Wood garage partially underground + termites - advice requested

[Sibley]

My title sucks, sorry. Need some ingenuity.

My garage is early '50s. Cracked slab, wood framing and siding, 1.5 car. As troublesome as it is, its functional and in line with the rest of the neighborhood, so keeping it. Sometime after the garage was built, the dirt level in the backyard was raised, so that the bottom 8-10 inches of the garage siding is actually underground. A couple years ago, I did a huge "fix the garage" project, during which I dug out all around the garage, replaced a ton of rotten wood (including the sill plate on 2 sides), and then had to figure out how to fill the trenches around the garage while also trying to keep the dirt from contacting the wood.

What I did was I put gardening cloth in the trenches, then put in clean rocks. Over the past 2 years since I did it, the rocks have settled and sunk a bit, and dirt/plant matter has gotten into the rocks. So now there's a decent amount of dirt in with the rocks. It grows weeds.

Well, there are now termites in the mix. Seem to have caught it early, and the pest control guy only found evidence of them in one corner. Since I'm doing the treatment and we'll have to dig out at least some of the rock, I'm wondering if it makes sense for me to dig it all out and redo these trenches so they last better.

I have several issues:
--how to prevent the weight of the rocks from just sinking further and further down
--how to prevent the dirt side from pushing in and just filling up the rocks
--how to manage water so maybe I don't just rot out the garage right away
--the soil is soft and sandy, it doesn't stay where you put it

My thought was maybe I can put some kind of hard foam on the bottom to fill up most of the space, then put rocks on top of that. If I combine that with some sort of flat landscaping rock holding back the dirt/rest of the yard, that might work. But I really don't want to do this then find out that it's not working for some easily foreseeable reason.

Thoughts?

[Sibley]

Pictures. The overall garage, plus 2 sides of rocks. The rocks are 6-10 inches deep, and go to the bottom of the slab.

[Sibley]

Modified plan:

Concrete pavers set vertically to hold back the dirt. Then water permeable ground cloth or whatever it is. Then, get 4 inch PVC pipe, cap the ends to keep junk out, and lay them down in the trench as space filler. Then put rocks in to the desired level.

What do you think?

[lthenderson]

I would not have any material, rock, dirt or otherwise in contact with siding. I would regrade it so that everything is below the top of the slab level. This might mean retaining walls, french drains and such in order to get the water to drain away and not puddle up next to the foundation. Since garages don't have basements, all you are doing is keep the water level below the top of the slab and from touching the siding.

I haven't dealt with termites but I have read that the best solution for termite prevention is to put as much non-edible material between the ground and your house. They don't like daylight and so have to build tunnels on concrete to get to the wood since they can't make tunnels within concrete. The bigger the distance, the easier it is to spot tunnels and treat before they do damage. You basically have zero distance so you are relying on treatment only. I would think the solution will be just to sign up for a regular treatment to keep them at bay, even if you solve the elevation/siding issue.

[AccidentialMustache]

May sound crazy, but... could you jack up that wall and sawzall off the underground portion and replace with cinderblock? Wood below grade is going to be a continual source of disaster. You'll probably still need to water-seal the cinderblock otherwise it'll just wick it to the wood but if you have to dig out the rock anyway, you'll have access to do so.

[Fishindude]

I would not have any material, rock, dirt or otherwise in contact with siding. I would regrade it so that everything is below the top of the slab level. This might mean retaining walls, french drains and such in order to get the water to drain away and not puddle up next to the foundation. Since garages don't have basements, all you are doing is keep the water level below the top of the slab and from touching the siding.

This !
Also - Once you have the pro rid you of termites, get some Home Defense and get in the habit of spraying around the perimeter of your building(s) several times every year, it's cheap insurance.

[Sibley]

So re regrading..... I'd have to regrade the entire 125 x 50 ft property, including messing with sidewalks, stairs, plumbing, fence, all the landscaping, oh and my batshit crazy neighbor (dx'ed, and she's decided she personally hates me). Nope. I have a hard enough time mowing the lawn sometimes with her craziness. I would prefer the garage rot to the ground over that.

If anything, I should knock down the entire garage and rebuild it. The slab isn't worth keeping, its in 6 pieces and each piece angles differently. But I'm not prepared to put that kind of money into it.

