[Keith N]

I'm doing a permeable flagstone patio and using granite chips for the joints. What do you think will help keep the chips in the joints? I'm looking at mixing sand with the chips and cleaning the excess sand off in addition to watering the chips to help draw them down in the joints.

[FungusMudGrub]

Not familiar with granite "chips" - what size(s) are we talking here?

[AZTLANLC]

Do a search for everstone they use an epoxy that binds small stones together and it's permeable, this is what you might be looking for

[Keith N]

Originally Posted by FungusMudGrub

Not familiar with granite "chips" - what size(s) are we talking here?

3/8 trap rock is what we use for our permeable paver jobs.


AZ, thanks I'll check it out.

[dayhiker]

I have the same question. I have a flagstone patio with joints of 1" to a few at 4". I was using Gator Dust but 1 bag went maybe 20 sf. The vendor told me joint area, not overall area so my 4 bags @ 30 went to 24 bags. No one around Birmingham, AL seems to have heard of decomposed granite. Most everyting here is limestone. I did talk to one crushed stone place that had "stone sand" which is limestone fines. He said their Auburn, AL plant had granite fines. Based on what I've been able to read, both of these sound like they'd be ok to use. Can anyone confirm?

I have about 500sf under a deck. Half the deck has a roof and half does not. I have about 100sf in a exterior firepit. The stones are sitting on about 3" or so of sand. The flag is called Alabama Bluestone. It's a light to medium grey sandstone.

Questions:
1. See above, limestone or granite fines ok for my application? Is one better than the other?
2. Would these materials be fairly stiff in the joints? I will have patio furniture on them. Joints are tight in these areas.
3. Would it be ok to mix mortar in at maybe 1:4 or so to get a harder surface but one that is not actually concrete? I read on another thread that polymeric sand has some portland in it. Since I'm on sand it'll still need some give but was thinking a little mortar or portland might stiffen it up a bit.

Any thoughts?

[stratis]

Hi,
for 1" flagstones on a 3" bed of sand (over concrete slab) with 1/2 to 1" spacing I was told to use Gator Polymeric stone dust as a grout but it's $39 a 50lb bag.
Any suggestions for a less expensive grout that could work as well?
Thank you

[dayhiker]

I wound up doing mine last week. I got half a yard of 8910 which is a limestone crusher run. The material is pretty fine. I'd say the biggest stuff is 1/8" or 3/16". I have buff mortar on the brick on my house and wanted a sandy color between the flag so I bought more buff mortar mix. I also had some portland cement at my house. I did 5 parts 8910, 1 part sand, 1 part buff mortar mix, and the final part about 50/50 buff and portland. I mixed it up really good and put it in the joints. I swept as much off the flag as possible. When I wet it I still wound up with a good bit of mortar on the stone. I kept going back with the hose on a mist setting but just couldn't keep ahead of it. The next day I did the 100 sf of the firepit. This time instead of wetting the whole thing, I put the hose on mist to spray off the flag and then misted teh whole thing. I probably added 1/4 the water that I did with the main body of the flag. I probably didn't add enough water to fully hydrate teh cement, but it seemed to work better in the short term. We'll see how it looks after winter.

[Keith N]

Were you looking for permeability? If so I think you just lost it with that type of joint material.

[glaciator]

This is a constant battle I have with people. They want the "finished" look of a mortared joint (and the cleanliness of it too), but they know it does not last here in colorado's winters (freeze thaw). The mortar eventually gets water under it and is costly to repair. So, I do dry set flagstone (with 1/2" hand chiseled joints or less) and brush in what is called "breeze" here in Colorado. It is a crusher fine in either red, gray, or tan (to match the flagstone color). It is ultra fines with up to 1/8" material in it and can set up a little like mortar, but is permeable and allows the stone to move with freeze/thaw cycles. It works great, but there is always a little that comes up (i.e. it can never be perfectly clean for very long). Wind and rain can pick up little pieces and move them onto the flagstone. I hose mine down every couple weeks or use a blower. I guess some people don't realize that THINGS NEED TO BE MAINTAINED!

Cheers,

Dave

[Keith N]

Dave, what type of rock is it? Granite, limestone, sandstone?

[glaciator]

I am pretty sure it is a crushed andesite. It might be dolomite. Either way, it is basically crusher fines of a particular color to match or contrast the stone.