2

I need to regrade my patio and I had a quick look under the pavers to see how it was built. To my surprise I found the following layers:

  • one thin layer off gravel -you would say it is about 1/4in thin
  • weed barrier
  • 4" crushed limestone
  • precast brick pavers

I expected something more like 4" of gravel and 1" of sand + pavers on top (like it is described here : http://www.homedepot.ca/know-how/projects0/laying-out-and-digging-a-patio )

I think that the whole thing is too little permeable to water, and it drains more difficultly and that correlated with a slope toward the house is giving me a wet wall ... I need to raise the level of the patio with 1"-2" in order to make it drain away of the house

Now the question is: do I add sand over the existing limestone crush or I buy more limestone crush ?

From drainage perspective, is it normal to have mostly just this limestone crash layer and nothing else? Will this crushed limestone trap the water longer than it should?

  • Do you want to keep the bricks or to pour concrete slab? Do you want to be able to remove paving (are there any pipes or something like that under which should be accessible) – python starter Jun 2 '15 at 7:44
  • It is a precast concrete brick patioit will stay so. I want to be able to correct any settled area later. I do not want to pour concrete. – MiniMe Jun 2 '15 at 11:11
  • FYI, patios (well, most, at least) aren't designed to be permeable at all. They are designed to be properly sloped for run-off. The problem with this install isn't so much the underlayment as it is the slope in general. – DA01 Dec 29 '15 at 20:39
1

I wouldn't call that a typical base, but if it was properly compacted, it should work. The typical base is pretty much what you described:

  • topsoil dug down to undisturbed soil and/or topsoil dug out then soil machine compacted
  • 2" layer of crushed rock, machine compacted
  • 2" another layer of crushed rock, machine compacted
  • repeat until you get to 4" or the desired height (if above 4")
  • 1" sand, leveled
  • pavers

Note that in this system, you're not designing for permeability or drainage at all. If you are using pavers, this is hardscaping, and is meant to shed water, not absorb it. To properly shed, it needs to be properly sloped. This is true for the base layer as well.

The purpose of the base layer is to create a solid, stable surface. Ability to drain is desirable (to avoid frost heave) but that's secondary to providing a proper surface to shed water.

In your case, it sounds like you already have 4" of compatible material. I'd do the following:

  1. remove pavers
  2. rent a compactor and compact existing base
  3. add additional base material and compact to get the slope you want
  4. add sand
  5. put pavers back
  6. add locking sand to joints

the big catch here is that this will ultimately raise your patio next to your house several inches. If that's tolerable, you're good to go. If not, then you have to do the reverse...instead of adding material closer to the house, you need to take material and remove it further away from the house. This will reduce your total base at the outside edges, though. That may be acceptable in your case.

0

OK, now this is what I would suggest you to do (and what has proven to be the best solution according to my experience): Of course first take everything out. Be careful when you remove bricks not to damage them, and where you put them. Remove everything up to last layer of gravel. Add more gravel so that total thickness of this layer is round 4 inches. When I say 4 inches I mean hardly compacted; that is also very important: you must compact this layer really good. My advice is to use specialized vibrating equipment. Now comes the part which you will most likely disagree but, once again, according to my experience it is the only long term solution: pour thin concrete slab (round 3 inches, maybe little more) and reinforce it with some thin mash. This creates rock solid layer for your bricks, and guarantees that it will stay flat, without any bumps or settling for a very long time. Next step would be to make fine sand bed. Its only purpose is to fill gaps between bricks and to make them stand vertical. Now you can put again your bricks and that's it. In case you want to fill in the gaps between bricks (fugues) you can fill them with extra fine sand, or with some mortar. I know this sounds complicated but for a rather small area like patio I would highly recommend that you do it this way. If you have any questions feel free to ask.

  • I just need to understand why the gravel is missing and if this is OK. The other thing that I want to understand is if I can add more limestone crash instead of adding sand. Fine sand will be used to fill in between pavers to lock them in. I am thinking of acrylic sand just to avoid any water problems from now on. I do not have the time and the resources to do what you suggested – MiniMe Jun 2 '15 at 15:51
  • Missing gravel is not the good thing. Gravel is being used in order to make the base more stable, harder so that the paving wouldn't sink. I think that the sand makes better bed than the limestone, plus limestone likes to soak water. When it comes to waterproofing I have never used acrylic sand; but to tell you the truth I have never had water related problem when the preparation (compacted gravel) was done properly. Maybe you can look for some specialized product similar to the once being used for ceramic tiles. – python starter Jun 3 '15 at 8:04
  • I was under the impression that the limestone is a coarser material than sand and for that reason it will let the water pass through easier than sand. As far as the absence gravel goes that is a fact and I can not fix it. The patio has bees stable for most of its area excepting a couple of spots where in fact I believe that the water helped the settling – MiniMe Jun 3 '15 at 11:31
  • Like I said, I have always used sand and I only recommend medicines which I have tasted :).Absence of gravel is solvable: you just add, it since you are planning renovation. And settling usually does not appear everywhere, well eventually it does but it starts locally. – python starter Jun 4 '15 at 7:38
  • If you don't want to compact manually, but also don't want to pay to rent a compactor, you can make a compactor yourself by mounting an old air conditioner motor on a TV tray, and putting a 5-10 pound weight lifter's weight on the half inch motor shaft. Put something on the end of the shaft to keep the weight from coming of, but leave plenty of room to wiggle. The thing vibrates like mad, and my gravel and sand patio has be stable as rock for 8 years now. I did take the time to ensure the final slope of the sand was away from the house. – Wayfaring Stranger Dec 29 '15 at 19:07

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.