I am intrigued with this retaining wall and drain idea. Are you suggesting that I dig out the rock, do various work to hold back the dirt and manage water, and leave the trench, permanently? (at least until I decide to rebuild the garage)

[lthenderson]

So re regrading..... I'd have to regrade the entire 125 x 50 ft property, including messing with sidewalks, stairs, plumbing, fence, all the landscaping, oh and my batshit crazy neighbor (dx'ed, and she's decided she personally hates me).

Absolutely not. I don't think you understood what I'm trying to say. All you have to do is regrade say a few feet away from the perimeter of your garage digging down until you are below the slab grade. You can retain the dirt from the rest of your yard with retaining blocks. To handle the water between the retaining block wall and your garage, you install a french drain set in gravel and landscape fabric. All you are doing is keeping the dirt away along with easy access for termites and other bugs and taking care of the water so that area doesn't turn into a shallow pond.

[Frankies Girl]

I am in the home stretch of fixing a rotting wood deck/termite situation myself, and totally agree from everything I've read and seen personally - the best solution is get the structure out of contact with the ground and try to reduce any water/ponding. If this is a garage where you drive a car into it, then you'll likely be looking at a major work, but if it's more like a shed structure - then you may be able to get the structure raised using jacks and concrete support piers. There are ways to pick up and move structures, repour a foundation and then set the structure back on it (house/mobile homes do this).

But you may not want to deal with this stuff for a small building (my dealing with a 10 foot x 10 foot deck was pretty much my limit), so if you're okay with the structure eventually being torn down/rebuild with an above grade foundation, my suggestion is to do termite treatments and try to get french drains/retaining walls as @lthenderson suggests to funnel any standing water out as well as you can, and keep an eye on it until you decide if it's worth getting it rebuilt with a decent foundation eventually.

No wood, no matter what it's rated/treated with/whatever is going to last without rotting if it's touching dirt. My deck was built out of pressure treated pine, and everyone around my area is shocked it lasted longer than 10 years. (NOTE: It was like this when I bought the house)

Adding the rocks is only going to make things harder in my opinion, because of what you are already seeing - they make it easier for decaying organic matter to collect and allows for weeds to grow, you can't actually mow/clean it easily, and the rocks are going to sink/migrate because nature is a constant and ground settling/buildup of debris/movement of the pebble/stones. You could try adding a containing border, but it's not going to really help in the long run as you didn't raise the structure, you just exchanged some of the existing ground level with the stones and the garage is still in contact with ground & water, and in another few years, there's going to be a good amount of dirt in the stone/rock border and you're back to where you started again, but having to dig out a bunch of stones to boot and deal with the occasional pebble projectile when you mow anywhere back there.

Termites (at least the subterranean ones I'm dealing with) can only survive in damp/darkness and they are drawn to rotting wood. They will die if they dry out (why they build mud tunnels) and if they are exposed to light as well. So the main things are: remove the damp, remove the darkness, and making sure they don't have direct access to wood (no attractive materials in contact with the ground).

And one of the things I also learned: termites are EVERYWHERE. Even if you got the immediate area treated, they'll still be in your yard, the neighbor's or down the street even. You'll want to treat your whole property to ensure that if they do come back to check out your house, it's not easy, and they'll start dying if they stroll through. I am DIY perimeter trenching my house/all of the deck footprint with Taurus (generic Termidor). I've done extensive reading on how to do it right, so I'm hopeful I don't have to deal with this mess for a least another 5-10 years.

[Sibley]

So re regrading..... I'd have to regrade the entire 125 x 50 ft property, including messing with sidewalks, stairs, plumbing, fence, all the landscaping, oh and my batshit crazy neighbor (dx'ed, and she's decided she personally hates me).

Absolutely not. I don't think you understood what I'm trying to say. All you have to do is regrade say a few feet away from the perimeter of your garage digging down until you are below the slab grade. You can retain the dirt from the rest of your yard with retaining blocks. To handle the water between the retaining block wall and your garage, you install a french drain set in gravel and landscape fabric. All you are doing is keeping the dirt away along with easy access for termites and other bugs and taking care of the water so that area doesn't turn into a shallow pond.

Got it, yeah I was misunderstanding. What would you recommend re drop off danger? It is a possibility, unless I do a gradual slope which would be way more work upfront. The depth of dropoff would vary because the slab is not level anymore.

