of concrete beams. 

 

You also need to decide where the insulation layer is going to go.  For a partially earth sheltered structure it's often better to put the insulation on the outside, and because of the need to reduce/eliminate thermal bridging, this means having the same insulation configuration on the walls and roof, and ideally the floor, too.  The alternative is to fit all the insulation on the inside, which may be simpler to do in terms of ensuring that thermal bridging is minimised.

 

I've not heard of pest problems with green roof structures, and they often just use a butyl membrane as the waterproofing, under the soil layer.  The depth of soil isn't usually deep enough for rabbits to be a problem, and rats only stay around wherever there is a food source; they don't normally choose to live anywhere where they can't get a free meal.

 

 

[Mr Punter]

The back wall could be concrete, blockwork, ICF or steel. You need an engineer to design this.  You need to carefully consider waterproofing and insulation, as well as structure.  Discuss your proposals early on with your warranty provider.

[Jons]

As far as the roof cover is concerned I shouldn't worry about rabbits/rats etc. We have an old water tank with an earth cover and there has never been sign of them being interested despite rabbits in the field and rats near the adjacent stream. I don't think the earth is deep enough to be hospitable - also when you are living in the building there will be too much disturbance/noise for them to want to hang around!

[mvincentd]

I've got 97 x 373 posijoists at 400 centres clear spanning 6.7m to support a 'biodiverse' flat green roof which is at ground level with earth banked up around the sides.  This is still only sufficient to rate it as a roof as opposed to a full-on amenity space to hold a rave on. (rave...do they still have those?)