Author Topic: terrace wall - lumber choice (PT or cedar) or stone?  (Read 1057 times)

NaN

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terrace wall - lumber choice (PT or cedar) or stone?
« on: March 14, 2020, 07:40:51 AM »
In preparation for being quarantined (jk-probably just a weekend project), my project of choice is to build a few terraced walls and a few garden beds.

I am planning to make the garden beds out of 4x4 and 2x4 rough cedar. Not the cheapest option, but I think they will be sturdy and last 20 years in my climate. I was thinking of putting some gravel underneath the perimeter to help with drainage. These will mostly be used for annual vegetables. I am roughly going to follow this design: https://agrilifeextension.tamu.edu/solutions/raised-garden-beds/

For the terraced walls, I plan to extend a 16" and 8" rock walls about 40 feet. Right now my choice of timber vs rock is timber because it is way more affordable. My plan is to use the space behind the walls to plant raspberry bushes. The pressure treated timber these days "claims" to be safe for edible plants. However, I am on the fence (no pun intended) about using it. I could use cedar, but the wall will be 4x4 timbers not 6x6 with PT (based on what is available in my area) and it might not last nearly as long. A stone wall, while it would last forever, costs a lot, and would be lot more effort with placing. Maybe it is worth it? Anyone have any thoughts on PT timbers near fruit plants, and any thoughts on the rock wall vs timber wall?


lthenderson

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Re: terrace wall - lumber choice (PT or cedar) or stone?
« Reply #1 on: March 14, 2020, 04:14:03 PM »
I have made several raised beds with cedar 4/4 decking that can be found in most home centers and really like the stuff. As for the terraces, I know my preference would be to go with stones. I usually plan ahead though and buy them in the off season when they are deeply discounted. Don't buy them in the spring and summer when they are full price. The disadvantage is you might not have as much of a choice. I don't like using pressure treated near edibles even if it is supposed to be safe. The food safe PT wood also doesn't last as long as the worse for food PT that we had before it when soil is against it all the time. I've had to replace some 6 x 6 posts after ten years that rotted off. It may have been a bad batch.

NaN

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Re: terrace wall - lumber choice (PT or cedar) or stone?
« Reply #2 on: March 14, 2020, 08:53:08 PM »
After much thinking over the day, I am now leaning toward the stone wall. The new PT wood says it is safe, but that's exactly what they said about the last kind of PT wood. I just have to find the right stone (6-12" roundish, not blocky) that matches my budget.

The adjacent stone wall, probably installed 50 years ago, is just sitting on top of the soil with no drainage pipe (it is only 20" or so all, with 14-16" above the ground). It has aged really well, minus a few stones that have come loose. I will likely put a gravel bed underneath on this new one, and proper drainage, but something about the way the last wall was done, going against any modern best practices approach, and lasting amazes me.

Next I need to find the right approach for the mortar. I hear it is all in the mixture.

edit:
This.  https://www.laspilitas.com/garden/howto/rockwall.htm

Quote
Every day, before you go in after working on the wall, get yourself a wine cooler, beer, iced tea, coffee whatever, and a hose and water in what you've done. Don't make a muddy mess out of it, just set the stones and water the plants.

Quote
The lack of formality allows a rock wall to look good. If you make it too formal, you have to do a great job. If you do a good job and keep it simple, with a bunch of small mistakes, it will look good.

« Last Edit: March 14, 2020, 09:16:22 PM by NaN »

Fishindude

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Re: terrace wall - lumber choice (PT or cedar) or stone?
« Reply #3 on: March 15, 2020, 09:09:37 AM »
My raised bed gardens are 6x6 treated timbers, they work great.
I find the idea of buying rocks pretty funny.   Here in farm country there are piles on every farm in the fence rows, in the woods, etc. where farmers hauled them when cleaning up their fields.   Most will gladly let you have all the rocks you want.

NaN

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Re: terrace wall - lumber choice (PT or cedar) or stone?
« Reply #4 on: March 15, 2020, 06:00:44 PM »
I am going to be calling the local landscaping store tomorrow to see what the options are. I am not looking for 'fancy' stone that can run up to $500 per 1/2 ton. I am hoping there is something available at around $50 per 1/2 ton. I need at least four tons. If that indeed is possible that puts in the cost of timbers. While the timbers might last 40 years (stones are forever :) ), the thought of putting treated lumber next to edible plants does not sit well with me.

