Landscape timbers for playground edging

michiganguyAugust 14, 2014

Building a playground for my kids. Planning on bordering it with landscape timbers like this:

I realize these aren't the best and I will probably stain them to make them last longer. When I dig out the trench to put these in, should I drop in some gravel and compact it and then put these on top? (Planning two high for now)

I figure that would help with keeping them level and it better shape. If so, what type of stone should I use? I am assuming something similar to what you would use beneath pavers

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These so-called "timbers" really aren't going to last very long, but they may be good enough for what you're doing. Not convinced the stain will make a difference, but it won't hurt either. The gravel probably won't make much of a difference, but it might make a little diff and help you level. Since it's for drainage as well as leveling, you would be best off to use commonly available pea gravel... a clean, rounded stone ... not an angular chip with fines.

    Bookmark   August 14, 2014 at 4:20PM
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Thanks for the tips. I think your right about the landscape timbers. Looked at them today at home depot and wasn't really impressed. What would you recommend if I want to get something that will last longer? Any other recommendations? I am looking for someone to hold the mulch in, and for aesthetics.

For the gravel someone told me use some kind of limestone that compacts better. Dig the trench put it down, tamp it down real good then lay the timbers on top.

Thanks for help

    Bookmark   August 14, 2014 at 5:07PM
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If the primary purpose of the gravel is drainage and a setting bed, then rock that is roundish -- like pea gravel -- is better. No one is going to make actual contact with the gravel once the job is complete (like walking on it.) It will be buried and surrounded on all sides. Before it is surrounded, it will move around easier so be easier to level out when you tamp the timber on it. It's not going to make that much difference for a setting bed if you use paver base. BUT, pea gravel will drain faster and contain more air spaces than paver base when they are both compacted. If you have an area of compacted paver base and run a hose on it full blast, you will create a puddle. With pea gravel, the water will immediately drain through. It would not be possible to form a puddle.

That said, the better wood to use is regular treated lumber like 4" x 4" or 6" x 6". It is treated to withstand ground contact for some years. To let you know how bad those "landscape timbers" (the cheap ones) are, I once needed a really cheap temporary fence so used them as fence posts. One year later, I grabbed one of the posts and gave it a medium tug (just to test). It snapped off at ground level!! Really?? I checked a couple of others and they were similarly weak. I was very careful not to bump any of them after that since I needed to get one more year out of them.

I don't know the details of your project and am only trying to help you go in the direction you've already established for yourself. However, if I or others knew details and parameters of the project we might suggest an altogether different strategy. Just saying.

    Bookmark   August 14, 2014 at 8:51PM
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Thanks again for the follow up. I'm basically looking to do a playground in our backyard. I want to make it look nice so I want to do a border around the playground area, for looks and to hold the mulch in. I am planning on rubber mulch. I haven't done much landscaping but I want to do it right. More stuff below

Your advise is great, I think I will steer clear of the landscape timbers. Your advise is to go with something like this:


These are the regular pressured treated lumber you are talking about right? Pressure treated more thoroughly than landscape timbers (which I read the surface is only pressure treated)

I am building this over grass so my plan is to kill the grass with a spray, dig out the edge, lay down the gravel, then probably stack two high the 4x4's or 6x6's. Put some good quality landscape fabric down, install the playground, then dump the mulch in.

I wonder how deep the "ditch" I dig around the edge should be? I only want 3-4 inches of mulch... thanks again for all your help.

    Bookmark   August 14, 2014 at 11:06PM
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If the grade is relatively flat and level, it is not necessary to build the structure so that it sticks up above grade. Keeping it flush makes it safer and better looking. In the first example in the picture, the timber at the right edge of the structure is flush with grade so nothing to trip on and nothing sticking up adding clutter to the scene. Note that retaining the mulch is independent of the level of the grass. So the idea that a frame must be raised in order to retain mulch is false. The mulch level just need to be at the correct elevation ... not heaped above the frame. (This usually means excavating some soil prior to adding the mulch.) The second picture is an example of how the entire frame can be flush and still retain mulch. It's safer because there is nothing to trip on. If one falls, it's much safer to fall on a flat surface (even if it's hard) than it is to fall on a hard edge that's sticking up. Making the surface flush also opens up the options of materials that can be used. Straight sticks of lumber are usually limited to rectangular structures. Other flush edgings capable of separating mulch from turf can make easily make curves or straights. (I think they are easier to install, too, than heavy lumber pieces.)

