Flagstone For A Driveway

natural1

Hi Everyone,
I am new to this forum and by reading through many of the posts it looks like I'm in the right place.
A little background: I am a landscape contractor and me and my crew do a broad range of stuff. Several times a year we do masonry type work. Flagstone patios and walkway, stacked stone walls (block mortared type) etc.
I have recently been given the opportunity to do a very large stone job. A big part of the job requires laying a flagstone driveway using Pennsylvania irregular flagstone. Thats what it is called here in NC.
My question is what is the best way to lay this considering the amount of weight and abuse it will take? The concrete base will be 5" on reinforced concrete poured over a compacted gravel base so that should not be an issue. I guess my specific question is what type of mix should I use for the mortar bed and what type of mix should I use for the mortar joints. BTW the stone will be 11/2" - 2" thick.
Appreciate any advice.

Thanks,
Mike

tkle

Sounds like good base.I like about a 2.5-3/1 masonry sand to common cement,with about a cup of glue per bag.Thinset the backs of your stone making sure each is clean first.Tuck point your joints to about 1/2" deep after laying,making sure the edges are packed underneath.
Grout,I use about 2/1 30 and 60 grit silica sand at a ratio to common cement of 2.5/1.Use a rubber bucket to measure sand and cement to make each batch semi consistent.A little will go a long ways
Check past threads for more info.There's been some good discussion on the matter already.

Tscarborough

In your area, and with that situation, you are looking for 2 properties for your mortar, both bedding and joint. You want a high bond strength and you want a very low absorbtion rate. Compressive strength is meaningless in this application.

A Type I portland/Type SA lime mix, porportioned to a Type N mortar (1 part portland, 1 part lime, 6 parts sand) would work very well. The grout joints should be tooled, and a penetrating (not surface) sealer can be applied. Full bedding of the stone, if possible, will probably prevent problems down the road as well. Is that stone "hot" or "cold"?

POOLMANinCT

tkle: glue?????????? same as milk?

tscar: hot or cold?????????

ty
ray

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Tscarborough

Hot=porous, absorbative, sucks the moisture out of the mud. Cold=dense, not absorbative.

tkle

latex additive

natural1

thanks for your replies. I was considering using some acrylic to add some elasticity. I have never used it so I am doing some research on the matter.

I would say the stone is on the dense side.

"A Type I portland/Type SA lime mix, proportioned to a Type N mortar (1 part portland, 1 part lime, 6 parts sand) would work very well"

Tscar, would this be the same as using the bagged of Type N mortar. Or is there an advantage to mixing the portland and the lime?

Also, is there any easy way to find any past discussions on this subject without having to scroll thru all the past posts.

Thanks again,
Mike

PS I found this quote on the internet and thought it made a lot of sense. "Bond is probably the most important single property of a conventional mortar. To obtain optimal bond, use a mortar with properties that are compatible with the masonry units to be used.' After the initial rate of absorption (IRA) on a particular unit is determined, the mason can decide which mortar best suits the needs of the project."

Tscarborough

It is not the same (Type N bagged VS portland/lime MIXED to type N). Type N is a strength designation; it can be achieved in many ways. That is why I asked about the rock, since I am not familiar with that particular stone.

natural1

I would describe the stone as a medium to hard sandstone, 2" in thickness.

natural1

BTW I did find a previous post on mortar mixes. Very helpful.

tkle

I'd be a bit worried about wear in a driveway.Some sandstone tends to scale off.Also tire marks show up pretty good,especially on the lighter stuff.It can start looking pretty bad real quick.I would lean towards a harder stone.As far as bond with sandstone,just wetting the bottom will slow down the absorption from the mortar greatly increasing bond.

jvcstone

If the stone is that Penna. blue/green stuff, I don't suspect that you'll have any wear problems--at least not in this lifetime. Wetting the bottom is always a good idea when doing flat work with porous stone. Also skimming both the stone and slab with thinset really helps insure good bond, -- the latex concrete bonding agent can do the same thing.

JVC

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www.jvcstoneworks.com

Vinny

Our specialty is residential driveways for the high end market. In that market our clients are constantly trying to out do each other, thank God. We have done flagstone on concrete as a driveway surface and while i was hesitant because of what I thought would be a wear problem, they have stayed just fine. We normaly use what is considered or called "select blue" because it has little to no surface fishers and seems to hold up the best.

The 5 or 6" slab will be fine as long as the supporting sub soil / sub base is firm and stabile. Use plenty of rebar too. The thin set or wha ever to glue it down is a must also.

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Driftwood

Some great advice , We just did 1400 sq. ft. of irregular bluestone on walkways or patios. washing the bottoms is a must1 Also is the glue,or You'll
have loose flags. The 7" blades in the 4 1/2" grinders will save on blades. Use water when cutting! Do a search qne month ago on this masonary forum.
I learned a lot. The masonary forum has a great crew of smart and giving Lads!

natural1

thanks for all the great responses. I feel confident about doing the job properly.
Several of you suggested thin setting the back of the stone. Does this mean buttering the back of the stone with the mortar mix or using actual thin set? Like tile thinset?

Apparently a gravel base will be set under the concrete driveway. I rarely see this done around here so I am glad to see that this will be done.

Yea, I am a big fan of the 4 1/2" grinder with the diamond blade. Use it a lot. Also, the concrete saw some. Typically do more cutting than chiseling. Not very old school I guess.

I will be hiring some masons for this job considering it has about 4000 sq. ft. of flat work. Some columns and stone walls also.

The Driveway, Brick walkway (set in sand) will have a Belgium block border. About 800 linear feet. Anyone have a standard labor rate for installing Belgium block? The footing will already be installed.

Thanks,
Mike

tkle

The same thinset as for tile.I use it on the bottom of the stone,leaving it away from the edges enough to grab the stone without getting my hands dirty.
What are Belgium block?

natural1

Sorry Belgian block. Spell check error. Also known as granite cobbles. Will be edging the drive with 11"x7"x3".
Thanks for the thinset tip.

stacker

i know this is off the subject,but i have to mention this.i tried the 7" blade on a 4 1/2 in grinder.there is plenty of power,but i felt it was too dangerous to use.1st there is no guard for the blade.2nd,it weaves too much.it almost takes both hands to use it.
just my observation on the 7' blade on a 4 1/2" grinder.

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jvcstone

Probably the most important safty issue when using any grinder to spin a blade, is to not exceed the rated RPM'S of the blade. Usually, unless you have a variable speed grinder, the 4.5, and 5 inch grinders spin too fast for the seven inch blades, and they have been known to come apart--not the best event with,or without a blade guard.

JVC

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www.jvcstoneworks.com

Tscarborough

Diamond blade segments will kill you, FYI.