Using Pebbles to Extend Patio

Sammy1980February 27, 2012

My wife and I recently fenced in our backyard and we ended up with this "nook" area that measures 16'x7'.

Here's a picture of the area I�m talking about.

We would like to convert that area into useful space that we can maybe use for our BBQ grill and our fire pit. Our plan is to level that area out then backfill it with pebbles and use some pavers to support the BBQ grill and fire pit.

The first thing we did was built a short retaining wall close to the fence so that when we level that dirt we don�t end up burying any part of the fence. We also didn�t want to apply too much force on the fence directly when we level the area.

Our next step will be to level that clay soil the best we can then top it off with 2" of smooth river pebbles.

Then we will lay down about 12 pavers for the grill and 4 pavers for the fire pit and finally add 1 more inch of pebbles to level everything out with the existing patio. I hope I'm describing our plan clearly; we�re both very new to landscaping projects.

I was hoping to get some feedback people with more landscaping experience to make sure we're not missing anything.

1. Is this a bad plan? Did we miss anything?

2. Are 2-3 inches of pebbles enough if someone were to walk on the area?

3. Are 2-3 inches of pebbles enough if someone were to set a chair out there? Wouldn't a chair leg just sink in?

4. Would you lay down a weed barrier on the dirt before you start adding the pebbles?

5. Would you use any sand to make it even more level before you start adding pebbles?

6. Would a certain type of pebble or rock make this a better project?

Thanks so much guys.

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I posted your pics directly. (To do that obtain html code from the photo hosting site and paste it directly into your message here.)

    Bookmark   February 27, 2012 at 4:49PM
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The part of the plan that's bad is because of the pebbles. They are HORRIBLE to walk on because they "squish" and scatter. You must use an aggregate that packs down would be a mixture of particle sizes using angular pieces... none probably not larger than 3/8" and then all the way down to sand size. Examples would be crushed brick or oyster shells, decomposed granite... things like that. If right material is used, packed hard, a chair leg will not go through. I would suggest 3 1/2" - 4" thickness layer. Would not bother with additional sand below. Not needed. But you need edge restraint or the aggregate will migrate away and cause eventual failure. (You could put down layer of polypropylene landscape fabric to separate soil from aggregate. It gives it more stability. But as a weed barrier... I've never seen a weed barrier actually work for any length of time. The reason is because there is always soil "washing" in on top of it and that will support weeds.)

For such a small area I'd be more inclined to do the whole thing out of pavers (not patio blocks) on a base of crusher run and 1" sand setting bed. The finished result would be much tidier and without any of the aggregate mess (scatter and tracking in.)

    Bookmark   February 27, 2012 at 5:26PM
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deviant-deziner(Oh zone)

1. Is this a bad plan? Did we miss anything? - I might be concerned with a flame from the fire pit if it was any where near your wood fence. Perhaps a piece of core ten to deflect the flame and heat . You might like to see some of the inventive fire sculpture ideas using core ten by Jay Griffith or Rob Steiner .

2. Are 2-3 inches of pebbles enough if someone were to walk on the area?
All pebbles are not created equal. Round pebbles are somewhat comfy to walk on bare foot but do not compact well. Angular pebbles compact well but are unpleasant to walk on bare foot. Either type of pebble benefits from a proper stable sub base to stablize the top layer of pebbles.

3. Are 2-3 inches of pebbles enough if someone were to set a chair out there? Wouldn't a chair leg just sink in? - 2 to 3 inches of pebbles is fine , but it really makes a difference in the type of pebbles that you use. Round pebbles will slide away from one another to let a chair leg settle. Angular compacted pebbles with a proper base will support a chair leg.

4. Would you lay down a weed barrier on the dirt before you start adding the pebbles? We do. We use a double bonded weed barrier cloth, it is the same type of professional cloth that the dept. of transport uses when laying down an asphalt road. We lay it down on the compacted soil. Then place ( depending on region and soil profile ) 2 - 3 inches of compacted road base and top that off with 2 inches of gravel.

5. Would you use any sand to make it even more level before you start adding pebbles? Sand is a great leveling tool. It is helpful in setting loose stone or pavers.

6. Would a certain type of pebble or rock make this a better project? - Identify your needs and how you plan to use the area. That will inform you to the right decision/ materials choice for your specific project.

    Bookmark   February 27, 2012 at 9:37PM
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Thanks so much for the detailed replies guys.

Here's a more complete picture of what we're trying to do. We already have a pretty decent sized patio as you see in the picture below. The area to the left of that patio is the area that got enclosed in the fence.

I guess the main purpose we had in mind for it was just a little extra space to move the fire pit and the grill off the patio so we have more room on the patio for an outside couch.

The pavers idea sounds cool but we're worried it would be too much work and we figured we can get away with the pebble idea and just a few pavers to support the grill and the fire pit.

    Bookmark   February 28, 2012 at 8:19AM
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Seeing your grill and firepit gives a better idea of what you're trying to accomplish. I think extending the patio with aggregate material will work out fine for you. Calling it "pebbles"... which sounds "clean" and of uniform size has me thinking you're envisioning the wrong kind of material to build it of. I'm including a link below that shows some samples of the types of material that would work well. Notice that each is made of little chips, smaller chips, angular sand and dust. It's the combination of sizes that allow it to pack down tightly, as each little particle settles (fits) in closely to the other particles. (This is not possible with "clean," uniform size material.) Even though an individual particle of aggregate is angular, the top surface of the whole compacted area, because of the way each particle fits together (and that none is particularly large) is flat and smooth.

