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rory_88 09-21-2010 07:47 PM

Brick Patio Help Please!
I'm hoping someone can offer some expertise as I plow through this project.

I'm installing a 10 x 12 brick patio. I inherited 500 old brick pavers with the house that must have come out of some sidewalk somewhere. They are nice bricks. Note that there are brick walkways in other parts of the yard that I am trying to match - same pavers. The walkways are retained with 6"x6" pressure treated. Also please note that I am aware that the lumber is actually 5 1/2"x5 1/2". All figures below account for that fact.

I am installing the patio in an area with a fair grade. Here is my plan (which is now partially executed).

1. Excavate to depth needed for the base layer, sand layer, and 6"x6" landscape lumber. The excavation is done. So at one end the depth is 10" to accommodate 4" of base layer + 6" of lumber. The sand layer will sit inside of the 6"x6". The far end of the patio now sits 20 1/2" below grade.

2. Install patio base stone @ 4" compacted. I am preparing to do this over the weekend.

3. Install 6 x 6 landscape lumber border.

4. Install sand base layer at 1 1/2" compact (does it need to be 2"?).

5. To deal with the grade I plan to step up the border with additional 6 x 6 lumber to create a small retainer on two sides and 1/4 of the third side in order to bring it up to the 18" grade. This will require the addition of two steps running the width of the patio. There will only be one true step as the second step will be at grade. The true step will be 6" x 15" with brick in between. I will back fill the mini retaining wall with landscape fabric and gravel so that any water drains downwards.

So my questions:

A. What issues could I face with a three tiered mini retaining wall made from 6 x 6 landscape lumber? Does it need a footing of any sort? Weep holes? Note that one of the tiers will be at grade so only two will show above grade.

B. What about water under the patio? Because this is built into a moderate slope water will flow behind the retaining wall and under the patio. Please note that this patio is 1 foot diagonal from the corner of the house - close enough that the potential for water in the basement concerns me. I installed a drywell nearby and I could run a french drain underneath the patio if needed, though I would prefer not.

C. Do I need to be concerned with heaving in the winter? I'm in Massachusetts so it gets plenty cold.

Any advice appreciated!

inspectorD 09-22-2010 05:51 PM

Sounds like you did your homework.
Make sure you pitch the patio away from the house, and make sure you remove ALL top soil(much darker)...even if it goes down 10 inches.
As always,post pictures.:)

rory_88 09-22-2010 07:01 PM

I'm the product of an architect so I dug many a ditch in my youth...

Yes, it will pitch away from the house. Top soil is all gone.

I just want to answer those questions before I go putting it all together. I'm starting to think that tying in to the drywell is the way to go... damn. Pure harassment.

I'll post up some pictures. No worries.

mudmixer 09-22-2010 08:31 PM

You compact the base material and the sand setting bed should be a uniform 1" thickness and UNCOMPACTED, but just leveled. You are not using real pavers because of the size, but many people use that term for the oversized units.

If you butt the "pavers" together, set them ine the screeded san bed. sprinkle sand over them and vibrate with a plate compactor to level the surface and draw excess sand into the joints and drive the surface sand into the joints. This surface interlock ties the surface together. This not writeen in stone, but it follows the procedure for real interlocking concrete pavers that can carry very high loads. If you have some clay pavers cracking may be a problem.

Your choice of wood is a totally different problem.


rory_88 09-22-2010 09:45 PM

Yup. I get that. Thanks for the detailed explanation.

I should have been more clear. My plan is to compact a 1/2 inch of stone dust before the border goes down. I have lots of it from removing a separate walkway and I find it easier to level than compacted stone. Then the loose stone dust screeded in place inside of the border (I'm familiar with the process).

With the loose stone dust screeded in place, bricks laid, and loose dust brushed into the joints, how far can I expect the bricks to settle when I run the plate compactor over it? 1/4 inch? 1/2 inch? I'm using good old stone dust, not sand or polymeric compound.

Can you educate me on the problems I may face with my choice of wood? This is a real area of concern for me, as this is where I have the least experience.

Any thoughts on the water issues?

Thanks for your help! Much appreciated.

handyguys 09-23-2010 08:40 AM

The issue with the wood retaining wall is it will eventually rot out. If its new, green, wet, pressure treated (PT) it may also warp or twist. The PT will eventually rot, some PT is better for ground contact than others. Check the rating.

The key to logevity will be to keep as much water away from the wood as possible. That means keeping it out of the dirt, put it on a stone base, back fill with stone and put in drainage where needed. your goal will be to minimize wood to dirt contact.

Unfortunately, say you have stone back fill with just an inch of dirt on top to grow grass. The grass wont do well because it will dry out. Its a trade off. If your going to use wood retaining walls you will want to find a middle ground (no pun intended). use gravel underneath and behind and use topsoil where you want to grow grass and home for the best.

Good luck

mudmixer 09-23-2010 08:42 AM

Stone dust will settle more in the end than if you use sand. Clean, rounded masonry sand can be forced into the joints better to interlock the pavers. There also som paver patterns that offer for interlock, which spreads the load or more evenly. The proper installation is the reason you can use the smaller interlocking true pavers to carry the load of a 747 or a huge 4 wheeled straddle loader for moving international shipping containers (40,000#).

You are just building a 10x12 patio for foot traffic, so the materials are not as critical as a 40 acre area.

Staggering the joints is always stronger, more stable and architecturally pleasing, but does take some planning.


rory_88 09-23-2010 10:36 AM

Thanks Handyguy. That was my plan - landscape fabric and then back fill with crushed stone. If it lasts 10 years I'll be more than pleased. Done right it should easily go that far.

Mudmixer, I have a yard of stone dust from taking up an old walkway. So I'm going to use that for the base layer. I could use masonry sand for the joints. Staggered joints are a must. I wouldn't think of doing it any other way. Note: these are not modern pavers but antique bricks. They will not interlock like a modern paver.

OK and finally, the water under the pad issue. I have decided to dig a french drain and tie it into the drywell. It is only a few feet of digging and it will ensure very good drainage.

Oh and how far do you think this bricks will settle when I run the plate compactor over them? 1/4 inch?

Thank you for all the good support. I'll take pictures and post up as I go.

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