Need a flagstone expert’s advice…
I poured a concrete walkway and have started cutting and laying stone into a mortar bed. So far so good. Nice and level, looks great. Several questions have come up:
– It is getting colder out what are my worries here with mortar?
– My mortar selection was bagged standard strength Sakrete Mortar. Is this acceptable? Someone mentioned that this mix is not ideal and everyone seems to vary theirs from 3-1 sand on down. Should I be adding hydrated lime to this? If so, how much?
– How long can I wait to fill in the grout joints? Can I use the same mortar? I plan on mixing it a bit wetter to use a grout bag. Then after the entire walk is done fill in the joints with a colored grout to give it a darker gray appearance but I want to do it all from the same batch to get an even color. The stone laying is going to take weeks, can the joints go unfilled for that long?
– Flagstone steps… I had planned on cutting my own when the stoneyard told me that I should be using some insanely expensive burnt flagstone for treads. What am I risking by using normal flagstone?
– I had planned on buying normal cut flagstone for the treads and then making the edges have that nice broken look rather than cut. The stoneyard said that people use a torch on bluestone to get that look but regular flagstone isn’t dense enough. Thoughts on how to treat this edge?
– Risers first? I read everywhere that risers go on first then the treads. why? wouldn’t the risers help hold the step down? Or is it just not necessary? Any other way to guarantee the step won’t come loose?
– overhang. How much of an overhang should I plan for my step?
– what is the min thickness for steps that overhang?
– cement wash. All of my sources recommend washing the back of the stone with a runny portland mix to get it to adhere better. But on stones that I don’t do this with it looks just the same when I lift the stone back up. The soupy mix comes to the top. It seems unnecessary…
– when all is said and done are there any “don’t”s. Salt in winter? Shovelling with metal snow shovel?
Thanks!
Replies
Kinda what this sites about Les.
Sorry your not getting anything in return here for your investment. I for one get paid quit well for my time here in a number of ways.
In this case I too am interested in Seans questions.
Sorry Sean I don't have any answers but if you got a carpentry/cabinetry question I'm one of many guys here that will be quick to help. And for free. What a bargain. All anyone here would suggest is return the favor if you can. Otherwise don't woory about it.
Edited 11/10/2004 7:06 pm ET by JAGWAH
I see that you elected not to give any profile info...so please fill in the blanks!
where do you live?
what are the seasonal weather conditions/temps/rainfall, etc?
Secondly...the term "Flagstone" can mean lots of different kinds of rock of different qualities in different areas of the country....need more specifics?
Sakrete is formulated to meet the bare minimums....which means leaving out the things that make a "rich & buttery" mix.
Lastly mortar is for bricks/stone applied on a vertical wall...horizontal applications require a portland based sand mix to prevent freeze spalling.
Waiting to fill mortar joints in the winter months may mean water intrusion and subsequent freeze/heave/spall problems.
Design dictates the amount of overhang,
Kickers first is a good sequence,
thickness depends onthe density/strength of the stone,
Cement wash is a questionable...why not very clean and moist,
And salt is always deleterious to masonry and concrete products.
....................best I could do for you..............Iron Helix
Thanks for the reply...
I live in Northern VA.
Sakrete Mortar: I was under the impression that this was a portland/sand mix. I just looked at their specs and they call it masonry cement not portland. But they do have a portland and concrete sand blend called "Sand Mix" that sounds like it is closer to what you describe. I have only used the mortar on one small section so far... should I leave it or re-do it?
Flagstone: It is call Pennsylvania full color flagstone. Does that help identify it?
Thanks
-Sean
There are masons setting bluestone patio all around the house I'm working on. Their mortar is sand and portland, sand in a big pile and the cement in sacks. I can ask for the specifics if you want. They are using the well water onsite which is a little salty, as I understand it, but the head honcho is a long time mason here and I'm sure he's done it before. The tilesetter imported his own town water, but he needed a lot less of it. They are setting over 6" slabs, but they're installing what I think they intend as a fracture membrane over the slabs first... looks like Laticrete 9235, which is actually more of a waterproofing but apparently also has some anti-fracture function, although Blue 92 might be better (and way more work). They are using tile grout from sacks, and they have a nifty machine that sponges the grout off--looks a little like a lawnmover with a big rotating sponge and a water bath.
I think the thing I'd be concerned about most is the anti-fracture issue. Sounds like you've already started, but you need to be aware that the stone will crack where the concrete does. There are good products out there to minimize this (not prevent entirely), which might be worth some research.
Thanks for the reply... any info that you can get would be appreciated. I wonder if the anti-fracture layer is for colder climates? How much rebar do they have in the slab that they poured? I may have overdone it here but I was trying to prevent cracking that way. I was also assuming that when the cement separates it would force a grout joint to give not the stone.
