How to lay flagstone on new concrete patio?

Page 1 of 2  
Hi, I just finished pouring concrete for a small patio (4ftx7ft) this evening. How long should I wait until I lay flagstone onto it? A full 28days? Also, what type of mortar glues the flagstone onto the concrete? Thinset?? What about grouting between them? Thanks for all responses! Theodore
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 10/2/2010 9:57 PM, millinghill wrote:

If you wanted a flagstone patio, why did you pour a slab? If it freezes where you are, at some point water will get under them, freeze, and pop them loose. Around here, flagstone patios are laid on a sand bed, with the grout lines done with something that locks together, but still passes water.
--
aem sends...

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Fergeddabout it. The flagstone is in various thicknesses, and now that you have concrete, you will have to build up the concrete so that the top will be flat. Or live with uneven concrete.
The slab will not be able to drain except for at the edges now that it's a slab.
You can grout with any old grout by using a squeeze bag and carefully filling voids. It is going to impossible to get the grout into all the holes.
Said holes will fill with water, and freeze and thaw and freeze and your stone will come off in layers and chunks in the future.
You really planned this out, didn't you?
Steve
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

You've never worked with gauged stone, have you?

How do grouted joints drain on any patio?

What holes are you talking about?

You are making some assumptions. Flagstone is a broad term, and people use it to refer to many different types of stone. How do you know that he's not planning on using gauged flagstone? He'll be setting the flagstone in a setting bed of mortar - if that is done correctly, I don't understand where these holes are coming from. There will be complete contact between stone and mortar whether he uses gauged stone or not..

How is this any different than someone who bought a house with a concrete slab patio and wants to dress it up with flagstone? It's done all of the time and it's not a particularly big deal, is it? You play the hand you're dealt - he's been dealt a slab. It's there. Move on to how to deal with it.
More to the point - it's a farkin 4' x 7' patio! Even if the thing blows up on him (no reason it should), it won't exactly ruin the guy's life. The stone can be pulled up and can be reused. We call this a learning experience. If the OP doesn't go off half cocked from here, there's no reason he needs to have a difficult learning experience.
R
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Why did you pour a slab to put flagstone on it?
Jim
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
replying to JimT, drgnslayr wrote: You have to use a concrete base if your installing flagstone on clay soil. if you don't you will experience major buckling probably after your first big rain storm.
You want a 4" slab with steel mesh and rebar, on 3" of compacting concrete crush.
I'm in the process of doing one of these now. A 3,000 sq ft flagstone patio around a pool. The soil is clay. All the water drains either in floor drains or off the edge into perimeter drains to prevent too much water edging in around the perimeter.
There are no short cuts in laying stone. Those short cuts always come back to cost you in the end. Would you prefer spending more now to do it right, or have to re-do it in 5 years or less? How costly will that be? And also disrupting your life.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Wed, 07 Sep 2016 21:14:01 +0000, drgnslayr wrote:

Well, since he did it *SIX YEARS AGO* it must _already_ be a crumbling mess. Right? Thank you for that advice.
Why don't you HomeOwnersNoobs ever read the damn dates of stuff you reply to???
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Wednesday, September 7, 2016 at 5:24:36 PM UTC-4, Sam Hill wrote:

I don't get it either. If you look at the thread over there, it's clearly marked with the date. Then again it could be spammers who revive it to generate traffic for Home Moaners.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I'm with aem in wondering why you went to the expense of a concrete slab to produce a poor base for flagstones. What part of the world are you in? Is that how it is done there?
Too late now- but I'd have gone with flagstones on the *well prepared bed*, or stamped concrete.
Based on my experience in freeze/thaw country I'll answer the questions with best guesses-

A few days should be fine.

I'd probably go that way at this point. Though an argument could be made to float the flagstones on top of the slab so when it cracks, the flagstones might survive- and give on the grout lines.

That's kind of like asking 'what color car should I buy'. First you need to decide how thick your flagstones are- how wide you like your grout lines to look- then whether you want it to be smooth, gravelly, or colored.
Once you decide on an effect- then ask how to achieve it.
Jim
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sat, 02 Oct 2010 18:57:58 -0700, millinghill wrote:

Bust up the concrete and re-pour it then stamp a flagstone pattern in it. Nobody lays flagstone on concrete. Not at least on planet Earth.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

