Anybody laid flagstone on a slab?

[DARISC]

I had a trellis that I designed built on a fresh 12'x20' slab. I want to lay flagstone, doing the work myself myself, using 1" thick gold quartzite flagstone (bought by the pound on pallets in piece sizes that are small enough to be easily handled by one person).

I plan on buying knee pads, a small Makita hand held saw & diamond blade, fitting the flagstone dry over the entire slab (leaving about 1/2" to 3/4" wide spaces for grout), then mortaring them in place, laying mortar for 3 or 4 pieces at a time, doing the grouting, using a grout bag, a day or two after all the stone has been set in mortar.

The slab has been saw-cut in both directions and I've been told to lay plastic slip sheet over the cuts to prevent the flagstone from cracking shoukd the slab crack.

Does this approach sound about right?

I have no masonry experience, but from what I've gathered, seems like a pretty straightforward process. Will I need a helper or is it a one man job?

Any advice, warnings, whatever?

Thanks in advance!

David


The trellis is built, the lattice arrives on Wed. The 4'x4' redwood lattice pieces will be left unpainted to go gray in the weather. They rest on 2x6 pieces nailed flush with the bottoms of the 2x8 rafters and cross pieces around the perimeters of each 4'x'4' grid opening. When it comes time for a repaint I'll lift out the lattice, hose it off and only have to paint the main structure.

[stomachmonkey]

don't know about the rest but is that thing gonna hold supported on one side only?

[LakeCleElum]

Dunno your climate, but if it freezes, it's recommended to put down a coat of "thin-set" over the slab before you mortar/stone. This will keep water from seeping thru and cracking and lifting your work. I don't like the plastic idea myself.

I'm in the middle of putting flagstone on the front side of the garage on my new house.

[gassy]

You should be good on your own, but a helper never hurts! In the CGI it looks like gutters--am I wrong? SM asked a good question about being supported on one side only. Looks cool tho. Don't know where you live but one ice storm and it'll be streching its limits I would think.

[look 171]

I wouldn't put plastic. Mortar will not stick to plastic. I don't know about colder area of the country since my experience is in LA. Mix a good thin set along with mortar. It sticks better. How's the back side of the stone? Is it flat? If not, try to butter the back to elimate any empty spots. As long as there are no hollow space, then you should be ok. 1" thick flatstone should be plenty strong. Try a diamond blade on a Skill saw or worm drive saw. I sometime have these guys cut the back side and chip the top of the finish edges to get a little more natural look instead of a saw cut. Just more work and more money.

If you are worry about cracking, you can get a crack isolating sheet and thin set it on the surface first. I really wouldn't about the cracks. Let it crack, it looks natural that way. I get a helper. How many sq'. I should ask, how's your back?

[Hetmann]

We did this in our front yard a few years back. We had a large slab for a front patio that was over 50 years old and we poured a second one next to it. These were tied together with rebar. We covered both as well as a long sidewalk with red flagstone, approximate area about 1200 square feet or so. Pretty big patio.

We had a mason install the flagstone. I believe he just used portland cement as a bed carefully leveling each stone, I do not remember any thinset. He also grouted with portland cement. As I recall, he did not score my old slab and the new slab was not highly finished. The patio has been through several freeze thaw cycles and has developed some cracks. We have a crack or two through stones where the two slabs meet, however the majority of cracks have developed in the grout lines and folow the edge of one or more stones. On the whole it has held up very nicely. We have had a little spalling of some flagstones, but nothing major.

[DARISC]

Originally Posted by stomachmonkey

don't know about the rest but is that thing gonna hold supported on one side only?

Originally Posted by gassy

In the CGI it looks like gutters--am I wrong?

Gutters? Don't understand.

SM asked a good question about being supported on one side only. Looks cool tho. Don't know where you live but one ice storm and it'll be streching its limits I would think.

When I showed the rendering to my contractor he said "that's an OH NO YOU CANTILEVER!" I splained to him that the cantilever is extreme but that the front fascia board across the rafters will be depleted plutonium (verrry heavy!)

Seriously, it's attached to the back of my house .

Originally Posted by LakeCleElum

Dunno your climate, but if it freezes, it's recommended to put down a coat of "thin-set" over the slab before you mortar/stone.

I'm in Carlsbad, CA (San Diego County - desert/Mediterranean climate). Will I still need to spread thin-set?

Originally Posted by look 171

Mix a good thin set along with mortar. It sticks better. How's the back side of the stone? Is it flat? If not, try to butter the back to elimate any empty spots. 1" thick flatstone should be plenty strong. Try a diamond blade on a Skill saw or worm drive saw.

I have in mind buying one of these;



Is it flat?

