We've noticed some water damage on a small 8 inch section of baseboard in our basement. See below:

mold or water?

what next?

zoomed out

I was going to remove the baseboard to look behind. Any other suggestions?

Worried it could be a hairline crack in foundation. Or issues with perimeter drain...

It's not an active leak, it's dry and wasn't visible to us for some time.

We've also been going through a cold spell in Vancouver, with 18 inches of snow and -10 degree weather.

On the outside wall, there is a hose connection.

Any recommendations on what to do next? Or ideas of what could cause this?


Update #1: We've cut a hole to peek behind. I didn't feel any moisture but I think I need to make a cutout lower. Looking for a contractor to help us out, but of course...Christmas tomorrow, it'll have to wait. How big of a section will they need to cutout? Guessing at least stud to stud. Then they'll have to fix the vapour barrier, insulation, etc.

Update #2: I've pulled out the insulation and drywall. It's clearly a weeping crack in the foundation. See below: enter image description here

Near-term work: Now we had a foundation expert look at it, he recommends we inject/fill and patch the crack.

  1. Does it make sense to repair the crack on the inside of foundation?

To allow him to do that, I'll need to remove a stud.

  1. Any tips for removing studs? I want to put them back in afterwards. Should I remove the drywall higher and just remove the stud at the top? Any risks when removing studs? I might need to remove two, so the guy can access the crack.

Longer term work: When the weather gets better, my plan is to look at what might be causing water issues on the outside. I'll scope the perimeter drain, see if it can be cleaned out, and possibly raise a slab of concrete to make it slope away from our home.

  • What's to the left of the stain? That's where the leak is coming from.
    – JACK
    Commented Dec 22, 2022 at 18:08
  • @JACK - Added a second photo. There's not much, it goes left another 4 ft to the corner. This is a back wall of the house. Commented Dec 22, 2022 at 18:33
  • rather than call a contractor why not DIY? Many of us have done similar repairs. Begin with a new question asking what to cut. Describe the wall in the new post, what's on the other side, mark off the studs, and include a pic. Take it from there. Save $$$, and learn something. Basements are great areas to begin. I start with a 4in hole-saw cut, easy to close off with cut-out if nothing found.
    – P2000
    Commented Dec 24, 2022 at 19:51
  • @P2000 - Thanks! So far it's been all my labour. I intend to do as much as I can and asking for advice also. Commented Dec 30, 2022 at 6:38

5 Answers 5


Repair this crack with a "concrete crack repair injection kit"


enter image description here

Manufatctureres provide great videos, but here's a summary.

Work from the inside, no need to dig outside.

  1. Score a .5in wide V channel at the existing crack, using a concrete chisel
  2. glue on the supplied injection nozzles
  3. cover the crack with the supplied sealant cement
  4. inject the epoxy repair glue

You may have to remove some studs to get behind them, but I think it's possible to just chisel or drill the stud at the crack so you can apply the sealant between concrete and stud.

Make sure you have the repair kit suitable for walls, not floors. The wall kit includes the injection nozzles.

To restore the drywall, you'll need to provide drywall backing. Alternatively you'll need to cut the drywall back another 3/4in on both sides so your new drywall panel is "half-on" the studs.

As is common in the Vancouver area, there likely was no insulation at the below-grade concrete foundation wall (yes?), but you can upgrade it.

For insulation you first apply a 1.5in or 2in XPS panel (not EPS) to the concrete, seal the edges with expanding foam all around, and optionally fill the rest with fibre-glass or rock wool. The XPS is your vapour barrier, and you should not apply another vapour barrier plastic sheet. This will improve the heat retention in the basement, but only proportionate to the total wall surface area of the basement. As you upgrade the basement in the future, keep adding insulation. If not, there's little point in insulating this small wall segment.

That said, the water damage could have been worse had there been insulation.

Image: https://www.homedepot.ca/product/sika-concrete-crack-injection-fix-kit/1000172324


For now it looks like just water damage and a relatively young one based on color.

However that can turn into mold pretty soon if you don't fix it.

It is impossible to say where the leak comes from so you don't have to remove the baseboards to investigate.


Thanks for the new pictures.

Probably a very small leak for now, just dripping.

Location, somewhere above the dark spot on the base board.

No cutting needed, but unmount the drywall by using magnet to find the screws or nails and take them out. Use utility knife and cut along the edges (all 4) off the drywall.

Drywall comes out in one piece so easy to put back on.

  • Thanks @Ruskes, we're looking behind now, haven't found the problem yet. Commented Dec 24, 2022 at 19:42
  • @stackunderflow see my update
    – Traveler
    Commented Dec 24, 2022 at 20:53
  • Ty! Posted another update, looks like a weeping crack in foundation Commented Dec 30, 2022 at 6:39
  • @stackunderflow, well you found it, thanks for update
    – Traveler
    Commented Dec 30, 2022 at 7:23

Looks like just water damage to me.

If it's a hairline crack, it could be anywhere that drains into that corner. Finding it may be a major project.

My own approach was to seal what I could find before burying the wall under insulation, then accept that small amounts of seepage we're still likely and use pressure treated lumber for my baseboards. If there had been a bigger problem I'd have put in a perimeter drain system before insulating, to try to catch any seepage and route it to a sump.

  • how much drywall, insulation, etc did you have to pull open? Commented Dec 24, 2022 at 19:43
  • I started with bare concrete so I didn't have that problem. The brief answer is that you probably need to find and expose the entire crack before you can seal it.
    – keshlam
    Commented Dec 24, 2022 at 22:37
  • thanks, I've posted an update. Exposed the foundation right to where it joins the door! Commented Dec 30, 2022 at 6:40

Looks like a typical dirty water stain to me and by dirty I mean it literally came from water in the dirt.

It looks like you have a finished basement so the first step is likely to remove some drywall from that area and assess your foundation. If there's insulation back there then it's quite possibly growing mold already.

You should probably leave the sheetrock off so that things can properly dry back there until you get a plan in place.

As for proper foundation remediation, you'll want to talk with some experts.

  • thanks... Yea I think we're going to have open it up more and call in the experts. Commented Dec 24, 2022 at 19:44

Looks like the sheetrock seem up the wall is effected. Dry within 24 hours is the only way to guarantee no mold. Guessing your sillcock froze which means ADDRESS IT NOW BEFORE IT THAWS AGAIN. Each time it freezes it will rupture more. Some insurance doesn't pay if the leak is more than 7 days old. This includes if it was underground and impossible to see. I had to go to federal court to get paid for a leak in my house and wasn't paid until 4years after a faucet broke upstairs and flooded 3 levels for a week. Do not delay. If it thaws tomorrow it could be running 5-10 gallons a minute for hour until you get home. And the discoloration could be fresh and stained from the material it leaked through. I'm a licenced contractor with 25years of experience. Don't use the contractor referral system that your insurance company has find a good contractor not a restoration company. Restoration companies staff is usually in their 20s, how can they know everything in a house with a year or two of experience?

  • Thanks @Sparks McGee! We're looking into it. I cut a hole to peek behind the wall and feel around for moisture. Insulation felt dry... But I cut above so I think we'll need to pull more drywall and insulation out to find the problem. Commented Dec 24, 2022 at 19:36
  • Posted an update, looks like a it's a weeping crack in foundation! Commented Dec 30, 2022 at 6:42

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