# Will deck rot if in contact with soil?



## robido (Jun 25, 2020)

Hi!

I have a treated wood deck, and I am planning to add new topsoil to increase the height of the lawn by almost 4 inches. The steps have 7 inches rise each, but the last step has 11 inches relative to the soil.

How can I prevent the deck from rotting when in constant contact with the ground?



I was also experimenting with adding an extra piece of wood before I raise the soil against it. It would help when doing the weed eater, as the concrete bricks make it harder (and does not look as nice).



Any ideas? Should I put an inch or two of rocks along the wooden edge, instead of soil?


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## TheEggMan (Jun 8, 2020)

Any wood in constant contact with the soil will eventually rot. Treating the lumber will obviously prolong the time till that rot destroys the wood. How long will it take? I doubt anyone can give you an accurate estimate. There's so much variation in the quality of treated lumber and the conditions at your location.

The safe bet is to figure out some way to keep the soil away from your deck/stairs. You'd have to figure out some way to cut about 4" off the bottom and increase the height of those concrete blocks you have the wood sitting on.


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## robido (Jun 25, 2020)

Thanks for the tips. I'll think about what I can do then. Maybe I could make a narrow trench in the soil, and fill the trench with rocks. That should prevent the last step from staying in contact with moist soil.

For the side, I was thinking of adding rock like that, but not sure yet:



I could go all rocks around, but the last step will be uncomfortable bare feet, and I feel its too much rock:


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## stacik84 (Feb 27, 2018)

Definitely like your last option the best, with the rocks around the perimeter. Some River Rocks (most expensive route) will look great!

You can also utilize stone, instead of rocks. Bluestone (pricey) or even molded concrete (shaped in a way to look "natural"). You don't need a ton of material, but It would make your area look much cleaner and sharper.

My 2 cents!


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## Allan-00 (Aug 6, 2019)

I agree with the last option as well. It looks good and will increase the longevity of the wood.


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## quattljl (Aug 8, 2018)

You can't prevent the wood from rotting, but you can (and should) use ground contact treated lumber for your deck. The tag on the boards should tell you what it is rated for (above ground, ground contact-general use, or ground contact-heavy duty). Each manufacturer may use its own verbiage but generally it will say something like this.


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## robido (Jun 25, 2020)

Thanks for all your tips it puts me in the right path! I will think about this over the winter, and come up with a plan I will do in summer 2021. With the lawn work, newborn, and work, I won't have time to do much more this season.


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## hsvtoolfool (Jul 23, 2018)

As an aside, Black Locust is a common North American wood species that is incredibly rot and insect resistant. In fact, it's superior to modern pressure treated lumber. Black Locust fence posts can last 100 years directly in dirt. The common name for black locust is "post oak" for this reason. America pioneers used black locust timbers as the foundation for log cabins and barns that still exist today.

Black Locust is considered a "trash" tree by most folks. It grows and spreads so fast that it's considered "invasive", has large thorns, and is a general nuisance to farmers and cattlemen. Land owners will often let you harvest these trees for free since they're a pain. But an 80 foot tall black locust can provide some very nice dense timbers along with a bunch of superior firewood. It's good for decking.


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## robido (Jun 25, 2020)

Wow thanks for sharing that knowledge! I wonder if I can find that wood for sale in my area.


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## hsvtoolfool (Jul 23, 2018)

@robido. Sorry I didn't notice that you were in Canada. Black Locust has spread far North as New York State and eastern Canada, so maybe. Black Locust is considered an "invasive" species in many States / Nations and they try to keep it out. But others deliberately imported the tree because it's pretty darn useful.


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## ken-n-nancy (Jul 25, 2017)

I notice that you have pavers adjacent to the deck in an area. I would suggest putting pavers down, maybe only one row of them, all the way around the deck, and possibly having a small "level-with-ground" area of them at the bottom of the stairs. The pavers will not hold water like soil, so even if touching the wood, they will not encourage rot anywhere near as much as direct soil contact. You do want to keep them about a half-inch away from the wood, so that the gap between them and the wood doesn't fill with sediment. That area can be blown out seasonally to keep sediment from filling up the half-inch gap.

Below is a picture of what I'd suggest. (Photo taken from the wrong angle, but you'll get the idea; the area in question is in the foreground.) We did this in the exact same situation when raising our soil about 2 to three inches in our back yard six years ago, and it has held up well. We used pavers for the "ground step" and used granite cobblestones along the sides (which isn't seen in the photo below).

