We are relandscaping our back yard in Portland, Oregon with flagstone. We hired a contractor to excavate and create a base, but I believe the depth of the excavation may be insufficient. Throughout most of the yard they laid several inches of crushed rock as a base plus there is room for about 4 inches for sand and flagstone. That part seems fine. But where the yard abuts the driveway, they only excavated about two inches. There is one inch of rock and room for an inch-thick layer of flagstone, with no room for sand. If we put inch-thick flagstone on an inch of gravel, won’t the flagstone just break?
Thank you!
MichaelW
Replies
Not a mason.
Slightly confused by the post - is there already stone next to the driveway? or just a 2" deep hole?
If stone already there - Is the stone just loose gravel / crushed stone or is it "crush and run" (crushed stone of many different sizes with many fines included)? Crush and run packs very well and would support the flagstone to prevent breakage, although 1" sounds pretty thin.
Jim
Never underestimate the value of a sharp pencil or good light.
Thanks. You read my post correctly, they dug out a depth of two inches next to the driveway and then put in one inch of crushed rock, leaving an inch of clearance for the flagstone. I don't know what kind of rock it is. It looks like dirty gravel.
Why did you just hire a crew to do the base?
Who's doing the stone? Why can't that person(s) do the whole thing?
It's more of a drainage issue rather than one of the flagstone breaking. Water can still pond in 1" of gravel. If you're in a place where freezing occurs, this might heave your stone out of place.
As someone else said, the gravel can be fine by itself. We have pavers over 4"-6" of compacted gravel (no sand), and they've stayed level and locked in place for a several years now.
Same here, I'd have at least 4" of crushed gravel and probably more. We'd first remove ALL the topsoil, which is generally about a foot. Lower lifts of gravel would be 2" minus, the top inch of gravel would be 5/8" minus, all compacted with a plate compactor.
The winters are pretty mild here. We get some snow and freezing weather, but not a lot. When they excavated, they did put in a slope generally away from the driveway and house. They compacted the gravel base with a mechanical compactor.
We have the stone all laid out and ready to be set and don't want to have to redo the dig if we don't have to.
What is under the gravel base in the areas where it's only an inch thick?
Just soil. There was concrete and raised beds in this location before we excavated.
What does the contract say -- how thick is the base supposed to be? I like a minimum of 4" compacted base; and, inch of stone dust (I try to stay away from sand alone as it tends to wash away - unless you mix dry with cement) Need the best base you can get as that is the foundation.