Finishing the underneath of a balcony

2 Apr 2008
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United Kingdom
Hi all,

I've recently moved into a house and some tidying up is needed. The house has a large balcony on the back, with a conservatory on it. Large space under the balcony is great for hanging washing, sitting in the evenings, doing "outdoor" work when it's raining, things like that.

The construction of the balcony is brick pillars with metal supports between them, and joists with some sort of wood flooring above, which is then tiled. It's mostly waterproof (i.e. rain runs off the edges rather than soaking down through it) but there are one or two small leaks - another issue for now.

The previous owner put rockwool insulation between the joists, from underneath, to insulate the floor of the conservatory. It's effective but unsightly.

I'd like to "make good" the underneath. Things to consider:
* "Ceiling" height is about 186cm, and I'm 183cm tall (plus shoes). Therefore whatever it is MUST be very thin.
* Balcony floor is not entirely waterproof (yet) and it's outside so covering must be suitable for that
* Something light-coloured would be nice, to make it look like a ceiling, not a dark box

Best I've come up with so far is some form of fabric stapled to the underneath. Best fabric I can think of is weed supressing membrane, because I know it won't rot outside, and it's porous enough for any water to escape. Problems are that it's black, and it'll sag a bit.

So, any suggestions please?

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Thanks for the reply.

Eternit seems to be the name of the company... which product of theirs did you use?

As for Trespa Mateon, how thick is that? Their website assures me it's wonderful but doesn't really tell me, erm, what it is or anything at all useful :) Also it mentions "vertical applications" but not horizontal... is it suitable for that?

Edit: Are you thinking I want to clad around the sides of the balcony? I want to make a "ceiling" on the under side of it. None of those claddings seems to meet the first two requirements (thin and water-permeable), only the one of being a nice colour :)

Yes I did read your post correctly that you wanted it for a soffit (ceiling). You fix them to the underside of the joists or battens with eithes S/S or coloured screws and would just leave the gaps between the sheets open without a gasket behind them, this is will allow your water to escape. Just as you would a timber or upvc soffit. As its a soffit you would uses slightly closer centres for the fixings to avoid it sagging when used as a soffit (like any product). The eternit boards are avaialable in 8 or 12mm thicknesses. You are not limited to leaving it in massive 8x4 sheets, you can cut it down to thinner strips or whatever. You can use any from the range on the link I posted last time just choose a finish/texture/colour that you like, I dare say the price will vary between the ranges. cladding part 1-1218.pdf Although the Natura range is the smooth one I recall and probably best suits your purposes.

Trespa is avaialable in 6,8,10 & 13mm thick again everything above applies here, they are (practically) identical products but different brands.

There are lots of downloads on each site with fixing guides, as you have observed the majority of cladding takes place on vertical surfaces which is why little website space is allocated to soffits.

Here's an extract from a soffit I did, you would do the same but without the gaskets. We used centres of 500mm for the fixings.
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Thanks very much. Roughly how much would any of these cost for about 20m2 please?

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