Photo from our back yard renovation in 2014:


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## robido (Jun 25, 2020)

@ken-n-nancy I really like your idea of a pavers ring around the perimeter, and the landing at the end of the stairs. Do you have any stone dust or something to hold them in place, or just bare soil? Also, when laying soil, what target height should I aim for, relative to the paver's surface? I suppose if I can end up with a flush level, I can extend over the pavers with the mower, and it also reduces the risk of someone grabbing foot on the edge. I saw your journal you seem to have layed a lot of pavers!


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## ken-n-nancy (Jul 25, 2017)

robido said:


> Do you have any stone dust or something to hold them in place, or just bare soil? Also, when laying soil, what target height should I aim for, relative to the paver's surface? I suppose if I can end up with a flush level, I can extend over the pavers with the mower, and it also reduces the risk of someone grabbing foot on the edge. I saw your journal you seem to have layed a lot of pavers!


For the landscaping granite cobblestones around the flower beds for the lawn, I just have them set into the soil. They are pretty heavy and stay put well, especially after they've gone through a winter which really fixes them into the surrounding soil. They really don't move around over the winter unless they are stepped on during "mud season" -- being that you're in Gatineau, I know you are familiar with that!

I have strived to have the granite edging cobblestones be at or slightly above the height of the soil (less than a half inch difference). This is for two reasons: (1) by being at (approximately) soil height, I can roll the lawn mower wheels on them and still get the same cut quality as everywhere else, and (2) by being just slightly above soil height, water doesn't puddle on them, but flows down into the soil instead.

For the jumbo-sized cobblestones at the driveway and roadside edges, since these regularly take vehicle weight, I have taken a bit more care to support them well underneath. I have used each of stone dust, masonry sand, play sand, and regular old soil, with good results. The key with any of these is to make sure that the base underneath is well compacted. I use a small sledgehammer as a tamper to pack these down well under the ones intended to hold vehicle weight. I haven't had any problems with them moving around. A few in the lowest spots where water drains from the driveway have become a little lower (say a quarter inch) over a period of seven years, but not enough of a difference to get me to reset them yet.


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## robido (Jun 25, 2020)

@ken-n-nancy thanks for all the tips, this is great info. I did exactly like you suggested today for my front lawn regrading, leaving about 1/4 under the height of the paver step.

I will think about my plan for the deck for next spring. Maybe I'll expand the cobblestones idea for around the shed, as I don't like the grass growing and touching the shed siding.


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## ken-n-nancy (Jul 25, 2017)

robido said:


> @ken-n-nancy thanks for all the tips, this is great info. I did exactly like you suggested today for my front lawn regrading, leaving about 1/4 under the height of the paver step.


Glad to have been of some help in offering some ideas for you to think through want you wanted to do.



robido said:


> I will think about my plan for the deck for next spring. Maybe I'll expand the cobblestones idea for around the shed, as I don't like the grass growing and touching the shed siding.


What I've done in some similar places is to have a "sailor course" of granite landscaping cobblestones along the side of any linear feature that I want to be able to keep the grass a little away from the linear feature. Depending upon how much width you need, you could instead do a "soldier course" or a double sailor course (if the feature is straight). Pavers would work just as well as cobblestones. (Actually, the pavers would be easier to lay due to uniform height and shape -- the rough cobblestones are all different, making laying them a little more of an adventure.)

Another reason I like the cobblestone edge in this case is that the mower wheels ride on the rock instead of compacting the soil right at the edge of the structure, which tends to wear a track in the grass at that spot, particularly right up against a wall, where it tends to get less sun when on the shady side of the structure. The issue of running in the same place every time is slightly lessened for the opposite side of the mower (away from the wall) since, being nearly two feet away from the wall, it gets a bit more sun and can tolerate the wear a little better. Ideally, the rock border would be wide enough that mowing tracks can be varied with each mowing. I have that in some other places on our property where I have a foot or two of crushed rock up against the wall, with the granite cobblestones as edging. Photos of a couple of these can be seen in an old posting of our 2014 backyard renovation.


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## robido (Jun 25, 2020)

@ken-n-nancy I never heard those terms before - sailor/solder course, so I googled a bit and learned a few things. I think this would make a nice project. Let's say instead of a pavers edging, I used an aluminum edging for time/cost/space saving. Would the mower be ok to ride directly on stones?


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