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installing Slate title to outdoor cement

65K views 53 replies 9 participants last post by  Bud Cline 
#1 · (Edited)
installing Slate tile over outdoor concrete patio

I've been assigned a outdoor project from my wife. It is very important that I do this right or my wife will be mad at me. We don't want that!

I have a 20' x 20' outdoor cement slab that I plan on covering with 12" x 12" slate tile. 16' x 16' of the patio is covered with a patio cover, stays dry year round

Here are my thoughts, let me know what you think.

1: use masonry cement to install, the slate tile to the cement slab.

2: use the masonry cement as a grout.

3: eliminate the need of a masonry grout and butt the tiles together.

4: install the tiles over the cement using sand. Paver method and lock the outer edge titles with masonry cement to keep the slate from shifting.

I don't know of an outdoor grout. I have only seen masonry cement used like a grout. I am concern about staining the slate with the masonry cement. I do plan on treating the surface of the slate prior to installing.

Let me know your thoughts or direct me how to do this project correctly. Of course the cement patio is not flat. That's why we selected slate tiles so the flatness is not a big concern.

Thanks for your time. Remember you will be saving my marriage by providing solid advice.
 
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#2 ·
if you have any freeze/thaw, the wife'll be upset when your work comes OFF the patio,,, other'n that, just about everything you propose won't work. concrete not being flat, makes no difference what mtl you select,,, it still won't be flat UNLESS you do it right.

marriage counseling's another forum altogether :censored:
 
#4 ·
Obviously you haven't bothered to research anything and you just want personalized express help with this.:)

OK, here ya go....

1: use masonry cement to install, the slate tile to the cement slab.
Not on a bet! Use the proper modified thinset mortar suitable for exterior use.

2: use the masonry cement as a grout.
That's do-able, but use sand mix not masonry cement, you don't want the lime in there it will likely cause efflorescence.

3: eliminate the need of a masonry grout and butt the tiles together.
That wouldn't be smart. That would allow for water to get deep into the project and it wouldn't last the first winter.


4: install the tiles over the cement using sand. Paver method and lock the outer edge titles with masonry cement to keep the slate from shifting.
You must be spending too much time in the sun!:) That wouldn't make it through the first rainfall using slate tile. Pavers maybe but tile? NO WAY!:)




I don't know of an outdoor grout.
Any Portland cement grout is an "outdoor grout".

I am concern about staining the slate with the masonry cement. I do plan on treating the surface of the slate prior to installing.
As you should be. Install the slate, seal it a couple of times, grout it, seal again.


Thanks for your time. Remember you will be saving my marriage by providing solid advice.
With some of those ideas it's a wonder she hasn't divorced you already. The above recommendations will save your marriage.:)

Bud Cline -
Marriage Counselor
 
#5 ·
Thanks Bud for the advice and saving my marriage. Actually, I did a bit of research and received multiple ideas, from places that sell slate tile. This is why I posted here. That is the problem with contractors today. If you don't know better they will do the job wrong and latter say, it not my fault you approved the work!
 
#6 ·
I have several outdoor slate patios and walks in the state of Nebraska and brother if you don't get freeze/thaw here you don't get it anywhere.:)

If you have access to Mapei products I would recommend you use Mapei's KeraBond and mix it with their Keralastic additive. This will produce a better mix than what you will get buying an already modified thinset.

If you can't find Mapei I can put you onto something else.

If you have Menard's they sell Mapei products.

 
#8 ·
The customer provided the slate. It's that stuff from Home Depot of course, they love it. I have a bunch of it inside the home also.

Did two fireplaces (one stone, one silver slate) for them a few years ago and a bathroom in porcelain.

They were warned about the shedding using it outdoors and that doesn't bother them. It easily survived last winter and nothing shed, it was snow and ice covered several times. That slate has about six coats of that $100/gal stone sealer on it. We'll see what next winter brings.

The front of the house is on a park with a lake. The compass rose points to magnetic north just for fun. The maple leaf is just a wild hair I had because of all the trees around. There is also a hummingbird and a butterfly there somewhere.

I always disclaim slate indoors or outdoors. No way I'll stand behind it. Slate sheds, that's all there is to it. It's a bigger problem in a shower where it can leach iron oxide forever, also not my problem. This patio shows signs of leaching but personally I think it is an enhancement.:)

 
#9 ·
I think Bud said something that some might overlook seeing the cool pictures and all: he said "I always disclaim slate indoors or outdoors"...ah! true words indeed!

Now, why do you think a pro installer like Bud in Nebraska would say that? after all, according to those pictures, wouldn't you think he knows what he's doing! Wouldn't you wonder why? I don't...

Matky, I'll just add my 2cents worth to what Bud and yesitsconcrete have already intimated: there are problems with slate outdoors and in my relatively limited experience, I haven't found one yet that has proven - in time - acceptable to the homeowner, and in spite of the number and kind of sealers they put down. So, that tells me that there's something fundamentally wrong with the use of slate, because each of the installations I have witnessed used proper - yet different, albeit similar methods. What I mean by that is that each one was outdoors, each one was a slate, each one was on concrete slab, each one had an antifracture membrane - but each one used one or two different sealers with different exposures, different costs of slate etc. (Personally, I liked the Vermont slate the best).