Use the rubber mulch if you like, but research it first and try to find an example to appraise prior buying. Many people become less satisfied with it after using. One thing to think about is what happens at the end of this play area's life. Will it become trash, or will materials be re-incorporated somewhere else in another way. After a few years, lumber and rubber mulch will most likely only become trash.

    Bookmark   August 15, 2014 at 11:54AM
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first question, is this a playscape or swings or what? If you have some kind of playscape or swings you can fall from... 12" depth of engineered wood fiber mulch will give you a heavty cushion to fall into. I'd save whatever money you were going to spend on this edging/curb and omit it all together. Use a sod cutter cut out the sod, dig out the soil, and edge the bed like a regular bed except fill it up with the mulch.

if you have poor draining soil and believe you need to drain this hole you're making to fill with chips, then you have a new problem :-)

    Bookmark   August 15, 2014 at 1:15PM
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First thanks to both of you for the reply!

The grade is pretty flat, not going to be an issue. I think your right about trying to keep it flush with the yard. My thinking previously was build up a "wall" to contain the mulch. But this was because I was planning on not doing anything with the grass.

But what do you mean about "this usually means excavating some soil prior to adding the mulch"... do you mean basically what the other poster said, ripping up the sod?

If I do remove the sod, how deep does that usually go? Because I only really want to do about 3 inches of mulch. I thought removing the sod would be deeper.

Regarding the rubber mulch, when I bought the playground they threw in a bunch of rubber mulch... and it's only about a year old. So I have half of it already, will add more. I know getting rid of it at the end might be a hassle. Do you have any idea what the lifetime of this rubber mulch is?

This is a smaller playscape with 2 swings, slide, etc. The standard stuff. As I said before I already am doing the rubber mulch because I got a bunch of it from the sale.

Your idea about omitting the edging is interesting... but I think I want it for aesthetics.

I've never used a sod cutter... I imagine I can rent one. How deep do I have to go? That brings my problem mentioned above if I have to cut 6 inches down does that mean I am going to have to buy some dirt to fill in the 3 inches then 3 inches of mulch?

Thanks again for your help guys!!! Hope to get this figured out within the next day or two so I can get to work on it.

    Bookmark   August 16, 2014 at 11:51PM
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I meant to mention ... keep the border that divides lawn & mulch away from the play equipment so that it's not likely to be contacted by someone falling. Many people place it too close.

You've seen sod for sale. A sod cutter will cut it like that ... about an inch thick ... for saving the sod and reusing it ... and making the excavating a little easier. After cutting out the sod, then you dig out for and install the edging. Set it at the elevation you want it to be ... not according to imperfections of grade. Then excavate the cavity that will hold the mulch. If the grade is relatively flat, you could set the edging a little higher -- say 1 1/2" higher -- than the highest adjacent grade. When finished, you would want the mulch to be at 1" lower elevation to keep it contained. You want a 3" layer of mulch, so that means your excavation for mulch will be 4" below the top of the "edging". Raising the overall structure a little means you don't need to do as much excavating. You can use some of the excavated soil to raise the grade surrounding the outside of the play area, bringing it to the top of the edging ... making it flush with grade. (You'll have a little soil left over for filling low spots in the yard.) You could use any number of things for edging, but ultimately it needs to penetrate the grade at least a little more than the depth of mulch. BTW, the landscape fabric will not to anything to help keep out weeds. It's purpose at that level is to separate mulch from earch.... making it easier to disassemble this years later if you decide you want to do that. So the fabric that has little strength and tears easily is not the one to use. You could just as easily use a tarp punched full of tiny holes for drainage. I hope the illustration clarifies the basic structure assembly...

    Bookmark   August 17, 2014 at 9:20AM
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If it were my kids, I wouldn't use rubber mulch as I'd tend to err on the side of caution. The Consumer Reports brief linked below, concludes that it may be appropriate for gardens but not for playgrounds (though I wouldn't want it in my garden either) due to small pieces of steel and nylon from tire belting. They also cite potential leaching of chemicals from the rubber and I imagine it heats up far more than organic mulches like wood chips.