Today I finished digging a 10"x2'x40' trench. A nice surprise was finding a french drain that took water away from the back of the house that faced the slope. I am glad that exists!

For the future, it is looking like 2 yards of gravel, 3 yards of rip rap or similar stone, and maybe 10 yards of soil/compost mix. Should be a fun time!

lthenderson

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Re: terrace wall - lumber choice (PT or cedar) or stone?
« Reply #5 on: March 16, 2020, 02:49:06 PM »
My raised bed gardens are 6x6 treated timbers, they work great.
I find the idea of buying rocks pretty funny.   Here in farm country there are piles on every farm in the fence rows, in the woods, etc. where farmers hauled them when cleaning up their fields.   Most will gladly let you have all the rocks you want.

I'm quite envious of your environment. Here where I live, most rock is 20 feet deep under 19 feet of clay. I've always dreamed of what I could do with a bag of mortar, a trowel and rocks everywhere I look.

To NaN, I am of little help on mortar. The only rocks I've installed are the flat, dry stack landscape kind and like many kinds of such projects, if you do the prep work well before setting them in place, they stay in place and last lifetimes. 

Fishindude

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Re: terrace wall - lumber choice (PT or cedar) or stone?
« Reply #6 on: March 16, 2020, 06:22:16 PM »
I'm quite envious of your environment. Here where I live, most rock is 20 feet deep under 19 feet of clay. I've always dreamed of what I could do with a bag of mortar, a trowel and rocks everywhere I look.

To NaN, I am of little help on mortar. The only rocks I've installed are the flat, dry stack landscape kind and like many kinds of such projects, if you do the prep work well before setting them in place, they stay in place and last lifetimes.

I'm in north central Indiana and yea, we have an abundance of big, beautiful, colorful field stone.  One of our farms has an area where there must be 20 dump trucks of the stuff piled up.   Poor farmers back in the day, hauled all of those rocks off their fields pre-tractor with their backs, horses and a skid or wagon.    Now we have mechanical rock pickers and heavy equipment.

I've personally used it to lay up the wall behind my woodstove and to face the entire front on my big bar in man cave.   Our entire porch (125 year old house) is field stone with big stone pillars, no doubt picked up locally.   Keep thinking I want to do a couple great big stone pillars at the driveway entrance off the road, but haven't gotten around to it yet.  I've just used pre-mixed bagged mortar like you would lay brick with to do my stone work.   It's a slow process, your mortar needs to be pretty dry and you can only stack so high or the rocks will want to roll away.

My cabin is roughly 200 miles south of here in southern Illinois and apparently the glaciers stopped before they got there, because you can't find a rock, other than some flat stuff in the creek bottoms.

big_owl

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Re: terrace wall - lumber choice (PT or cedar) or stone?
« Reply #7 on: March 17, 2020, 09:38:43 AM »
Back when I made half a dozen raised beds about ten years ago I ended up using railroad ties.  I couldn't afford that many treated pieces of lumber and you can get old RR ties delivered for cheap.  I did a lot of research on the safety of it and it was rather dubious, but I did line them with waterproof landscaping fabric before backfilling with soil just to be safe.  They've held up very well and I think they look nicer than treated lumber - more earthy, though probably not as nice as stained cedar.  Another benefit I hadn't thought of is because RR ties are so heavy and wide you can easily walk around on top of them and they're stable.  I can easily jump from one side of the raised bed to the other and also they work as a comfy seat as well.

Being in a different financial situation now, I think I'd use thick cedar.  The only reason being that RR ties are very heavy and my 39yo back isn't my 29yo back anymore.  RR ties also dull your chainsaw relatively fast. 

Stone terraces would be best but I'd pay to get it done because of 39yo back again. 

Mighty Eyebrows

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Re: terrace wall - lumber choice (PT or cedar) or stone?
« Reply #8 on: March 17, 2020, 08:36:44 PM »
After much thinking over the day, I am now leaning toward the stone wall. The new PT wood says it is safe, but that's exactly what they said about the last kind of PT wood.
Stone is always good, but you should link to the PT type you are contemplating. That would allow us to help guess its potential toxicity. Many kinds now are mostly copper, with no arsenic.