Also, what would you recommend I do in the lowered area? I can't leave it as bare dirt, it will grow weeds. Even with gravel and landscaping fabric, it will collect organic matter over time. Should I do some sort of ground cover plant? That would help with absorbing water as well.

[Sibley]

I am in the home stretch of fixing a rotting wood deck/termite situation myself, and totally agree from everything I've read and seen personally - the best solution is get the structure out of contact with the ground and try to reduce any water/ponding. If this is a garage where you drive a car into it, then you'll likely be looking at a major work, but if it's more like a shed structure - then you may be able to get the structure raised using jacks and concrete support piers. There are ways to pick up and move structures, repour a foundation and then set the structure back on it (house/mobile homes do this).

But you may not want to deal with this stuff for a small building (my dealing with a 10 foot x 10 foot deck was pretty much my limit), so if you're okay with the structure eventually being torn down/rebuild with an above grade foundation, my suggestion is to do termite treatments and try to get french drains/retaining walls as @lthenderson suggests to funnel any standing water out as well as you can, and keep an eye on it until you decide if it's worth getting it rebuilt with a decent foundation eventually.

No wood, no matter what it's rated/treated with/whatever is going to last without rotting if it's touching dirt. My deck was built out of pressure treated pine, and everyone around my area is shocked it lasted longer than 10 years. (NOTE: It was like this when I bought the house)

Adding the rocks is only going to make things harder in my opinion, because of what you are already seeing - they make it easier for decaying organic matter to collect and allows for weeds to grow, you can't actually mow/clean it easily, and the rocks are going to sink/migrate because nature is a constant and ground settling/buildup of debris/movement of the pebble/stones. You could try adding a containing border, but it's not going to really help in the long run as you didn't raise the structure, you just exchanged some of the existing ground level with the stones and the garage is still in contact with ground & water, and in another few years, there's going to be a good amount of dirt in the stone/rock border and you're back to where you started again, but having to dig out a bunch of stones to boot and deal with the occasional pebble projectile when you mow anywhere back there.

Termites (at least the subterranean ones I'm dealing with) can only survive in damp/darkness and they are drawn to rotting wood. They will die if they dry out (why they build mud tunnels) and if they are exposed to light as well. So the main things are: remove the damp, remove the darkness, and making sure they don't have direct access to wood (no attractive materials in contact with the ground).

And one of the things I also learned: termites are EVERYWHERE. Even if you got the immediate area treated, they'll still be in your yard, the neighbor's or down the street even. You'll want to treat your whole property to ensure that if they do come back to check out your house, it's not easy, and they'll start dying if they stroll through. I am DIY perimeter trenching my house/all of the deck footprint with Taurus (generic Termidor). I've done extensive reading on how to do it right, so I'm hopeful I don't have to deal with this mess for a least another 5-10 years.

I can't really raise the garage without replacing the slab. The slab is in 6 pieces, some bigger than others. The overall structure isn't going to fall down, but it's also not worth raising up and doing anything extensive.

I will look into Taurus/Termidor, thank you. Luckily, the garage is the only structure on my property that's high risk. The house is up several feet on cinderblock foundation. The fence has metal posts, and panels are easy to replace if necessary.

[lthenderson]

For the dropoff/retaining wall, I would just start laying pavers at the lowest point around your garage so that the first coarse is partially buried and keep adding tiers until it is high enough to contain the ground at the highest spot on the lawn side of the wall. The dirt you have to excavate between the wall and the garage could be used to backfill on the lawn side of the wall to even things up and make it flatter. You would have to so some reseeding but that is cheap to do. I can't judge the height of the dropoff to know what kind of safety concern it would be. I have seen many three and four feet tall with no railings at all and I don't think you are dealing with that much elevation.

For the area between the wall and the garage, I would excavate enough area below the slab to add a piece of water permeable landscape fabric, some crushed gravel, your french drain pipe, some more crushed gravel and then wrap the landscape fabric on around over the top. Then you can add a few inches of top soil and seed grass on top of that. The top of the soil should end up below the top surface of your concrete. Once the grass grows, you can mow it as normal and it still provides drainage for any water.

