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i am building a bluestone patio with a freestanding /part retaining stone wall around it. i put about a foot of gravel under the wall and large rocks as a base. about 2 feet is under ground. built up about 18 inches of wall above ground. now i need to fill with something to bring the patio area up to grade. after patio is down, i want to build about another 18 inches of wall to surround the patio. we have a deep frost line here. do i need to use gravel to fill, or would any fill work? any tips would be appreciated.
ericalynne, is your question about the process of building or laying 'the floor' of your patio using the dryset method? (as opposed to pouring concrete)
i am using the dry set method. i am not pouring concrete. my main concern is having enough drainge under the stones. we have heavy clay soil and with our winters i don't want to have to redo it every year.
If I understand this correctly, you need to bring the patio up 18" to meet the wall you have built, right?
You could get away with busted up concrete or 'rip-rap' stone to fill most of it, then the gravel on top. You have an opportunity to put drain pipes under this now, too. Obviously, make sure they run downhill. There's no such thing as too much drainage under this stuff, as long as it's compacted well.
"do i need to use gravel to fill, or would any fill work? any tips would be appreciated.'.
A fast draining inorganic fill such as 3/4 inch gravel will do the trick.
Basically you don't want to back fill with anything that is going to decompose and shrink.
We use a local 3/4" gray gravel quarried from a granite quarry and it meets with our local code compliance.
Below is a photo of a raised terrace that was back filled with compacted 3/4" gravel with a grid pattern of 4" diameter perforated and closed pipe drainage system.
We poured a stem wall around the perimeter of the terrace ( it looked like a big bathtub) , wrapped and laid in our drain pipe to the correct horizonal slopes, made our connections and then back filled with 3/4 inch gravel.
Ontop of the gravel a 4 inch reinforced concrete slab was poured and then we mortared on the slate.
In your case you would lay a filter barrier down ontop of your compacted gravel base, sift your setting bed of sand and then set your blue stone slabs.
The filter barrier keeps the 'setting' bed of sand from sifting down into the gravel over years of rain, freeze thaw and just plain old use. It is a good idea to use if you are using coarse angular gravel that may not pack down completely hard yet permeable.
I have a well worn saying " Drainage is the bane of my existance ".
If anyone is going to accuse me of being conservative to overly conservative in my professional life ( certainly not my personal life!)
, it is that I do have the propensity of over engineering the drainage systems on our projects.
There is nothing better than sitting in your office during a week long torrential downpour and not have the phone ring about drainage issues. ( which happen this last past year where we recieved 24 straight days of rain in which one day we received 7 inches in less than 20 hours )
Conversely so, there are few things worse in life than going out to a job to fix a drainage problem in the pouring rain and muddy slippery soil.
The project above was done about 10- 12 years ago.
went to the "stone store" this AM and picked out stone for the pathway in the front yard. They suggested that we use 'decomposed granite for the base and filler(grout). Said it compacts and tamps itself. We lay 2 " of the dec. granite and set the flat stone on top and arrange how we want it and go to the next stone. We hose it down and fill the between spaces w/ more dec. granite and hose down. The rain in turn will help the securing process.
