My garage was built quite a while ago, and the belly boards need some fixing. They are either seeping moisture into the garage or leaking from cracks. I'm wondering if people think I should replace the boards entirely or try to seal them up with more material over them?

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This side of the house the board is below the sidewalk a bit. The boards closer to the door (in the pictures above) have started to bulge, there are large gaps at the tongue and groove where they fit together. I sprayed some foam in the visible gaps to stop rats from getting in and prevent any leaks (the yellow foam can be seen in the shot, it's sort of faint). There is moisture seeping into the garage still though, when it rains hard, some new plywood siding I put up inside the garage is starting to look moist down towards the floor.

The other side of the house is worse I think. No visible gaps, but the boards are super worn. I recently cleared out a ton of brush on this side, there were two large butterfly bush trees wedged between the garage and fence that I took out. I think these boards are also seeping moisture into the garage (might start leaking more now that I took the trees out).

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Should I for sure go to the trouble to replace the boards? Seems like it might be doable to seal them up with more material, and that the job would be easier.

Update 4/28/2020

I ended up purchasing some white aluminum siding and slid it up under the siding as recommended by Ed Beal, also sprayed a bleach solution as recommended by JACK beforehand. Thanks for the recommendations guys!

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    I would get some flashing and slip it under the siding. I would remove the bottom screws slip the flashing up and use the original screw hole for a new screw with a washer. Possibly a longer screw to make sure you have a secure washer. I use washer sealed screws any time I am working with metal siding or roofing. – Ed Beal Mar 28 at 14:30
  • Thanks for the suggestion Ed! I'm wondering if you could recommend which type of flashing to use for this fix? – pauwlsky Mar 28 at 19:47
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    I purchase rolls of galvanized metal or aluminum at my lumber yard. It comes in different widths and lengths I would get it wider than the 2 boards and slip the extra up under siding. If the garage is longer than a roll I over lap them a couple of inches. If the siding is tin I use galvanized, if a wood product aluminum for wood or cement siding I don’t want dis similar metals and aluminum is cheaper. You can also find the rolls on line to get an idea of price. – Ed Beal Mar 29 at 0:46
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Seeping moisture or leaking from cracks, either one is not good. Yes, sealing and or patching will be much easier but it's something you'd have to do every year as the problem gets worse. If those boards have been exposed to moisture over the years, they are probably starting to rot from the insides.

Give them a good pressure cleaning and check them out more thoroughly. If they appear to be in good condition, I'd think about covering them with one of the many roofing membranes that are out there. If they show signs of rotting, then starting to replace them will be your best bet.

  • Thanks for the suggestion! I'm leery to pressure wash the boards, just because I don't want to blow a bunch of water where it could be trapped between the belly boards and the new interior siding I put up. I skirted perimeter of the garage this morning and pushed a claw into the belly board (also pressed into it with a small metal rod) to probe for rotted wood. Surprisingly the wood isn't soft in any areas, which makes me think it should still have some good integrity? I think the boards have been treated heavily since they smell like creosote, so perhaps they are still good? – pauwlsky Mar 28 at 19:35
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    @pauwlsky OK then, maybe just spray some bleach on them to clean them up before doing anything else... pressure cleaning might be bad with the interior siding. – JACK Mar 30 at 12:09
  • Oh yeah, that's a great suggestion, I will do some prep with bleach to get rid of any fungus that might be taking root. Also, in regards to using the membrane roofing material, which material in particular would you recommend? In my experience it's difficult to purchase PVC in small amounts, and you usually have to buy enough to do a large job. – pauwlsky Mar 30 at 20:53
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    On one of my jobs, the wood was higher and I used double rows of regular shingles. Looking at this more closely, because it's appears to only be about 6 to 8", I like Ed Beal's idea of using the flashing. You can get it in different sizes so you wouldn't have to cut it as you would with any rolls of rubber roofing membranes. – JACK Mar 30 at 21:56

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