Ashlar pattern and expansion joints???

[firematt]

I'm preparing to cover my 3 year old concrete slab porch. It's 8' wide, covered and wraps around 3 sides of the house, which is 45' x 31'. I've picked out Silvergrey slate from American Slate Company. I'll be buying 16" tiles and cutting some of them to make an Ashlar pattern. They scored the concrete about every 8-10'. Some of the joints served their purpose and the concrete actually cracked in them. Then there are a few hairline cracks that aren't inside a joint. What will be the best (least visible/effective) way to deal with this problem? The Ashlar pattern has no long straight runs in it, and cutting the tiles at the joints would be unsightly. Any help is greatly appreciated, thanks!

note - The movement appears to be mainly horizontal.

[Davy]

Hi and welcome. I think I would put a membrane over the whole porch but still cut the tiles over the scores in the concrete. I would then caulk those joints with a color that matches the slate, not the grout.

[firematt]

Here is a link to Noble for CIS. They clearly show tile bridging over control joints and cracks. To me it seems that this method would work. What do you guys think? I know for a pro, a repair can cost you alot of money down the road. As a homeowner, a repair may mean that I spend an afternoon fixing a crack that has developed. A pain, but not alot of money.

My current plan is to use isolation membrane over the whole porch, and follow noble's guidelines, using a color matched sealant for the soft joints. I feel that this will be the most visually pleasing. If down the road cracks appear in the tile, I take out the cracked ones and replace, this time transferring the control joints directly through to the tile.

Any advice from those that have used the CIS from Noble for this sort of thing would be helpful. It seems alot of folk are recommending their products, so it stands to reason imho that the manufacturer's web site wouldn't steer me totally in the wrong direction. Thanks.