(As for those people without much rock, I am envious of soft soil. We have bedrock 12" below the surface here, which makes digging utility lines a real project.)

NaN

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Re: terrace wall - lumber choice (PT or cedar) or stone?
« Reply #9 on: March 18, 2020, 09:06:43 AM »
The wood is SYP with CA-C pressure treatment. I realize the toxicity is considered "safe" but the science does say the chemicals leach into the soil. Whether that is acceptable is based off a number someone came up with, and the science why that number was chosen is not so clear. For me, better just to stick with stone.

Fishindude

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Re: terrace wall - lumber choice (PT or cedar) or stone?
« Reply #10 on: March 18, 2020, 12:02:38 PM »
I figured someone would eventually jump on this thread and plant the fear of being poisoned by using treated lumber.
I'll take my chances with my treated lumber raised beds, thanks.

NaN

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Re: terrace wall - lumber choice (PT or cedar) or stone?
« Reply #11 on: March 18, 2020, 09:14:29 PM »
No problem @Fishindude . I think everyone should just make their own informed choice and do what they feel okay with. You are welcome to try to convince me otherwise other than just saying "they are great".

Mighty Eyebrows

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Re: terrace wall - lumber choice (PT or cedar) or stone?
« Reply #12 on: March 20, 2020, 09:10:12 PM »
The wood is SYP with CA-C pressure treatment. I realize the toxicity is considered "safe" but the science does say the chemicals leach into the soil. Whether that is acceptable is based off a number someone came up with, and the science why that number was chosen is not so clear. For me, better just to stick with stone.
We tend to have more ACQ here but the Copper Azole is around as well. The CCA that they replaced had arsenic that was best avoided, but really only affected a small area of soil near to the treated wood. Still, I wouldn't personally use CCA near food plants.

The azole compounds in CA are used in agriculture, although that may not change your feelings about them:
https://en.wikipedia.org/wiki/Triazole

The "quat" in ACQ is also used elsewhere but, again, may not be your personal choice:
https://en.wikipedia.org/wiki/Didecyldimethylammonium_chloride

They are much better than CCA, although you need to choose the right screws/nails so the copper doesn't corrode them. For myself, I have used them in projects (deck, etc.) and think they are fine for ornamental garden beds. For anything food related, stone walls are probably better if you have concerns. YMMV.

If I needed to use ACQ for a garden bed, I might make a small gravel drainage layer along the wood and cover with landscape fabric. I don't think the water leaching would be particularly strong past 1/2" of gravel. If much of it leached from the wood, it wouldn't make a very good preservative!

MrSal

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Re: terrace wall - lumber choice (PT or cedar) or stone?
« Reply #13 on: March 23, 2020, 10:31:52 AM »
In preparation for being quarantined (jk-probably just a weekend project), my project of choice is to build a few terraced walls and a few garden beds.

I am planning to make the garden beds out of 4x4 and 2x4 rough cedar. Not the cheapest option, but I think they will be sturdy and last 20 years in my climate. I was thinking of putting some gravel underneath the perimeter to help with drainage. These will mostly be used for annual vegetables. I am roughly going to follow this design: https://agrilifeextension.tamu.edu/solutions/raised-garden-beds/

For the terraced walls, I plan to extend a 16" and 8" rock walls about 40 feet. Right now my choice of timber vs rock is timber because it is way more affordable. My plan is to use the space behind the walls to plant raspberry bushes. The pressure treated timber these days "claims" to be safe for edible plants. However, I am on the fence (no pun intended) about using it. I could use cedar, but the wall will be 4x4 timbers not 6x6 with PT (based on what is available in my area) and it might not last nearly as long. A stone wall, while it would last forever, costs a lot, and would be lot more effort with placing. Maybe it is worth it? Anyone have any thoughts on PT timbers near fruit plants, and any thoughts on the rock wall vs timber wall?

Dont use 2x4 s!! I used 2x4 PT because 1x4 PT wood and 2x4 are the same price. And I though, well, double the material for rot to happen. These will last longer.

Well, I built the planters and they were a hassle to move even without dirt. I believe my 2x4s planters weigh about 400-500 lbs each! With dirt, Probably 600-700 lbs.

Using 2x4 as posts/supports and then 1x4s as the walls should be plenty! I think.

