I have this long, but thin, crack on my outside brick wall and I was wondering what I could do to repair it myself (if it's even worth repairing). Winter is coming and I'm afraid it will get worse with frost/defrost. I have no signs of water infiltration inside. It's right under a window, if it matters.

Bought the house in June, previous owner never noticed it/didn't care.

First picture shows the length of the crack and second shows the wider spot (I'd say thinner than a dime)

Crack's length

Crack's wider spot

  • To the downvoter(s): what can I do to improve my question? Nov 3, 2018 at 20:16
  • 3
    I don't see a down vote but that crack would bother me. I see cracks in mortar all the time but where the bricks are cracked in a straight line I would want to find out if there is a foundation issue. I would want a pro mason to look at it.+
    – Ed Beal
    Nov 3, 2018 at 20:21
  • Is this a solid brick wall or brick veneer?
    – DJohnM
    Nov 4, 2018 at 5:37
  • Solid brick wall. Nov 4, 2018 at 12:20

1 Answer 1


Very unusual to have the crack extend through the brick. Usually, the mortar is designed to have less strength than the brick so when the wall settles it cracks staggering down the wall in the mortar joints only. That way, the mortar can be repaired without replacing bricks. (Finding bricks that match exactly will be difficult.)

Several possible issues: 1) settlement, 2) expansion, 3) bowing of wall.

1) Vertical cracks are usually caused by differential settlement. That is to say, as the load is transferred to the ground, the ground has soft spots that cause the wall to settle a different amount at different points along the wall.

When this happens the crack will taper. That is to say, the crack opening will get bigger along the crack. Also, one side of the crack will drop from the other side. Neither of these issues happened, so I doubt settlement is your problem.

If it is settlement, it would be so insignificant that it would not be “failure” (collapse).

2) As a wall heats up and cools down it expands and contracts. If the wall is on the south side of the house (the side with the greatest heat gain and expansion) or if the wall is exceptionally long, expansion can occur. Cracking will occur at a weak spot, like below a window, etc. where there is less support (strength).

If this occurs in solid wythe walls, it can crack through to the interior. Is it solid wythe brick wall and did it crack through to the interior? Does the crack extend through the foundation?

If the wall is a brick veneer wall, the backing support wall portion may or may not crack too. Is it a brick veneer wall?

3) If the wall is bowing inward or outward it could cause the wall to crack. Is the wall straight?

Regardless the type of wall, if water gets in the crack and then freezes, it will worsen (enlarge) the crack.

  • Thanks. It’s a solid brick wall facing south. I can’t see any crack from the interior. I will have to check the foundation. Nov 4, 2018 at 12:20
  • I haven't had time to look at the foundation yet. If the foundation is OK, how could I repair the crack? Of course, if the foundation is cracked too I will hire a professional to fix it. Nov 6, 2018 at 13:00
  • @SimonArsenault Don’t just look directly under the crack, look 6’ or so each way from the crack at the foundation. The crack looks like a “hairline” crack, not a structural crack. If it’s not “moving” (increasing in width) and is not cracked on the inside, you could just seal it up. Otherwise, you’ll need to replace the bricks and repoint the mortar.
    – Lee Sam
    Nov 6, 2018 at 16:04
  • thanks! I looked at my foundation and it is not cracked. The cracks is between 2 windows. Maybe it's a weak spot of the wall... I'll seal it before winter and monitor it every seasons. What do you recommend for sealing a crack so thin? Is silicone appropriate? Nov 8, 2018 at 20:58
  • @SimonArsenault Yes, a silicone caulk (sealant) should be fine for a temporary fix. It’ll be unsightly, but you’ll be removing it and the brick eventually for a final fix. Normally we’d recommend a concave to to the caulk joint, but because it’s so skinny you’ll never get (make) a concave finish. Make sure it’s sufficient to cover the entire crack so moisture can’t be “forced” in around the edges. It’s good news that your foundation is NOT cracked. Is the brick a veneer or full wythe brick wall?
    – Lee Sam
    Nov 8, 2018 at 22:07

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