On a purely practical note, if organic mulches like woodchips escape from the play area (kids jumping, sliding and throwing things) they can be mowed over and will decompose into the lawn. Rubber mulch will need to be moved back into the play area before mowing.

Do a search for rubber mulch and then decide if you still want to use it.

Here is a link that might be useful: Consumer Reports rubber mulch

    Bookmark   August 17, 2014 at 9:42AM
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Thanks again for all your help. You've cleared up so much of my confusion in such a concise manner, I really appreciate it! Especially the illustrations... a picture is worth a thousand words!

You have me going in the right direction. I've mapped out my area to be 23ft x 22ft. I've calculated at 4 inches of mulch, it's about 150 cubic feet. I can get 77 cu ft of rubber mulch at home depot for $720. Like I said, I got some when I bought it... I would guess 30-40 cubic feet. So even if I bought one big back of mulch at $720 + what I have, I am still coming up short. So basically I have to decide if I want to spend $1000 + on rubber mulch OR go with regular mulch? I want to get 10 years out of this so that should factor in... my kids are young right now.

If I go with regular mulch, what kind should I get and how often would it probably have to be replaced? Trying to factor in the costs of replacing it every what, 3 years?

So I might get a landscaping company to come cut out the sod, would that probably be better (instead of renting one?) Also I have some spots on my lawn that could use the sod, it shouldn't be any problem moving it... right? Any rough idea how much it would cost 23ft x 22ft area to bring up the sod and maybe move half of it somewhere else? A couple hundred bucks?

So I get the sod dug up, that goes down an inch or two... then I still have to dig out a couple more inches of dirt, right? Should I be renting anything to do this, or just shovel it out?

Also if I want to do about 4 inches of mulch, does my edging have to be higher than 4 inches? I'm just going on what I see at home depot website... 4x4 and 6x6. In your diagram in looks like the edging is higher than 4 inches. Should I stack or just get a single piece of wood. Maybe 4x6?


Thanks for the reply. Read above... one of the main reasons I am going the rubber mulch is because I have some but now and thinking about organic mulch. And recommendations on something or should I have one of the local landscaping companies dump a bunch on my driveway?

    Bookmark   August 20, 2014 at 10:58PM
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"Trying to factor in the costs of replacing it every what, 3 years?" Just top dress to fill in the amount lost to decomposition. Every few years you might replace some, but not all. In 10 years, it's ready to be converted to a garden or landscape bed already full of nice compost. If you want to save $, get some tree trimming mulch (from work being done in your area, or pick it up). Fill the lower half (or a little more ... it will settle) of the cavity with that mulch (low grade) and fill the upper half with nice mulch. Reserve some nice mulch for top dressing as overall will settle a little in the first few days.

If it was me, I'd buy wood based mulch in bulk. Don't know what's available to you. Not pine straw or bark, something like cypress (wood chips) ... mulch that packs down and rots more slowly.

You would need to research sod cutting costs locally.

Just "shovel it [dirt] out" ... it's not that much. See if you can find good places to use on your own property. Or make a neighbor's day. And reserve some for touching up outside of your timber frame.

If mulch is 4" actual, then edging needs be more. The 6" x 6" timbers will look and work best. A single layer is enough. Do you have a plan to pin to earth?

    Bookmark   August 20, 2014 at 11:44PM
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Thanks for the quick reply :)

When calling landscape/mulch companies... what kind of mulch should I ask for? Cypress? I know there is lots available around here. In my beds I've used scotts nature scapes (when it goes on sale, $3 for 2 cu ft)... had good luck with that. But like you said probably need something bulk and I've never ordered mulch that way.

Mixing rubber and wood chip mulch would probably not be a good idea, right?

When you say touching up outside of the timber frame... I noticed in your diagram where you had that, but do you mean just spread the dirt on top of the grass?

I was going to ask you about pining the timbers in. Recommendations? Also, if I use wood chips, you wouldn't bother with a high quality landscaping fabric still?

Thanks again for all the info.

    Bookmark   August 20, 2014 at 11:57PM
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"Mixing rubber and wood chip mulch would probably not be a good idea, right?" Very right.

Yeah ... spread dirt on top of grass. Grass will grow through it and new grade will be established. If there are areas where dirt will be thick (greater than 2 1/2") use some of the sod you're taking out to establish new grade. But only where dirt is thick.