I would like to know more about what they are using through each step. Are they grouting the stone with the same portland-sand mix that they are using for underlayment?
Thanks again!
-sean
I'd redo the area that was has the "mortar mix" as it is porous and will absorb moisture and freeze spall.
Sand mix by sakrete is packaged with the minimum amount of portland...it needs to be enriched...so buy straight portland to add. The portland/sand mix is not as porous and will resist freeze spall cycles.
Locally, "Flagstone" is sandstone with a thickness of 3-5 inches and dimension up to 3 ft x 5 ft. Your Penn Flags we locally refer to it as Penn, Blue stone comes in smaller pieces and considerably less weight per piece,
Our flagstone is normally set in a gravel/sand base...but blue stone is frequently set with portland/sand.
A Diamond blade and bushing hammer will allow you to make cuts on pieces for that "last piece" fit on each section and on the riser/kickers.
Most blue stone is compact enough that 1-1/2 to-3 inch thicknesses would be fine as nosed step treads.
When you grout/infill be sure to allow for drainage as not to trap water on the steps grout lines ...as it will be a winter hazard and contribute to the demise of the stepping stones.
...............Iron Helix
Thanks for all the great info...
How much portland should be added to the 60lb sand mix?
I plan to do the treads in one piece if possible as to avoid mortar joints there. That does raise one final question... The stoneyard wants to sell me burnt Bluestone treads. They said these stones are machined flat and have been torch treated on the edges to give it that nicely broken look. They also claim that this makes the stone harder and less likely to break on the tread's edge.
The first problem is that this stuff costs $15-20 sq/ft. Probably 5x what normal flag costs. The flag for the stair treads will cost more than the flag for the entire rest of the job.
Second, I want the treads to look like the other stones and the bluestone won't quite match the PA full color that I want to use. And it looks more formal.
Third, I don't want the surface of the tread to be dead flat... I don't want it to get slippery. The natural PA flag is flat with a nice texture to it.
Do you know anything about how this torch treatment is done? I cannot find any resources on how this is done. I have played with different breaking techniques and I am reasonably happy with a double scored piece but it isn't as nice as the edge that they get.
Thanks again.
-Sean
Sean
I meant to respond to you the other day. You have gotten good advice so far.
I've attached a picture of my front porch and steps that my mason did last spring. I couldn't stomach the cost of those bluestone treads and the thickness caused a few problems with stair rise. So we cut stones from regular flag and it looks fine. I had a few come loose, I just epoxied them down and they haven't had a problem since.
My mason mixed his mortar onsite using sand and bagged portland cement. He grouted the joints with a grout bag (I also colored the mortar that he grouted with).
BTW, I didn't use the PA full color flagstone, I got a 50/50 mixture of PA select blue and select plum. I didn't care much for the rust colored stones, but that is just personal preference. It raised the cost by 20% or something.
MERC.
The porch looks really nice... I am curious as to what the edges on your treads looks like. Is it a sawn look? or did they break the stones? For your application which looks kind of tailored, the sawn edge may fit in. For my application, I am going with natural colors (browns, greens and a bit of the lilac), natural pieces (broken), I was thinking that my treads should not look like they were sawn.
I played with a few ways of breaking them to make them look natural and it is really hard to be consistent. I was hoping that I could find out more about the "torch" treatment that I heard about.
Epoxy: What kind of epoxy did you use? And this was after they had already come loose? I would hate to be the person to find the first loose one. :-)
Steps coming loose is definitely a fear of mine which is why I was considering putting them under the risers. Everyone says not to, but I don't know why... Is it for maintenance later? Easy to replace if they break?
Thanks for the reply and pic.
-Sean
I don't know anything about the torch stuff, but it sounds plausible. If the stone yard is reputable, they probably aren't bsing you.
I used a water proof epoxy (4 minute cure - move quick). When the stones came loose, they really didn't move much at all. It was a very faint sound when you stepped on them. I think that sort of thing is expected with natural stonework. If you want flat and perfect, then stamp some concrete. I would keep the stones on top if possible. If they come loose, you can easily pull them and epoxy them. The bed will be perfectly suited to fit the stone. I just cleaned it with a hose and then let it dry in the sun for a while. Epoxy, done. No big deal.
Also I would recommend that you at least look into coloring your grout. I with a color to match the plum stones. I think it looks pretty good.
The edge of the treads are sawn square. They have faint saw marks on them, but you have to be looking for them to notice. I was worried about the whole thing before we did it, but now that I have lived with it, I think it looks good (I don't always say this about things I do). I'd do it again (and keep my $600 or so I saved by skipping the full size treads). If you don't like the sawn look, there are ways to break the edges so they look more natural. I don't have skill in that, but my mason showed me how they produce the scalloped edge on the big treads.
Another tidbit that may not have been answered -- I had a 1" overhang on the step flagging.
MERC