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I am looking for ways to waterproof the bottom of my garage. Last year I removed a concrete dog run that the previous owner had. Now, the wood is directly against the earth (with everything melting toward the garage unfortunately). I may have to add on or replace the plywood underneath the boards due to rot.

This summer I am looking to rip off the bottom two boards (I am thinking circular saw depth adjusted to cut only the boards). I then want to waterproof the hell out of it as I will be fixing the grade, and possible adding garden boxes all around the garage (so I don't need it to look pretty per se).

I have no clue what material to use but what comes to mind is PVC siding, parging, etc. Should I apply a membrane prior to putting on the siding or parging?

Any suggestions on how to tackle this project? Wood siding on garage

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  • "Parging" is usually a concrete or plaster product and will not be waterproof.
    – FreeMan
    Mar 16, 2022 at 19:21
  • Got it! So that is off the table! Whatever is put there will likely be touching dirt. So maybe PVC siding with a membrane on the plywood underneath it or something similar to that. . .
    – Shinobii
    Mar 16, 2022 at 19:26
  • Is it possible to add some fill dirt and slope the ground away? Gutters on the building would help if not already there.
    – Gil
    Mar 16, 2022 at 21:29
  • Thanks Gil. I'll be fixing the grade this summer. Just got new eaves and will be getting new shingles shortly.
    – Shinobii
    Mar 17, 2022 at 4:39

2 Answers 2

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It's a garage, not a boat. You will not "waterproof" it effectively.

If it's just a slab with the frame bolted to it, you either fix the grade correctly (sloping away from the building from below the top of the concrete) or you jack the whole thing up and build a concrete block wall to set it back down on. One of those is a lot easier than the other, obviously.

I suppose the third possibility would be to replace the lower part of the wall with ground-contact-rated pressure treated wood. Doing that incompletely might buy you a few years. Doing it properly starts making the concrete blocks and jacks look reasonable.

Shoving planter boxes up against the building is another way to make it rot. You'll need adequate space for drainage and ventilation, and you still need the grade such that wood is not touching dirt (especially if you live where termites also do.)

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  • I contemplated jacking the garage, but sounds pricey and I'm not sure this garage will last another 10 years, just trying to maintain it until I can rebuild it. I'll definitely get some quotes though.
    – Shinobii
    Mar 17, 2022 at 4:43
  • There was a touch of sarcasm in the "jack it up and add blocks" comment, @Shinobii, however I think the sarcasm font isn't displaying properly today.
    – FreeMan
    Mar 17, 2022 at 11:40
  • No sarcasm at all. Jacking buildings to riase or replace foundations is done all the time, and if you are not going to correct the grade by lowering the soil below the present concrete, it's the right approach.
    – Ecnerwal
    Mar 17, 2022 at 12:42
  • Yeah problem is that the garage has sunk over the 60 years it's been standing. So I'd have to lower my entire backyard about a foot. I'm looking I guess for a fix that will protect the frame for at least 10 years.
    – Shinobii
    Mar 17, 2022 at 17:39
  • I'm now wondering about using Vinyl siding at the bottom and going below the slab (after wrapping the bottom with a waterproof membrane). Then back filling the dirt slopped away from the structure.
    – Shinobii
    Mar 17, 2022 at 17:40
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Circular saw. no. use an oscillating tool to cut the nails and pull the bottom two boards off. (see "how to install lap siding")

Membrane, repair if it's damaged.

Replace boards with, same type of wood, or engineered siding boards like Hardieflex pre-paint the boards before fitting them.

Planters? only use portable planters, not raised beds, don't allow stuff to become trapped between the planters and the wall.

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  • Great, I'll research this! Yeah I was thinking Hardieflex as well. For a membrane, should I use a paint on or a material one? Also, by fixing the grade away from the garage, I will have to go at least a board under ground. Is this a no-no?
    – Shinobii
    Mar 17, 2022 at 4:42

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