Patio Subgrade
In our small backyard, we plan on laying down a roughly 15’x15′ bluestone patio. Our contractor has given us two options for a subgrade: 1) Dry well and sand base 2) 12″ gravel subgrade and sand base Given that this is for a low-traffic/weight patio, is the full gravel subgrade really necessary or is the…
In our small backyard, we plan on laying down a roughly 15’x15′ bluestone patio. Our contractor has given us two options for a subgrade:
1) Dry well and sand base
2) 12″ gravel subgrade and sand base
Given that this is for a low-traffic/weight patio, is the full gravel subgrade really necessary or is the sand base sufficient? The soil is a blend of dirt, construction debris and clay. We only see minor puddling during heavier rainstorms.
What are the risks with going with just the sand base?
We’d prefer not having to re-level the stones after every winter…
I had the area in front of my brownstone paved with random-sized bluestone on a sand base with landscape cloth under the stone. It’s been fine for three years now.
In response to Steve. I think you’re getting a mortar base mixed up with a concrete base. You cannot have four inches of mortar eg lime and cement. It will crack.
Disadvantage for the solid base is that any water that gets below the slate will have no where to go. when it turns to ice in winter you could end up with lifting.
A 4-8″ bed of gravel or stone is important for drainage.
Another option is a mortar base, which is what I have here. There’s a compacted layer of dessicated stone and a 4″ mortar bed laid pretty much the same as the mud base for a tiled floor. It’s the most stable base for pavers but it has to be pitched for drainage.
Thanks for the info.
Definitely a gravel base. The most important thing is that the gravel is compacted with a compacter, as is the sand. Also make sure he puts a landscape fabric between the stone and sand to prevent weeds from growing up. Having said that 12 inches of sub base seems alot. It’s usually about four inches of gravel and two of sand.
Go with the gravel. We have one part that’s a gravel base and one part sand base (we had the contractor extend something that was done because we had extra paving stones). The part with just sand has more weeds, ants growing in sand, etc. I also think it will require releveling much sooner (it’s only a year old).