I was looking at a house and couldn't help but notice that literally all the external bricks were covered by small holes, most of them filled with what looks like a kind of resin:

Picture of weird holes in external walls

I'm new to the country (Australia) and I've never seen anything like that. It's definitely not caused by frost, since the minimal temperature in winter is about 8° C (46° F) and nobody I asked remember having seen snow in the area.

Many people told me they had already seen this, but no one was able to tell me what it was.

My questions are:

  • What is this?
  • Is this a risk for the house on the long term?
  • Is there something to do or to worry about it?

2 Answers 2


I suspect that the material is a lot closer to glass than resin, and is part of the "look" of this particular style of brick - that is, it came out of the brick kiln that way.

It might or might not be manganese. One of the potters I know is prone to using a light clay with manganese, which does get brown specks, but they are smaller - however, that's "pottery clay" not "brick clay" and perhaps they are smaller due to using smaller bits of manganese. Otherwise very similar in "look."

Closest I've found in a quick look is "light ironspot" - still looking for a decent picture. Name would suggest iron ore rather than manganese for a material.

In short, nothing to worry about.

  • Yes, it could totally be glass, but somehow I assumed it has been added after the house was build, so I didn't even considered it as a possibility. If I understand correctly, this is a part of the brick that melt during the brick's cooking process? Anyways, thanks for the confirmation this is harmless to the house! :o)
    – LeFauve
    Commented Nov 18, 2014 at 2:16

That's almost certainly an ironspot brick. It's a decorative effect.

enter image description here

  • I'm not 100% sure I should trust a house where builders used pavers for walls :o), but thanks for the confirmation!
    – LeFauve
    Commented Nov 18, 2014 at 2:13
  • 2
    It's not pavers - it's "architectural brick" and probably had a significant upcharge at the time of building over standard brick.
    – Ecnerwal
    Commented Nov 18, 2014 at 2:38

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