There are reasons that it would be done that way. Just because you haven't encountered them, doesn't mean there aren't valid reasons. In any event, your advice is not advice, and that's what the OP was asking for.
To the OP - you could use thinset or the same mortar that's used in block laying. Mortar would be cheaper. If you are in freeze/thaw territory you might want to add a latex additive to give the mortar more elasticity and to improve the durability. You can lay the flagstone, ummm, right about now - as soon as you can walk on it. The setting mortar could also fill in between the flagstone -it's not a necessity to do it in two steps, but it's probably easier to do it in the two steps.
http://www.the-flagstone-experts.com/laying-flagstone.html
R
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sun, 03 Oct 2010 07:57:44 -0700, RicodJour wrote:

How many have you encountered?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

A few. Things that required concrete - the owner already had the slab (like the OP does), soil conditions, traffic load, drainage conditions (separate from soil conditions), climate conditions, etc. Alternatives to a concrete slab can be compacted soil cement or sand/ cement. Price and local conditions usually determining the tipping point between the choices. On a 4' x 7' patio (~1/3 cubic yard) the potential price and labor difference would be minimal.
To further your education: http://www.askthebuilder.com/536-Flagstone-Set-on-Sand.shtml http://www.contractortalk.com/f7/flagstone-concrete-11374 / http://www.irwinstone.com/more-information-flagstone-on-concrete-base It's quite surprising how many hits I got from stone yards. Well, maybe surprising to you, but not that the people who deal with the stuff on a daily basis know what they're doing.
Flagstone can be dry set, most of the time, but there is abso-farkin- lutely nothing wrong with putting it on a concrete slab, so if it's not ever done that way on your planet Earth it seems you planet is in the Bizarro realm.
R
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

There are reasons that it would be done that way. Just because you haven't encountered them, doesn't mean there aren't valid reasons. In any event, your advice is not advice, and that's what the OP was asking for.
To the OP - you could use thinset or the same mortar that's used in block laying. Mortar would be cheaper. If you are in freeze/thaw territory you might want to add a latex additive to give the mortar more elasticity and to improve the durability. You can lay the flagstone, ummm, right about now - as soon as you can walk on it. The setting mortar could also fill in between the flagstone -it's not a necessity to do it in two steps, but it's probably easier to do it in the two steps.
http://www.the-flagstone-experts.com/laying-flagstone.html
R
--
<heh>

That's why I asked "why". It's a very small patio and seemed like an odd
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sun, 03 Oct 2010 12:15:59 -0500, JimT wrote:

I can damn near put a sum of money in escrow to cover a bet that if the OP lives in an area subject to freeze/thaw, that the flagstone will loosen. If the OP lives in a temperate region then I redact my statement and apologize to the OP and everyone else. I'm not an unreasonable person but being a jack of all trades and having close friends that do concrete and landscaping and working in my spare time with them I understand the dynamics and I'm not guessing this and that will happen.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

The OP did not say he lived up in the frozen north. I have about 2300 square feet of flagstone over concrete and I wouldn't have it any other way. When you put stone over sand you end up with an ant farm and sprigs of grass growing up through your patio.
To answer the OP's question, you bed them in type S mortar that has a bit of bonding agent added to the mix. That also becomes the grout because you float it up flush with the top of the stone. The real trick is sponging off the tops at the right time.It is a fairly slow process but not too bad for a homeowner since you don't have to do it all at once. I suppose water could get under the stone and pop them up but you really should not end up with any voids if you are bedding the stone right. It doesn't freeze where I live so don't know.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sun, 03 Oct 2010 11:47:58 -0400, gfretwell wrote:

Well good for you. What the fuck do you want a door prize?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

No, of course he doesn't. He's just pointing out that you don't know what the hell you're talking about.
If you're going to give bad advice, grow some thicker skin.
R
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
replying to gfretwell, drgnslayr wrote: To prevent freeze/thaw situations where the stone pops up you need to think about two things. First.. make sure there are no air pockets between your flagstone and mortar bed... also in your grout. You need to wiggle the flagstones when you install them and use a mallet to tap them into place. Air pockets can later fill with water, which can freeze and pop your stone. Also... add a polymer hardener to your grout if it doesn't already have something in it. Last, use a quality seal product on your finished patio. You are trying to reduce the porousness of your grout.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Sorry to cause such dissention.
Here's clarification/details: House is in NY State. I've seen some houses in neighborhood with rectangular-cut flagstone steps (treads) set on concrete risers (definitely not sand) with some type of mortar between joints, leading to rectangular-cut flagstone porch at their front door set on something very hard (must be concrete). Definitely no grass or sand between joints... they're hard joints. I want to do similar. Hope this clarifies. Opinions appreciated.
Some replies below beg a technical rebuttal: are flagstone more prone to freeze/thaw popping than, say, ceramic or granite or terracotta tile?? I had terracotta tile on the previous porch for 20+ years without a problem. Opinions appreciated.
Regards, Theodore.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Site Timeline

Related Threads

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.