Pretty flat, both sides. I'd figured buttering the backs w/1/2" or so, then setting them in place. Do I need to lightly butter the slab where the stone will sit also?

you can get a crack isolating sheet and thin set it on the surface first.

Yeh, that's what I meant - not plastic.

I sometime have these guys cut the back side and chip the top of the finish edges to get a little more natural look instead of a saw cut.

I like that tip a lot! Time's really not an issue. I'm a painter/sculptor and the only reason I'm not paying a mason to do this is so it'll look like what I want it to look like - may even incorporate some mosaic work, a compass card or...?

I really wouldn't about the cracks. Let it crack, it looks natural that way.

I thought about that. But I won't know if cracked flagstones will bother me until I see them - and if I don't, then it'll be too late.

I get a helper.

Yeh, a young guy works at the stone yard is available. When I first asked him if he did any moonlighting he said "What's that? The second yard I went to for an estimate, the young guy asked the same thing! WTF !

How many sq'.

12'x20', 240 sq'.

I should ask, how's your back?

Strong - 5' 13 1/2'', 220 lbs .

Originally Posted by Hetmann

We had a mason install the flagstone.

Did he work alone? Recall how long it took?

As I recall, he did not score my old slab and the new slab was not highly finished.

Slabs (4" in my case) crack, even here in SOCAL, even though it's warm. The concrete guys all strongly recommend saw-cutting.

We have a crack or two through stones where the two slabs meet, however the majority of cracks have developed in the grout lines and folow the edge of one or more stones.

Do the cracks through the stones bother you - visually?

On the whole it has held up very nicely. We have had a little spalling of some flagstones, but nothing major.

I guess spalling is to be expected more in colder climes. At any rate, I can live with Mother Natures whims if she spalls me .

[LakeCleElum]

Since you're in southern CA, you could skip the thin-set. I'd still would not put plastic down, you want your mortar directly on the slab. Also, tab each piece with a rubber mallet as you set it...

[DARISC]

Originally Posted by LakeCleElum

Since you're in southern CA, you could skip the thin-set.

Great.

I'd still would not put plastic down, you want your mortar directly on the slab.

Yeh, I meant, like look 171 said, "a crack isolating sheet", just over the saw cuts.

Also, tab each piece with a rubber mallet as you set it...

I'll have one of those on hand and a long level. Do I have to spread any moter on the slab under the buttered stone before I set it into place?

Thank ya'll for all the tips.

..

[LakeCleElum]

Originally Posted by DARISC

Thank ya'll for all the tips.

..

Yes, Using a trowel, put a thin layer of mortar on the slab and then put some on the bottom of the stone, like you're buttering bread; may 1/4 to 3/8 inch think on the stone. Put the stone in place, lightly tap it and move to the next one. As you progress, your mortar will dry out. Add small amounts of water to keep it like you started; a little thicker than oatmeal.

[trekkor]

The most important thing is making sure the back of the stone is clean and dust free.

You can grout as you go.

Use acrylic in your mortar.

Mortar should be 1" thick or so.


KT

[DARISC]

Originally Posted by trekkor

The most important thing is making sure the back of the stone is clean and dust free.

So I've read.

You can grout as you go.

That's interesting - never read or heard that. That'll be inspiring to this amateur as I can finish each session. When you grout as you go, can you use the same morter used to set the stone?

Use acrylic in your mortar.

What do I buy? What proportion do I mix in? Is it powder or liquid?

Mortar should be 1" thick or so.

Great - I was unsure of how thick to butter the stones.

Thanks Trekkor. I gather from what Ive read on this forum that when it comes to this craft, you da man!

..

[trekkor]

The setting mortar is a premixed 'Masons Mix' or you can make your own.
1 part cement, 3 parts sand and 1/2 part lime. I use 2qts of liquid acrylic ( Hydroment multi purpose) per 150#'s of dry mix.

This is a great material for grouting. Use a sponge to 'tool' the joints and wash the stone.
Rinse the sponge regularly. take care not to wash excessively or you will end up with an exposed aggregate like appearance.

If you want to use a colored grout after the entire patio is complete, you might want to acid wash the surface first with a mild dilution.

I'd wait a few days after that and pre-seal so the grout releases out of the clefting in the stone.
A few days later, re-seal.

how thick to butter the stones

Put your mortar on the slab. Imbed the stone into it and tap into place with the mallet like was mentioned. Have a level handy to lay them flat in relationship with the adjoining pieces.
The mortar will squeeze up between the stone. Add mortar with a pointing trowel, let set for 10-15 minutes so it can set up a bit before you wash it if you grout with the setting mortar.

Sort your stone by thickness.
I'd start on one side with the thickest first, using slightly less mortar, then move across your slab.


