Congratulations on your prospective project. For any outdoor project in any climate the adhesives must be cement-based. My favorite is Mapei's Ultra Flex II. Others may have their favorites - I've had such wonderful results w/Mapei's polymer modified mortar, that I can't recommend it enough. Their grout is the same wonderful quality.

What a wonderful idea! What are you going to mosaic? If its outdoors, don't do wood or anything else that will rot. And yes use thinset mortor. Slow is the expert, but I can't get Mapei's on the shelf up here in NH. But I've just found out that apparently I can ask Lowe's to order it for me. If your Lowe's doesn't carry it you could ask. Also in addition to mortor, grout, and tesserae; remember to budget for dust masks and rubber gloves for everyone; and tools to mix the mortar. If you plan to use BROKEN crockery, tiles or glass remember they will have sharp edges. If the piece will be where it can be touched, you might want to also budget for a way to smooth the edges. (It will be safer while you are making it too.) People who do a lot of this have small cement mixers for tumbling the pieces until the edges smooth. I have a small rock tumbler, and someone (Slow?) uses a icecream maker turned half way on its side. They can be shaken in coolwhip containers with water and a drop of dish soap but I don't know if you want to get into that. I say write a small mixer into your grant, why not? Someone here could make a recommendation on what kind, I'm sure.
Klinger's test for dishes is if they stick to your tongue after you break them, they are too porous to withstand winter weather. I stick to that rule. But I will say that I saw a conctete planter mosaicked by a woman's cooperative in Bethlem NH that had all kinds of crockery on it and it seemed to be holding up. But maybe they knew about the tongue test, lol. Glass is good because its not porous clearly.
Have fun and be sure to report back.
Kathy

Thanks for all the info. So the adhesive is the Ultra Flex II and the mortar is different? Why do you need both? Do you use the mortar on horizontal and the UF II on vertical?

So you break the crockery and stick it on your tongue? I'm not sure I understand that. I've just done small mosaics with leftover glass from my stained glass projects so I'm not knowledgeable on the pottery part.

We don't know what to mosaic yet. We were trying to decide. Thought a wall, or part of a wall, or build something with cement block.

I'll have to look into a mixer. Doesn't all the turning scratch the glass/tile?

I will look for Mapei's here at Lowe's.

Thanks again.

The Maipai ultra flex recommended by slow IS a thinset mortor I believe.

If the broken edge sticks to your tongue it is too porous. Break a piece and put it up against your tongue. If it sticks its because it is drawing water from your tongue its so porous. I don't understand totally either, since if the edges are covered by mortor and grout you'd think the wet weather wouldn't get in. But people say it does so I don't want to have my hard work ruined.

To find out how to tumble glass and dishes etc in a mixer, you could do a search here at this forum and if you don't find answers, ask another question. The search is on the main page at the bottom.

Below is a link I found by searching for mixer
There were other links too.
Good luck
Kathy

Here is a link that might be useful: Tumbling glass etc

Ultra Flex II is the adhesive - a polymer modified professional grade mortar. I don't tumble crocker - mostly bottle glass, nor worry about climate. I use anything and everything I find for tess.

In addition to the wonderful advice you're getting here, I might suggest you also see if you could get a local tile person to help you with your project. It could be a local mosaic artist, or just someone who has done exterior tile work, like swimming pools or stone patios. With a project of the scale you're suggesting, I think your chance of success would increase if you got some local assistance. A tile company might even donate some products or services.

Excellent idea, LORI:

Thanks so much for all your advice! I'll have to look around for a tile company. That is a great idea. The project isn't slated until next year if we get the grant. I'll keep you posted.
Becky

Eve Lynch of Kraken Mosaic in Fort Myers, FL is working on one now. I don't know the details of how she handles it, but I do know that she puts out a call to artists and then mosaic artists from all over send her little pieces on mesh and she installs and grouts everything. If you go to my blog and go past the top entry (Saturn) you will see the butterflies I did for her latest one, a cloud of butterflies at the Calusa Nature Center and Planetarium.

Here is a link that might be useful: Silva's blog