Bricks, Masonry, Asphalt and Concrete - laying Flagstone
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03-14-00, 10:01 AM
Hi again, now I'm trying to lay flagstone on an existing cement pad. I'm using Bouquet Canyon stone - Do I need to make them about the same height or can I adjust by putting more or less morter underneath? Second, Do I put a bed of morter on slab and also "butter" the entire bottom of the stone? Third, is placement simply how I think it looks or is there a rule of thumb for big and small - I'm not sure how random to be? Fourth, Can I lay part of slab or should I do it all at once? Thanks in advance for your help again, but this is really interesting to learn. I did not ever imagine that this stone work was so exacting and complex, but it seems to be if you want to do it right. Thanks again!
03-14-00, 10:40 PM
No one can accuse you of being lazy.
Q. Can I lay part of slab or should I do it all at once?
A. You can start and stop as the need or whim arises.
Q. Do I put a bed of mortar on slab and also "butter" the entire bottom of the stone?
A. The mortar goes on to a pre-dampened slab. The stone is set "clean and dry".
Details:
The day before wet the slab using a slow soak, then allow surface moisture to disappear before laying. Burlap bags, old sheets or blankets will help. Do not lay while surface water is present.
The mortar for stone is 1 part Portland Cement to 3 parts masonry sand. Lime is not used! It is a more difficult mortar to work with and it's mixed much stiffer than brick or block mortar. Stiffness ranges from just beyond binding together (appears like a slightly crumbly mass) to a mass that will hold its shape when squeezed in the hand. For lighter weight stone the mix would approach that of a mortar that is slightly too stiff for block.
The grout for the joints has the same proportions, but 1/2 part fireclay may be added to add some bulk and improve workability. Grout 24 to 48 hours after laying, using a mortar with the consistency of near that of block mortar.
Adjust both mortar and grout consistency to suit the need!
Q. Do I need to make them about the same height or can I adjust by putting more or less mortar underneath?
A. Make them all the same height, leveling and positioning each one as you go.
Details:
The mortar bed should range from 1" to 1 1/2". When the stone is set the bed will compress 1/4" or more. Adjusting the mortar bed to the stone is normal, but there are limits. (Do not use a 2 1/2" bed under one stone and a 3/4" bed under the adjoining stone. If necessary cleave/cut the stone or knock of highs).
The stone is lowered straight down gently, setting the edges of the stone on wooden wedges if necessary (they are withdrawn as necessary for leveling and may be left in place and withdrawn later then the holes packed mortar), into the bed of mortar. Avoid twisting into position. If necessary pull the stone, clean off all the mortar and discard it, then start all over again. Do not reuse compressed mortar.
Once the stone is set, use a rubber or wooden mallet to level, and use a level and a straight edge over a distance. There should be no need warn people to watch out for certain stones, count steps before a hazard, ect.. Highs on the stone should be dressed flat, and divots in the stone should be on the bed side or the surface dressed flat.
Q. Is placement simply how I think it looks or is there a rule of thumb for big and small - I'm not sure how random to be?
A. There are no exact rules but the following might be a helpful guide.
Details:
Placement is pleasing to the eye plus considering a 26" to 30" walking stride, which is an average for most people. It is a poor practice to place a small stone right in the middle of the stride path without a very smooth transition to the adjoining stones. Likewise, people should not have to "hop scotch" or adjust their stride noticeable while walking.
When large and small stones are mixed in a random pattern, I think that you'll find that using no more than two smaller stones to span a larger three or four stone sided stone on no more than two of its sides is more pleasing to the eye. (No doubt, stones will cut and trimmed to fit). Also, when larger stones are spanned, try to offset the joints from the middle of the larger stone by using a smaller stone and a slightly larger one, so you don't wind up a "regular pattern" mixed in with an irregular one. Finally, mix things up. Avoid using all of the larger stones to gain distance, only to fill one end with small left overs.
The mortar joint spacing should be relatively equal. Relatively equal doesn't mean a fitted appearance, but it does mean no wide run-outs mixed with narrow joints. The joints are adjusted to suit the width of the walkway and the size of the stone, plus a minimum spacing rather than a maximum spacing is used. (Yup, this uses more stone, plus there will be cutting and waste). The more exposed mortar that exists, the more chance of moisture damage later on.
