This concrete porch in Ayr we dressed it up with natural stone flagstone square cut in the middle with natural stone caps at the edges as well as natural stone cladding along the sides. When we start a project like this we always clean off the porch because especially around the edges we’re going to be adhering those natural stone caps using a Hardscape adhesive to the concrete.
Now there are a couple of ways that we can do this install when we overlay an existing concrete porch. We can wet lay them meaning we use a Type S mortar mix to then adhere all the Natural Stone to the porch. I don’t like doing this because in our Winters that we get as well as using deicing Solutions it can quickly deteriorate that Type S mortar mix especially in the joints. Additionally doing so is a pain to have to tear out if you have to do so in the future when that deterioration happens.
Instead what we like to do is install our natural stone caps along the edges and then lay a non-woven textile in the interior with some HPB (High Performance Bedding / 1/4″ clean crushed chip) or some concrete sand. We then lay the natural stone flagstone on top of this leveling it out with a slight slope away just in case any water does get on this covered porch area we want it to move out of the system. What does HPB or concrete sand does is it allows any water that does get into the system to move down through it because it is drainable and out of our system following the pitch of the concrete porch.
When we lay out our caps we want to make sure that we have equal spacing throughout the project so we measure our caps lengths and we measure the distance between two thresholds in this case between our two brick pillars. We could lay a 4 ft stone cap followed by say a 3 ft natural stone but it would look awkward having a non-symmetrical front entrance because you do somewhat see that scene. Instead what we do is cut two three and a half foot pieces out of our 4-ft caps all those so that it is nice and symmetrical between those two brick pillars.
We then adhere those caps using a hardscape adhesive and it is important that we use perpendicular beads to the face of those caps. This allows any water that does get into that system to move its way out through the face of those caps between the concrete and the bottom of the natural stone caps. We then line up our caps with a 2 in overhang because our natural stone going on the face of that concrete porch is 1 in thick that gives us a final result of a 1 in overhang.
We can then lay our nonwoven geotextile through the area add in our HPB in this case because our caps are 2 in thick our natural Stone flagstone is 1 in thick so we have 1 in of room for HPB to go in if we do not have that one inch it’s better to use concrete sand. I like using HPB whenever I can because it is much more free draining than concrete sand is.
I like to lay full pieces in the front entrance and hide the cut pieces along the far side of the porch. That way what you visually see are nice full slabs rather than any cuts and smaller pieces of slabs. The smaller pieces or the cuts they’re hidden away from that front entrance into the doorway. If the doorway was further to the right of this porch then we would use the same method that we did with the caps to make sure it was nice and symmetrical throughout the entire porch overlay.
Natural stone flagstone is variable in its heights. So there is an added step in making sure that this porch is level with a slight slope towards the face of those Natural Stone caps. We screed out that HPB bedding layer and make sure that we have that slope then we lay our natural Stone flagstone in the interior finish our cuts and then we go through one more time to raise or lower certain areas of that flagstone because of those variable heights.
Once we have the result that we are looking for we can then install our polymeric sand in the joints. We do this by sweeping out the polymeric sand and using a rubber mallet on each piece of the natural Stone to vibrate that sand down to the bottom of the joint consolidating it. We then blow off the surface using our leaf blower to make sure that there’s no remaining dust on the surface that would harden and discolor are natural stone and then use a shower setting on our hose to be able to activate that polymeric sand.
When doing an overlay we also want to make sure that we’re not completely covering any weep holes you can see around the edges at the very bottom of the brick there are holes in between bricks and those allow airflow in behind the bricks and we do not want to cover those preventing that airflow to happen.
This is our final result of our natural Stone flagstone porch overlay.
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