Sandstone porch

[geraldthehamster]

I have a large quantity of sandstone that was once part of a Victorian church. For transportation it was cut into irregular blocks a cubic foot upwards in size.

I'm thinking of using some of it to build a front porch. To stay within PD it will need not to exceed 3 square metres, externally- or a semi-circle of 4' 6" diameter. It will continue an existing porch that is set back within the external wall by some 4 feet, so insufficient length isn't a problem.

However, the sandstone will rob at least a foot from the internal dimensions on each side (ie it will be a max. of 2' 6" inside), so in order to turn round in it, I think I'll need to make it of sandstone alone - ie no inner skin of any kind.

Which brings me to my question: does the team think that rain will penetrate the stone and make the porch unpleasantly damp, especially in winter?

Supplementary question - should I use lime mortar, to avoid the appearance in a few years time of an interesting cement lattice with a lot of stone-shaped holes in it?

Cheers Richard

[newshound]

Sandstone should be pretty impervious to water, shouldn't it?

To avoid condensation, you either need ventilation, or have it well sealed with some background heating.

[Tabby]

9" solid walls are fine damp wise, especially with a dpc. Yes the walls can get a little damp, but not normally enough to cause any problem. (There's a big difference between damp, which is normal in any wall to some extent, and a damp problem.)

Yes. It takes a long time for that to happen, its really when the cement finally lets go after decades that it can go wrong. You can get away with adding 5% cement to the lime mix so it sets fast enough to not delay building.

NT

[dom]

I think it depends on your sandstone. But around here, North Norfolk, those free-standing cement lattices are all too common, where someone has unwisely repointed in cement.