Flagstone grouting question

[SteveB]

I recently had 11,000# of flagstone spread out in my yard in the approximate way I wanted it. There are big gaps in it, so I am trimming stones, and making it fit better. Some places need to be tight, others, not so tight.

Next step is to make it flat and fill in the cracks which is where I need some opinions.

What type of sand is good for placing under these so they don't shift. I have used some reject sand on some pavers, and it seems fine. I live in Las Vegas, and the soil is dry and sandy. Not a lot of water to speak of.

What type of sand/mortar/portland/decomposed granite would you use for the cracks. I have some Ortho books, and they suggest different things. I want something that is durable, and won't crack or flake readily, I figure I will have to do some future repairs in PourStone, but no biggie. I want the fill to come up to about 1/8" of the flagstone to create a level walkway, and so the dogs don't turn an ankle or bust a toe.

Would you use:

decomposed granite a mix of sand and portland grout mix applied with a grout bag

Something else?

????

I want to do this once and do it right.

TIA

Steve

[Roger]

Shoulda written this query when you were contemplating the project...... You seem to have gone about this in the wrong order. First you grade the area to be covered with stones, then you put down, e.g. 4-8 inches of 3/4" angular gravel, tamp it well and level it, add a few inches of g-sand or sharp sand as a base, smoothe it, grade it, pack it down. Once flat, *then* you buy the stones! You will not be happy with the result if you simply pack a little sand under the existing stone pattern, it will not be stable when trodden upon, and will not work with any setting type mortar, unless you have a concrete pad poured underneath. Best source of exactly what materials to use as underlay is a busy landscaping materials center, and I don't mean the big box stores.

[SteveB]

I am sorry. I must have missed something. How does all this apply when the stones vary in thickness?

Steve

[Roger]

First, get a good book on masonry, with emphasis on patio building. Stones are set, depending on how uneven they are, by either whisking away sand to match the uneven underside of the rock, or putting weight on the rock and jostling/twisting it to settle evenly in the sand. Even after the sand is dampened and tamped, it easily accomodates the rough undersides of flagstones.

[Roger]

I suggest you have a look at Home Depot mag. section, and buy or browse a good DIY book on masonry, with emphasis on patio building. Stones may be set, depending on how uneven they are, by either whisking away sand to match the uneven underside of the rock, then placing the rock,or just by putting weight on the rock and jostling/twisting it to settle evenly in the sand. Even after the sand is dampened and tamped, it easily accomodates the rough undersides of flagstones. Once that is done for the whole area, additional sand can be added to fill the joints. I used a sand at the supply co. called "g-sand" that looked like crushed fine limestone, and after winter rains it set up like soft cement, but there was some leaching of the lime onto the surface of the stone. Next time, I may use clean, or sharp sand.

[SteveB]

I have the Ortho book. Now that I have trimmed the stones, and have a 1/2 to 1" space, I was just wondering what to use to finish the final fill. I still have to take up the stones, and adjust the under layer of dirt to make them even on the top. We have decomposed granite here, which hardens a bit with time and weather. I am not so sure now of using anything that has concrete in it, as the lime may leach out and discolor the stone.

Trimming the remainder of the stones will take a couple of weeks, so I guess I will arrive at the final answer by the time I get to that stage.

Thanks for the pointers, all.

Steve

[m Ransley]

If you have a concrete base base and fill it can all be dry set so leveling is not rushed and watered to set when finished , mortar wont discolor stone , But a morter grout without a concrete base will heave and crack . But gravel or sandgrout will come out and be on the stones possibly. If you dont concete it in you may or may not like your joints in a few years. Your weather is important , here we go to -20, talk to local people see what they do . Your options are different because of weather than mine.