To trim a stone for fit: lay one edge over the adjoining stone, trace a pencil line, lay the stone over a 2x4, score the line deeply with a chisel (working back and fourth across the stone, slightly deeper each time), then snap it with a stone hammer (gently along the line) or use a hammer and brick set.
Q. Can I lay part of slab or should I do it all at once?
A. You can start and stop as the need or whim arises.
Q. Do I put a bed of mortar on slab and also "butter" the entire bottom of the stone?
A. The mortar goes on to a pre-dampened slab. The stone is set "clean and dry".
Details:
The day before wet the slab using a slow soak, then allow surface moisture to disappear before laying. Burlap bags, old sheets or blankets will help. Do not lay while surface water is present.
The mortar for stone is 1 part Portland Cement to 3 parts masonry sand. Lime is not used! It is a more difficult mortar to work with and it's mixed much stiffer than brick or block mortar. Stiffness ranges from just beyond binding together (appears like a slightly crumbly mass) to a mass that will hold its shape when squeezed in the hand. For lighter weight stone the mix would approach that of a mortar that is slightly too stiff for block.
The grout for the joints has the same proportions, but 1/2 part fireclay may be added to add some bulk and improve workability. Grout 24 to 48 hours after laying, using a mortar with the consistency of near that of block mortar.
Adjust both mortar and grout consistency to suit the need!
Q. Do I need to make them about the same height or can I adjust by putting more or less mortar underneath?
A. Make them all the same height, leveling and positioning each one as you go.
Details:
The mortar bed should range from 1" to 1 1/2". When the stone is set the bed will compress 1/4" or more. Adjusting the mortar bed to the stone is normal, but there are limits. (Do not use a 2 1/2" bed under one stone and a 3/4" bed under the adjoining stone. If necessary cleave/cut the stone or knock of highs).
The stone is lowered straight down gently, setting the edges of the stone on wooden wedges if necessary (they are withdrawn as necessary for leveling and may be left in place and withdrawn later then the holes packed mortar), into the bed of mortar. Avoid twisting into position. If necessary pull the stone, clean off all the mortar and discard it, then start all over again. Do not reuse compressed mortar.
Once the stone is set, use a rubber or wooden mallet to level, and use a level and a straight edge over a distance. There should be no need warn people to watch out for certain stones, count steps before a hazard, ect.. Highs on the stone should be dressed flat, and divots in the stone should be on the bed side or the surface dressed flat.
Q. Is placement simply how I think it looks or is there a rule of thumb for big and small - I'm not sure how random to be?
A. There are no exact rules but the following might be a helpful guide.
Details:
Placement is pleasing to the eye plus considering a 26" to 30" walking stride, which is an average for most people. It is a poor practice to place a small stone right in the middle of the stride path without a very smooth transition to the adjoining stones. Likewise, people should not have to "hop scotch" or adjust their stride noticeable while walking.
When large and small stones are mixed in a random pattern, I think that you'll find that using no more than two smaller stones to span a larger three or four stone sided stone on no more than two of its sides is more pleasing to the eye. (No doubt, stones will cut and trimmed to fit). Also, when larger stones are spanned, try to offset the joints from the middle of the larger stone by using a smaller stone and a slightly larger one, so you don't wind up a "regular pattern" mixed in with an irregular one. Finally, mix things up. Avoid using all of the larger stones to gain distance, only to fill one end with small left overs.
The mortar joint spacing should be relatively equal. Relatively equal doesn't mean a fitted appearance, but it does mean no wide run-outs mixed with narrow joints. The joints are adjusted to suit the width of the walkway and the size of the stone, plus a minimum spacing rather than a maximum spacing is used. (Yup, this uses more stone, plus there will be cutting and waste). The more exposed mortar that exists, the more chance of moisture damage later on.
To trim a stone for fit: lay one edge over the adjoining stone, trace a pencil line, lay the stone over a 2x4, score the line deeply with a chisel (working back and fourth across the stone, slightly deeper each time), then snap it with a stone hammer (gently along the line) or use a hammer and brick set.