When "weed barrier" is placed above the compacted soil (or subgrade) before placing aggregate material, it's function is not as a weed barrier, but as a soil separator and stabilizer... which is the good way to use this material. ("Weed barrier" fabric that is made of rubber-like material or is stretchy will not work for this.) Imagine a stone on top a wet, saturated ground. It would be pretty easy to put some weight on that stone and push it down into the mud. But if there was a piece of tough, non-sretchy fabric between the ground and the stone... providing that the fabric didn't "give," it would be about impossible to push the stone into the soil. What "holds" the fabric and prevents it from "giving" is that you are putting down AN ENTIRE COMPACTED LAYER of heavy material on top of it. Then, pressure applied to one small spot of the aggregate "paved" area will be resistant to deforming. Given that the area you are constructing is quite small and the fact that it's for light duty, would incline me to think that stabilizer fabric is optional, not critical. (It would be pretty easy to top dress any depressions that formed over the life of area.)

The most important considerations are the aggregate you choose and it's thickness (min. 3",) the edge restraint and compaction of the layers. Manual compaction would work OK for this small project.

Crushed brick (as long as it contains "fines") is another material that would work for this project...

Here is a link that might be useful: Path and trail aggregate materials

    Bookmark   February 28, 2012 at 10:22AM
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Yardvaark, I can not thank you enough!

That stuff looks 10 times better than generic river pebbles and it makes me feel better about being able to pack down enough to withstand someone walking on it or the occasional chair. It almost sounds like I can even get away with packing this stuff down and not using pavers to support the fire pit or the grill, what do you think?

Is that stuff in the same price range as river pebbles? I need to call around to see if anyone even sells that stuff here, I've never seen it before. We both love the recycled "Fire Brick Blend"!

    Bookmark   February 28, 2012 at 11:09AM
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You'll have to explore locally to see if crushed brick is available. Start by calling someone who manufactures or distributes brick and they may be able to give you a lead. (It's usually used for sports facilities.) While that web page I showed includes numerous samples of trail and path material, more likely than not, only a few will be available in a given locality. Best thing is to make a visit to landscape supply yards in your area that stock bulk material and see what they have. (I live in a small town and even the supplier here has a display "garden" with all their various materials laid out. You can even walk on them.)

Most aggregates will cost similar to others. But this will encompass a range, not a single price. Check your local prices to get an idea of what things cost. At a 3" thick layer, you need about 1 cubic yard of material.

    Bookmark   February 28, 2012 at 11:25AM
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I called 7 landscaping supply stores in Birmingham Alabama and most of them have never even heard of decomposed granite. I'm gonna have to do a little more digging.

Can you think of substitutes that would have that kind of "compactability" and still look decorative. A lot of the stores I called suggested crushed limestone but that doesn't look as pretty.

    Bookmark   February 28, 2012 at 11:39AM
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That's the problem with different localities and that's why it's best to actually pay a visit to the landscape supply yard. I notice that Bedrock Landscape Supply has "crushed red rock" so that may be an option. But it's best to go see now that you have an idea of what it is you're looking for. I'd visit two or three places if it's not inconvenient. It's possible they carry slightly different variety of materials.

    Bookmark   February 28, 2012 at 11:56AM
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karinl(BC Z8)

Going downhill to a fence is a brutal set-up - I have such an area too. Besides the issue of weight against the fence that you have already thought of, the problem is that anything you put against the fence will begin to rot it. Your retaining wall is a bearable solution but has the disadvantage that dirt, leaves, and weed seeds can eventually settle in there and both rot the fence and create a population of weeds that is difficult to eradicate (you can't get your hand in there to pull). Also good spider or slug habitat, if that matters to you.

If you had it to do again, the best method would be to build a small concrete retaining wall level with your patio and put the fence on top of that. Since that didn't get done, I wonder if you could retrofit a solution.

The fact that your fenceboards appear to touch the ground is already a bit of a problem - this will rot them faster. So if you could either move the boards up to get them off the ground or cut them off above ground, that would be a start. As for retaining the stone you plan to put down, it depends on whether you have space outside the fence that is still yours, and how much height you can create. You might be able to set in some long stone pieces and shore them up a bit from outside. Or, just raising your fence bottom above the retaining wall that you've placed will allow you to weed from the outside, and I would put a row of pavers outside your wall to limit weed growth and to enable your neighbour to mow as close as possible.

About the decomposed granite... it may go by another name in your area. I've never heard the term around here.
I think Yardvaark means the stuff that is often packed down under a patio, under the sand. So it might be described as granite crush or granular base layer material... describe what you're after, or better yet as Yardvaark suggested go to the landscape yard and look.

Karin L

    Bookmark   February 28, 2012 at 2:22PM
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Karin our plan was to backfill that cavity between the retaining wall and the fence with 57 stone to help with drainage and to discourage weeds and spiders from settling in. I already started lowering the ground around the areas where the fence touches the ground to help prevent rot and to make it easier to weedeat under the fence.

I think my wife and I are gonna have to spend a few hours Saturday visiting landscaping supply stores to see what we can find. One place sounded a little promising, they said they had crushed red rock and crushed "brown run". She said it looked like pea gravel in color but it was much easier to compact. We're gonna go check it out.

    Bookmark   February 28, 2012 at 3:08PM
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