Use a decoupling membrane. Also, be sure to check that the slate is suitable for outdoor use. In a temperate or colder environment, the freeze thaw cycles create havoc with many if not most slates. I personally prefer porcelain.

Thanks, worthy!

Slate/concrete will surely be heavy. Make sure your supports are/will be sound to hold it up.

Thanks -- Basically what we're trying to decide is whether to have support piers (ie, for a decked porch) or a full foundation (for a concrete porch). We like both aesthetically, but I want something that will hold up well.

chompskyd,

Another thing to consider, if the porch is above ground 30" and decked, were you thinking to leave it open around the ends or enclose it? What will you put under it - rock or woodchips? It may be difficult to gain access to get out the leaves, debris, etc. that inevitably gather under open spaces (speaking from experience).

On our new home our entry porch and 10x26 covered porch are poured concrete slabs. We broomed the finish to start so it isn't slippery and can at some point tile the porch floors or do a stain treatment, but do like them the way they are. We haven't had any cracks show up yet and it's been a year, including a cold winter. I think the concrete will hold up looking good and with less maintenance than decking over the long run.

Jill

We had the builder reinforce under the porch and had the concrete poured 2 inches below the brick foundation.
My husband and I added stone to the porch. We had picked out the stone ahead of time and knew it was 2 inches thick.
{{gwi:1446861}}

My preference would be a slab with a decoupling membrane. If the porch will be open to the elements it is a good idea to put some slope on surface to drain water away from the building.

Thanks, all, for your comments. lsst, your porch is lovely.

I agree with blindstar/worthy. CMU permiter, tamped fill, 6" gravel, 4" concrete slab, decoupling membrane, slate tile. Instinct would say that if the porch is poured correctly it would outlast a deck but with current advances in decking products I'm not so sure. Seems like a push to me.