KT

[look 171]

So not buy that Makita cordless saw. It will take aboout 2 years to cut your 1" thick slab. That thing is good for cutting a little of 1/4 thick tile. You need a saw with a bit of power. Check out a worm drive saw. They run a about $160 at home centers, I like skill or Bosch. Pretty much the same saw. A 4 1/2 inch angle grinder will work. but slow for 1" thick stuff.

Am I getting this right, you want to saw cut the slab that's already there? Expansion joints? Why. If its an old slab, and it isn't crack, what make you think that it will crack with the flag stone? YOu want to set it directly on top of an the slab that's there, right?

Jeff

[DARISC]

This PPOT gang is incredible! Here a total stranger (with vociferous political leanings contra to the majority here ) gets the support of a quality one usually expects only from family and the closest of friends! I hope I'll eventually be presented with the opportunity to respond in kind to you guys.

So,uh....more questions and clarification .....

Originally Posted by trekkor

The setting mortar is a premixed 'Masons Mix' or you can make your own.
1 part cement, 3 parts sand and 1/2 part lime. I use 2qts of liquid acrylic ( Hydroment multi purpose) per 150#'s of dry mix.

Does "Mason's Mix" contain acrylic or is that your custom mix just for the grout to increase its imperviousness to water, give a nicer finish?

This is a great material for grouting.

"Mason's Mix and your acrylic mix? Or just the latter?

Use a sponge to 'tool' the joints and wash the stone.
Rinse the sponge regularly. take care not to wash excessively or you will end up with an exposed aggregate like appearance.

Is an exposed aggregate appearance always undesireable? Or can that appearance be used purposely?

If you want to use a colored grout after the entire patio is complete, you might want to acid wash the surface first with a mild dilution.

I'd wait a few days after that and pre-seal so the grout releases out of the clefting in the stone.
A few days later, re-seal.

I'm unclear about sealing. I've been under the impression that sealing wasn't necessary. What is the sealant? Is it brushed on, being careful to avoid getting any on the flagstones?

Put your mortar on the slab.

Spread how thick on the slab (I know you said butter the stones with 1" of morter)?

Imbed the stone into it and tap into place with the mallet like was mentioned. Have a level handy to lay them flat in relationship with the adjoining pieces.
The mortar will squeeze up between the stone. Add mortar with a pointing trowel, let set for 10-15 minutes so it can set up a bit before you wash it

Wash it?

if you grout with the setting mortar.

Ah so! The setting morter can be used as the grout,

Sort your stone by thickness.
I'd start on one side with the thickest first, using slightly less mortar, then move across your slab.

I'm not comprehending the above. The flagstones I'm buying vary slightly in thickness, but not much - pretty close to 1" consistently. Don't understand what you mean by "start on one side with the thickest first". I'm planning to fit and lay all the stones dry over the entire slab, then setting them. Seems this will involve selecting stones sequentally based on how they best fit to adjacent stones rather than based on their thickness - I'm sure I'm a bit thick myself on grasping what you're saying.

..

[DARISC]

Originally Posted by look 171

So not buy that Makita cordless saw. It will take aboout 2 years to cut your 1" thick slab. That thing is good for cutting a little of 1/4 thick tile. You need a saw with a bit of power. Check out a worm drive saw. They run a about $160 at home centers, I like skill or Bosch. Pretty much the same saw. A 4 1/2 inch angle grinder will work. but slow for 1" thick stuff.

Thanks for that tip. I've built many stained glass panels and am familiar with scoring and breaking, and, with slab glass, chipping with hammer blows to close in on a shape. I'd intended to use the Makita I showed only for tight, small scale detailing where necessary. Still a bad idea? Do I really "need" a power saw at all? Primitive peoples laid a lot of flagstone before electricity was ever discovered .

Am I getting this right, you want to saw cut the slab that's already there? Expansion joints? Why.

It's a 2 week old, 4" slab. It was saw cut with a Skil Saw w/diamond blade to a depth of about 1 1/2" into quadrants a couple days after it was poured. It's s.o.p. with slabs, in this region at any rate.

YOu want to set it directly on top of an the slab that's there, right?

Yup.

Am I trying youse guy's patience with all my question?

[trekkor]

The pre-mixed mortar has no acrylic. You'll need to add your own.
Most people do not use it at all.

When you 'wash' your grout that is when you use a wet sponge and clean the wet mortar off the adjoining surfaces of the stone.

There will be no buttering of the stones ( jedi hand wave ).
Mark around the stones while they are sitting on the slab before you apply any mortar. Like one of those crime scene body chalk outlines!
Apply your mortar inside you lines.