Fishindude

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Re: terrace wall - lumber choice (PT or cedar) or stone?
« Reply #14 on: March 23, 2020, 01:22:12 PM »
Dont use 2x4 s!! I used 2x4 PT because 1x4 PT wood and 2x4 are the same price. And I though, well, double the material for rot to happen. These will last longer.

Well, I built the planters and they were a hassle to move even without dirt. I believe my 2x4s planters weigh about 400-500 lbs each! With dirt, Probably 600-700 lbs.

Using 2x4 as posts/supports and then 1x4s as the walls should be plenty! I think.

Sounds like your beds are elevated on legs with a bottom?
My beds have no bottom.   Just built perimeter walls out of treated timbers and set them on the ground where we wanted them, they are 30" tall.    Filled about half depth with gravel, then top half with good garden soil.

NaN

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Re: terrace wall - lumber choice (PT or cedar) or stone?
« Reply #15 on: March 23, 2020, 03:39:08 PM »
Dont use 2x4 s!! I used 2x4 PT because 1x4 PT wood and 2x4 are the same price. And I though, well, double the material for rot to happen. These will last longer.

Well, I built the planters and they were a hassle to move even without dirt. I believe my 2x4s planters weigh about 400-500 lbs each! With dirt, Probably 600-700 lbs.

Using 2x4 as posts/supports and then 1x4s as the walls should be plenty! I think.

Did you see the Texas A&M link? Those were not 700 lbs. I think cedar 2x4s are about ~10 lbs each. For twelve 2x4s and a couple 4x4, that is only 150 lbs at most. Another interesting point about PT wood, it has considerable extra weight from the PT chemicals.

I ordered the rock for my wall and it cost me $250 for the length of wall I want. It cost me $130 for the gravel base. Labor for digging the trench was just a few weekend days.

(Well, I might get the rock in this week for working on it this weekend. Looks like my state just shut down all non-essential businesses. I mean, I get it - a landscaping company is non-essential. But how does a guy in a dump truck who I don't have to even come close to be a risk to public health? )

Car Jack

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Re: terrace wall - lumber choice (PT or cedar) or stone?
« Reply #16 on: March 25, 2020, 10:49:24 AM »
Good choice on stone.  When we bought our house, there was a 10 year old retaining wall built from railroad ties.  Fast forward 10 years and there is visible rotting on the face of many pieces.  They become a deluxe resort for carpenter ants who take nightly excursions over to our porch.  When we had sidewalks put in with pavers and another stone retaining wall rebuilt, we opted to remove all the timber and replace it with stone.  Best decision we ever made.  We also replaced all the bed mulch with landscape fabric and stone.  Another great decision.  When fall comes, I take my Echo backpack leave blower and just blow off the leaves, leaving the stone in place.

MrSal

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Re: terrace wall - lumber choice (PT or cedar) or stone?
« Reply #17 on: March 25, 2020, 03:42:28 PM »
Dont use 2x4 s!! I used 2x4 PT because 1x4 PT wood and 2x4 are the same price. And I though, well, double the material for rot to happen. These will last longer.

Well, I built the planters and they were a hassle to move even without dirt. I believe my 2x4s planters weigh about 400-500 lbs each! With dirt, Probably 600-700 lbs.

Using 2x4 as posts/supports and then 1x4s as the walls should be plenty! I think.

Sounds like your beds are elevated on legs with a bottom?
My beds have no bottom.   Just built perimeter walls out of treated timbers and set them on the ground where we wanted them, they are 30" tall.    Filled about half depth with gravel, then top half with good garden soil.

Yes i understood wrong what your goal was. I built mine just for actual planters (boxwoods, and other type of perennials, bushy type of plants)

BDWW

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Re: terrace wall - lumber choice (PT or cedar) or stone?
« Reply #18 on: March 26, 2020, 02:26:41 PM »
I've been thinking about building these for boxes.

https://www.youtube.com/watch?v=x7jz96MDvyo

hint: Turn playback speed up this guy talks like molasses :)
« Last Edit: March 26, 2020, 02:36:20 PM by BDWW »

NaN

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Re: terrace wall - lumber choice (PT or cedar) or stone?
« Reply #19 on: March 26, 2020, 05:03:20 PM »
I've been thinking about building these for boxes.

https://www.youtube.com/watch?v=x7jz96MDvyo

hint: Turn playback speed up this guy talks like molasses :)

That is a pretty good idea! I would say you want to add some reinforcement in there, like lath wire or something else. But, hey, my rock wall is essentially the same thing, with a similar mixture just larger "particles" for reinforcement.