[BECABECA]

Yikes, I wouldn’t use termidor, it’s pretty toxic stuff. I’d treat the wood with boron, something like BoraCare. That penetrates the wood and protects it for decades, and is much less toxic. This is the advice that I got from my friend who owned the largest pest control company in Australia. He just mixed powder boron with water and sprayed it onto  all the wood of his houses when they were being built and never had a termite. For your situation, it can’t penetrate through paint, so you’d need to sand or drill holes to get it seeping into the wood.

[Sibley]

This sounds like a plan, thank you Ithenderson. I have scheduled the pest people for 7/3, so I've got until then to get as much done as I can.

Re drop off height - it's enough to stumble, but the location is also one where people shouldn't be walking. A foot, max. The cat will love it though (yes, will make sure she'll be safe from whatever the pest people apply). I might plant some sort of flowering plant rather than grass though, will research to find something that won't interfere with the drainage stuff.

BECABECA - additional anti-termite stuff is longer term decision. For now, have other projects. Like digging out rocks. And the inside of the garage is bare wood.

[SunnyDays]

Could you use those metal window well retainers?  I don’t know how wide they make them, but you would need several for sure.  Then you could just put in the drains they usually have and since your soil is sandy, the water should drain away.  Plus no rocks that keep sinking and anything that sprouts in there would be easily pulled out.

[Frankies Girl]

Yikes, I wouldn’t use termidor, it’s pretty toxic stuff. I’d treat the wood with boron, something like BoraCare. That penetrates the wood and protects it for decades, and is much less toxic. This is the advice that I got from my friend who owned the largest pest control company in Australia. He just mixed powder boron with water and sprayed it onto  all the wood of his houses when they were being built and never had a termite. For your situation, it can’t penetrate through paint, so you’d need to sand or drill holes to get it seeping into the wood.

I'm probably not going to explain this as well as the available research, but used responsibly, Termidor and other slow/non-detectable termite treatments are long lasting and will not harm beneficial wildlife. You absolutely could kill honeybees and fish and it may harm other things, but you'd have to be really careless to do this and there are plenty of other baits/chemicals out there that are just as harmful but not as effective. Fipronil - the is the main active ingredient - is also used in Frontline TopSpot, Fiproguard, Flevox, and PetArmor (used along with S-methoprene in the 'Plus' versions of these products); these treatments are used in fighting tick and flea infestations in dogs and cats.

Boracare is a protectant that is not rated for painted wood or soil treatment - just untreated/open wood. It needs to be absorbed into the pores of the structure to provide protection. It's definitely a good product especially for new builds, but for existing structures or soil treatment, it's probably not a great choice, and there may be difficulties trying to find something that is both effective and completely non-toxic to everything else but termites unfortunately.

I personally am just going to risk it and did LOTS of research on proper use of it as I live in a very termite prone area, and already dealt with two rounds of them. But I get that it not a great choice for some depending on where they live and their basic environment.

[Sibley]

Progress made, and question.

I've got most of the rocks out, and if it cools off a bit I might finish tomorrow. I'm sunburned, sore, and have the start of a few blisters, but oh well. I also got rid of the rock pile already, a neighbor wanted rocks and happily took it all. I think they took 10 wheelbarrow loads of rock, and what's left is probably another 2 loads.

On the front of the garage (not in the pictures above), I forgot that the slab angled so that the dirt/rocks and slab were all decently aligned. For consistency with the other sides, I want to have a "retaining wall", but it'll basically be sitting there just slightly buried. Should I place it at the same distance as the other sides? I would prefer to push the block as close to the garage wall as reasonable without causing bug issues. There will be flower bed on the other side of the block.

To satisfy curiosity: the south side will require a drop of 8-10 inches, the slab is sloping so it varies from front to back. I don't anticipate a problem. The back of the garage has a drop of between 4 and 8 inches right now, the slab slopes and also the dirt is really not even, so I should be able to smooth that variance quite a bit. I'm guessing 4-5 inches final drop. Also verified the presence of termites. Yuck.

[lthenderson]

As long as you have adequate drainage between the rock wall and the garage, the soil isn't touching the siding and you have room to maintenance that area, then there really isn't any set distance it should be between the wall and the garage.  By maintenance, I mean if you plant grass to leave room for a pass with a lawnmower or if you ever decide to run say a water line to the garage you have room to come up between the rock wall and the side of the building.

[Sibley]

Thank you @lthenderson , appreciate the input.