    Bookmark   August 21, 2014 at 12:04AM
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Getting close to getting started. Planning on renting a sod cutter to remove the sod. I have some dirt areas of my lawn that I am going to move it to. How should I prepare those? Just dig them out a couple inches deep?

Also for the timbers, I am looking at roughly 24 x 24 foot space. Should I just get 12 foot timbers and miter the corners?

How do I secure the timbers to the ground? I am guessing spikes but how long and do I pre-drill the hole for them?

Also a stupid question - should I put the mulch down and then put the playground on top of it, or put the playground on and then mulch around it?


    Bookmark   August 26, 2014 at 1:24AM
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Preparation for the areas to receive sod: smooth the grade to receive sod. Where the sod will meet existing grass there should be about 1" grade differential. Since the differential is little, depending on overall grading you may ignore it and "heal" the difference with loose soil on top of the existing grass, blending it. It's not necessary to remove 1" soil over the whole area ... only near the edge to be blended.

Don't miter corners. use square butt joints.

Hopefully, you're using 6" x 6" timbers. If that's the case you'll need only one layer of timbers to form the edging. Here's an method of how you may pin them to earth so that no connectors show. I'm not labeling the sketch; hopefully you can follow along.

First, set the timber framework in place as it will be in the end, so that everything is in plane and in line. Carefully roll each timber outward so that its bottom is at the top. At 6" from each end and at the center, pre-drill a hole to 3" depth and drive a landscape spike (8") into it so that 5" of the spike remains exposed. (The hole must be a smaller diameter than the spike so that the spike is driven very tightly.) There will be 3 spikes embedded per timber @ roughly every 6'.

Then, at the setting bed for the timber, dig a 6" dia. hole with clam shell post-hole digger, that will correspond to the location of the spike in the timber. The hole should be about 15" to 18" depth. A little more or less is inconsequential, but it needs to be below the frost line. If the hole flares slightly at the bottom it will keep the concrete from lifting upward later. Mix some concrete so that it flows but is not runny and fill each hole with it. Don't overfill. Roll the timber back into place so that each spike is aimed down into the fresh concrete. Adjust so that it is perfectly in place. Try to dig the hole depth so that is accepts about 25 lbs. (half of a small bag) of concrete. A little trial and error will help develop consistency.

At each corner, pin one row of timbers to the other with a spike or lag bolt in a pre-drilled hole. This will keep any separation from happening at the corners.

I'm not saying this is the only way to do this. It's A way that secures the timber from both horizontal and vertical movement, without holes and re-bar showing.

The mulch is installed after the play equipment is installed.

    Bookmark   August 26, 2014 at 11:31AM
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So many ways to skin a cat. I grew up in a cold climate where concrete is an underperformer, so I make my timber borders two timbers high. Dig the trench to depth as level as I can, and use sand or stone dust for fine leveling. Drill 1/2" holes all the way through the timbers in a couple spots and use a sledge to drive 18-24" pieces of 1/2" rebar into the soil. Then I set the next layer of timbers (staggered, obviously) and predrill all the way through both timbers with a 3/8" spade bit, then pin them together with a 1/2" galvanized spike. Predrilling 1/8" smaller keeps the wood from splitting but still allows the spikes to grab.

Either method works, but mine's quicker and is still totally durable

    Bookmark   August 28, 2014 at 5:26PM
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It's refreshing to come across a thread that's relevant to me right now at this very moment! :-) We're in the midst of putting our backyard together as we speak. The dirt has been tilled. I'm thinking we'll need to grade it prior to putting together the play structure.

Anywho, we were JUST at a retailer looking at rubber mulch today. The rubberiffic borders are outrageously expensive, IMO. We have plenty of railroad ties we inherited with the backyard but those things are so toxic, I'm wanting to completely extract those from my yard. I really liked your idea of the 6x6 pretreated timbers. I'm sure those have some level of toxicity to them but not nearly as much as the other! I think that's what we'll go ahead and try to use. For the money, I believe this is a feasible solution for us as well.

Thank you everyone for your contribution to this thread. It's been very helpful. Can't wait to see pictures!

    Bookmark   August 29, 2014 at 9:13PM
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