Question re: tiling (or using “thin” pavers) over concrete.
We have a painted 9×15 concrete slab in the back yard, as well as a small (3×7 w/steps) entryway that we’d like to cover over … w/stone tile, pavers, or anything else you might suggest.
The slab in the back is in decent shape – slight cracks, but overall holding up well … there’s 2×6 pressure treated wood bounding two sides of it. However, the paint job is peeling badly, and the slab is rather dirty. Not only that, but both surfaces (front and back) aren’t quite what you’d call level 😉
I’m mostly curious about what kind of prep work one needs to do on old concrete surfaces, prior to laying down mortar and tile/pavers.
I imagine at least cleaning w/a chemical compound, followed by leveling off w/some manner of self-leveling compound, at least?
Here’s one problem w/the cleaning, though – the slab is surrounded by new grass – after all the work we had to do to foster the grass, I’d *hate* to kill/harm it w/chemicals!
Any suggestions are much appreciated!
Replies
I can't believe the pros haven't responded to this, and I'm just a DIYer, so here goes.
I am guessing that a pressure washer will do a nice job cleaning off the concrete, as well as any loose paint. What ever doesn't come off is probably going to stay on.
There are different types of levelling compounds, and the packaging says which product to use for which application. If the store doesn't have all the types, try the mfr's website which would list all their product.
Depending on your climate (how much cold weather you get) you might want to install an isolation membrane over the slab, (under the tile), to try and mitigate tile cracking from freezing & thawing. I've only read about these, don't know how exactly to install. They sound pretty nifty. Again, the mfr should have installation instructions.
Tiles are also rated based on their hardness. I think the scale goes from 1 to 5. The higher the number, the tougher (read: less porous) the tile. For outdoor applications, you want a tile with a 5 rating. Be sure and use exterior graded thinset & grout.
And finally, from what I've read, most colder climate professionals recommend AGAINST installing tile outdoors for all of the above requirements. Tiles will pop off and/or crack regularly, grout will do the same (water penetrations, freezing & expanding, etc).
That's all the stuff I can think of. Good luck.
Theresa
A good, not-too-toxic way to get good adhesion on old concrete is to bush hammer the old surface to expose fresh concrete, after you've pressure washed it. A bush hammer is a bit for a breaker(jack hammer), looks like a meat tenderizer. No chemicals neccessary, just some noisy elbow grease and a bit of dust.
Depending on how not quite level 'not quite level' is, you can skim coat it with thinset mortar and even it out a bit (this will get you 3/4 of and inch or so) More than that and you may need to pour another inch or inch and a half of concrete and shoot some mesh or heavy stucco wire to the old surface.
Exterior tiles must be vitrious, ie do not absorb water. This is what causes cracking, when the absorbed water freezes and expands. You should be able to get some kind of paver that will stand up, although it may not be ceramic ie concrete or stone. Porcelain tile will stand up but is expensive. Perhaps a tile border with less expensive paver.
Of you are in a really cold zone, like Manitoba or Minnesota, and are paranoid about tile cracking, stick to stone or consider options like pouring a coat of colored concrete or staining concrete. You can get some great effects with stampcrete, when you impress a pattern into wet 'crete.
Consider removing the pressure treated and tiling the sides.
Good luck