Do you have your flagstone? Unless one side of it is 'guaged' or flat from the quarry it will be varying in thickness. If not, it is OK to set either side up. ( there is no top or bottom )

Variations of 3/4" to 2" are not uncommon...On the same piece at times!

It's time consuming HARD work. DO NOT RUSH!!

The Makita hand held diamond saw has no place on this job. Save it!
An angle grinder or Skil saw with a dry diamond blade is the way to go.

You'll need a 'rock hammer'. It has two ends.
One end has a square, heavy head for breaking and the other has a long flat blade for chipping or splitting pieces.

Also, let you slab cure out for a couple more weeks before doing anything.


KT

[look 171]

Originally Posted by DARISC

Am I trying youse guy's patience with all my question?

You don't really need a power saw if you want to just use a hammer and a chisel. That's not for me. too many broken stone if one's isn't careful. Buy a saw and you'll get done 10 times as fast and dead on with the cuts.

Here's one you can return for me. Do you know anyone up here around LA or Pasadena that can fix a stain glass door for me? Where are you again? S. Diego?

By the way, just be glas I can help.


Jeff

[DARISC]

Originally Posted by trekkor

The pre-mixed mortar has no acrylic. You'll need to add your own.
Most people do not use it at all.

I'll use bags of pre-mixed I guess. Do I understand correctly that I can use that same mix to grout as I go if I decide to do that? I probably won't though because I'm not crazy about gray and would really like to add an earth tone colorant to the grout. If I can use pre-mix for grouting, is adding colorant as simple as it would seem to be?

When you 'wash' your grout that is when you use a wet sponge and clean the wet mortar off the adjoining surfaces of the stone.

I see - but I'm still unclear about "sealing, resealing".

There will be no buttering of the stones ( jedi hand wave ).

That's a relief - was picturing morter dropping off buttered stones while in transit to their landing spot, making a mess of "cosmic" proportons .

Mark around the stones while they are sitting on the slab before you apply any mortar. Like one of those crime scene body chalk outlines!
Apply your mortar inside you lines.

That makes so much sense - the slab is broom surfaced so I guess a fat lead carpenter's pencil or chalk will work, eh?

Do you have your flagstone? Unless one side of it is 'guaged' or flat from the quarry it will be varying in thickness. If not, it is OK to set either side up. ( there is no top or bottom )

I looked at what I want at the stone yard but haven't ordered it yet. It's not been guaged but can be laid either surface up:



Category: Flagstone / Random
Description: Light silver base with splashes of gold flecked with mica.

I'll probably buy 2 1/2 tons which will hopefully allow for breakage and leave some that I'll use in a future water feature that I'm planning.

Variations of 3/4" to 2" are not uncommon...On the same piece at times!

It's time consuming HARD work. DO NOT RUSH!!

Finally - hearing it from a pro - I'll BET it's hard work and I won't be rushing.

The Makita hand held diamond saw has no place on this job. Save it!
An angle grinder or Skil saw with a dry diamond blade is the way to go.

Great. I own a Skil saw. Would buying an angle grinder be a lot better?

You'll need a 'rock hammer'. It has two ends.

Which end should I use?

One end has a square, heavy head for breaking and the other has a long flat blade for chipping or splitting pieces.

Also, let you slab cure out for a couple more weeks before doing anything.

Yeh, it'll be a while. I've got a 10'x20' garden studio about to be built first on another slab 14' off my patio slab

KT

Originally Posted by look 171

You don't really need a power saw if you want to just use a hammer and a chisel. That's not for me. too many broken stone if one's isn't careful. Buy a saw and you'll get done 10 times as fast and dead on with the cuts.

I was thinking - I'd probably break a lot of stones (and they ain't cheap) so I'll use my Skil saw - as I mentioned above, wondering if I should buy an angle grinder.

Here's one you can return for me. Do you know anyone up here around LA or Pasadena that can fix a stain glass door for me? Where are you again? S. Diego?

I haven't been involved in stained glass for over 20 years, but I called a supplier in San Diego (I'm about 35 mi. north in Carlsbad) that I'd used for years when I lived down there. I was surprised to find they're still thriving. They recommend Beveldine for repairs. The company has been in business for as long as they have and do good work, including repairs:

http://www.beveldine.com/

http://maps.google.com/maps?hl=en&um=1&ie=UTF-8&q=BEVELDINE&near=Long+Beach,+CA&fb=1&sa=X&oi=local_group&resnum=4&ct=image

Hope this is helpful.

By the way, just be glas I can help.
Jeff

..

[KFC911]

Originally Posted by DARISC

This PPOT gang is incredible! Here a total stranger (with vociferous political leanings contra to the majority here ) gets the support of a quality one usually expects only from family and the closest of friends!....

It might be a set up...we have read your posts