I've come to the conclusion that the slate was the problem. Spalling, or delamination, and streaking of calcium salts, were the result - and that comes down, IMO, to what slate actually is as a "stone". It's laminated mud that contains a number of different minerals. Note I didn't say any words like calcairous, rock, metamorphic or stone...just "laminated mud"...

Muds originate in water and can revert back to water if prodded. So slate can delaminate, IMO. Some more or sooner than others but that's just the nature of layers of mud piling on top of each other. Add to that the minerals that can react with water and cause further problems and you have a short receipe for disaster. And slate roof tiles? Sure! they're fine up there - but not on a slab!

So what can I say to you? Here's what: in order to save future grief in your marriage, let your wife know all this so that when it fails, you can say: well, we were warned, weren't we? What that'll do is shift the blame from you to us - and we can take it. :laughing:
I have always been at my persuasive best when asked to do a slate shower or outdoor installation and fortunately to date my reputation is intact. I've done more than I want to of that type of installation and where I left my signature behind, there is a strongly worded disclaimer, like Bud's I guess.

So, go ahead, do the installation - once you've taken the advice that's posted in this thread, but then add the advice I gave you above.

You'll thank us all down the road.:huh:
 
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#11 ·
i don't think slate's bad if its used correctly - just the cheap **** that's being imported, 'specially from india,,, we used slate for yrs beginning in colonial times for headstones - largely because it was easily available & the cutter could use steel tools to shape/carve/engrave it.

mainly in the last 50 yrs its started to delam,,, after all, it is still mud compressed to stone by eons of pressure.

my bride recently informed me she wants granite c-tops,,, yikes !!! most of the stuff avail today's imported junk but its cheap, flashy, & in vogue,,, personally i like slate or soapstone,,, however, she's the 1 who must be obey'd :whistling2:

slate's a 100yr roof & well worth the $$$ but its being challenged by conc tiles today very successfully.
 
#12 ·
That's my point yesitsconcrete: I have done correct installations but the slate still gave problems. And I agree: the cheap slate they bring in from overseas is just that: cheap slate. I just haven't found a good slate yet, I've seen good slate and bads slate, no great slates. Had I found a great slate I wouldn't hesitate in using it and recommending it.

And same thing with "granite"...all the stuff they import as basalt becomes granite when it reaches North American shores...there is no classification and thus the opportunities are there to charge high prices for junk. There are only about two dozen stones that have the right to be called 'granite' and you and I may not see any one of those any time soon. But a lot look like granite, feel like granite and behave like granite so I guess it's granite.

Who am I to argue...:whistling2:
 
#13 ·
finding good cheap slate's like finding a good cheap tool :laughing: either with OR without ' legs ',,, pen argyl, vt, & va produce some good mtls but its tough to get what they have to have to cover costs, pay ovhd, & provide a profit,,, here, ga marble's been bought by the french for crushed mtls - ONLY ! ! !

spend 20 yrs in the monument trade so have some ideas what good granite is,,, today's stuff, for the most part, is ****,,, we're on the same page, bud :whistling2:
 
#14 ·
As long as there's a market for crap people will buy crap, they don't know any better anyway. That Chinese slate shown above is OK for what it was used for. I kind of like the look and to tell you the truth it's easy to work with 'cause there's nothing you can do to make it look any better than it does coming out of the box.

Is it crooked?
Damned right it is!

Will you have lippage?
Damned right you will!

Will it delaminate?
Damned right it will!

Will I warrant any aspect of the installation?
Damn right I won't.:)

I read an article somewhere not too long ago that said Vermont Slate was one of the most reliable consistent slates being quarried anywhere in the world. I think colors are limited tho.:)
 
#16 ·
Is your keyboard missing some keys or what?:)

Let's see if I got this right.

i think pen argyl's probably the best
OK, does that have something to do with Pennsylvania?

What is "argyl's"?


vt gives up a green
....and that has something to do with Vermont?

va's slate's dark grey/black
Now we're talking about Virginia, is that correct?

Man those posts are hard to read and understand.:)
 
#18 ·
My husband and I have dark gray slate chalkboard from an old school. We cut and installed 12x12" tiles in our entry way and I'm was curious about doing the same on our front stoop outside. The area is roughly 4x6' and we live in in the midwest where we get lots of cold weather. So my question is would this be a viable option for over our cement slab entry way with thinset or Mapei adhesive. I read all of the posts and I'm not sure - maybe this slate will be better than the new imported. It's got one side smooth and one side slate textured that was glued to the classroom wall. We like to recycle!

Thanks!
Amy
 
#19 ·
Well, sure you can!...I don't think anyone has ever said you can't put slate in any place in your home, including bathroom shower stall or kjitchen countertops - it's just that some have seen examples where it was not suitable that makes them suggest something else. In this case, you've recylced a blackboard...well great! saves it from the rubbish heap....