NaN

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Re: terrace wall - lumber choice (PT or cedar) or stone?
« Reply #20 on: March 26, 2020, 05:17:00 PM »
My rocks came in yesterday. A mixture of compost/top soil is arriving tomorrow for adding in once the wall is up. Here are a few pictures of the progress.


Hotstreak

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Re: terrace wall - lumber choice (PT or cedar) or stone?
« Reply #21 on: March 29, 2020, 09:21:59 PM »
You mentioned filling the bottom half of your beds with gravel, and using soil for the top half.  Usually this is not a good idea.  The gravel doesn't improve drainage in your growing medium, it just reduces your soil volume.  Is there some specific reason you want to do this?

NaN

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Re: terrace wall - lumber choice (PT or cedar) or stone?
« Reply #22 on: March 31, 2020, 07:33:13 AM »
Yeah, exactly @Hotstreak. The gravel is not for drainage, but the more I researched it looks it is meant to be a good base for the wall. It was tampered quite a bit, and then I used a little bit of coarse sand and gravel mixture to put under the first layer of rock. Drainage is being accommodated by several weep holes along the wall (one every 2-3') at about 1/3 the height. Plus the rock wall itself is not going to be "water tight".

In reality I probably could have even done this without the gravel. Our soil is so hard and compacted it could have been fine. The wall that is a the bottom of the picture just sits on the soil. It has no drainage (just whatever can seep through the rocks) and it has lasted 60 years. Though this will have better soil for the raspberries, so I guess having the gravel base wasn't a terrible idea, and the installed weep holes might be worth it. I specifically decided against a 4" perforated tub since it took up so much space and this is really a garden bed and not a true structural retaining wall.

Here is progress from last weekend. I learned a lot about how to best mix up the mortar for this project. I'll comment on that sometime later.


Mighty Eyebrows

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Re: terrace wall - lumber choice (PT or cedar) or stone?
« Reply #23 on: March 31, 2020, 01:12:56 PM »
Nice work!

A gravel base for a wall is always a good investment.

NaN

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Re: terrace wall - lumber choice (PT or cedar) or stone?
« Reply #24 on: April 05, 2020, 08:44:19 PM »
After another day and half this weekend the wall is pretty much done, with 65 raspberry bare-roots planted and ready to start growing! I still have some left over old dirt piles to move to other parts of the yard, about 3 yards of good top soil/compost mix, and two fairly large piles of rocks. Overall, I am quite happy with the result! I may even build another one above the upper row towards the sloped section next to the fence. Likely end of year or next year project.

A few things I learned along the way:
  • Be conscious of where you are throwing your dirt at the beginning - it helps to move it down hill at the end instead of up, or "wheelbarrow" it up hill before the wall is made :)
  • Mortar is best, when manually mixed, by a pan and a garden hoe. I found this way better than a high torque paddle mixer in a 5-gallon bucket. I used 20 bags of 80 lb mortar for 80 linear feet of wall. So 1 bag maybe 4 ft of wall
  • This probably took twice as long as a lumber wall, but "hopefully" it lasts longer than I am around
  • It helps to sort the rocks in size, and then move them close to where you will need them before mixing any mortar.

AccidentialMustache

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Re: terrace wall - lumber choice (PT or cedar) or stone?
« Reply #25 on: April 05, 2020, 10:17:00 PM »
I hope you are not expecting the walls to contain the raspberries... At least if they are anything like my dad's, nothing short of napalm contains them and even that probably only for a year.

NaN

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Re: terrace wall - lumber choice (PT or cedar) or stone?
« Reply #26 on: April 06, 2020, 06:58:44 AM »
Raspberries have been contained in other planters for years. I am not too worried about it. You should cut them back considerably every year, so they do require maintenance.

lthenderson

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Re: terrace wall - lumber choice (PT or cedar) or stone?
« Reply #27 on: April 06, 2020, 11:59:53 AM »
Excellent work! If I had a source of rock, I would like to do a project similar to that on our land which is mostly steep slopes. I like the though of terraces and plantings. Let me know if you hire out!