Inside I don't see any problem but outside you may see some problems down the line. But who am I to say "it wasn't worth the cost" or "you paid too much" or whatever. But bear in mind that slate sometimes delaminates under water pressure, so protect the bottom and protect the top and see how long it lasts. It may last beyond the point where you still "like" it and figure it's a time for a change anyways. In that case, you're well ahead of the game! :wink:
 
#20 ·
First, I want to thank Bud, Concrete and Carlyle for your comments. I WAS about to put down some (cheap) slate (from Lowe's) and was looking on this forum for a few answers. I will now go to the tile store and maybe get "good" slate, or go ceramic, or whatever you recommend. You guys obviously know your stuff! But, I still have the same the question I started out with, and I hope you guys can help me.

I'm putting down this tile (whatever I end up with) on my covered front porch 5' x 16'. I just spent ALL DAY anlge grinding it to get the 12 layers of paint off it and my back is killing me. The porch is made up of two slabs. So, in the middle I have a gap of about 5/8 inch with an expansion joint that is only half there and the other half has rotted away. (I'm going to try to add a photo).

Question 1 - How do I prepare that gap? Do I fill it with cement and tile over it, or what? Will that work?
Question 2 - Once that gap is prepared, am I ready to lay the tile, or is there some other prep that is required.
Question 3 - Since the porch is covered, and doesnt get much moisture, would the slate be ok?
Question 4 - What "slate looking" alternative would you recommend instead?

Thanks for any responses!
Steve
 

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#21 ·
Question 1 - How do I prepare that gap? Do I fill it with cement and tile over it, or what? Will that work?
Under no circumstances do you want to tile over that gap. That expansion joint must be honored all the way through the tiles surface. Clean out the gap and then either fill it with an exterior caulk or some foam backer rod then caulk. The joint must be able to move with climatic changes.

The tile should have a grout joint at that location also. Only, don't use grout in that joint, use a grout-matching exterior caulk there also. The joint must remain flexible. There are also ready-made expansion joints available if you are interested in one of those.

Question 2 - Once that gap is prepared, am I ready to lay the tile, or is there some other prep that is required.
You could lay tile at that point if your remaining slab isn't showing any cracks. There are also ready-made isolation membranes available if you so choose.

Question 3 - Since the porch is covered, and doesn't get much moisture, would the slate be ok?
Slate is always iffy out doors in a freeze/thaw climate.

Question 4 - What "slate looking" alternative would you recommend instead?
There are many porcelain tiles that mimic slate. Look around, most of them are fantastic and some have a "high-relief" that shows strong cleaves.
 
#22 · (Edited)
Thanks for the reply, and excellent advice! Now, one really stupid question.... the joint for the tiles, sitting above the expansion joint...can the tile joint be 1/4 inch, or does it have to be the 5/8 to mirror the exansion joints width? I know, stupid question...but I'd believe either answer!

Oh yeah, one more question:

When I lay the vertical tiles, which will be touching the dirt (and therefor subject to lots of moisture, is there anything I should do, other than just laying the tile in?

Thanks again... and especially for the amazingly fast response!
 
#23 ·
...question.... the joint for the tiles, sitting above the expansion joint...can the tile joint be 1/4 inch, or does it have to be the 5/8 to mirror the expansion joints width?
The joint in the tile can be the same as all the other grout joints. I know you don't want that one joint to stand out. You fudge that joint and it won't matter as long as the filler is flexible.

When I lay the vertical tiles, which will be touching the dirt (and therefor subject to lots of moisture, is there anything I should do, other than just laying the tile in?
No problem there. I'll will tell about a small trick that I do. I backbutter the vertical tiles and I draw the grooves across the tile (top to bottom) so that they are definitely vertical. This way, if moisture should get behind the tile it will have an opportunity to drain. Your objective is to have 100% coverage with the thinset but that doesn't always happen. If the grooves are horizontal or on a funky curve they can trap water and freeze and that can pop a tile.:)
 
#25 ·
slate doesn't have the strength to hold weight unsupported therefore don't 'hang' it over the edge or it'll chip off,,, when you're all done w/the job, SEAL IT to prevent water from penetrating the grout & eventually building up enough moisture to expand (ice) in lo temps thereby lifting all your very fine work off the substrate :furious: always a bummer to me BUT very profitable repairing it :thumbup: i like mixing some acrylic latex 'milk' into the mortar to 'tighten' up the jnts
 
#26 · (Edited)
SS,

A 3/16" cantilever won't hurt a thing unless that micro-spot takes a direct-hit from something heavy and sharp. Don't worry about maintaining a 1/4" grout joint everywhere, you can do it safely.

Sealing grout DOES NOT waterproof it.:)

Adding additives to already modified grouts can wreck the chemistry of the product and yield the formula non-functional. Don't add anything to the grout if it is already fortified.:)
 
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