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We have a stone surround to our fireplace. I have noticed stone/cement dust often around it. about a week ago this stone came loose when my son hit it with a toy car. I have now noticed at least one more loose stone. This surround goes up to the ceiling and I want to fix this and strengthen stone that has not yet loosened. I am not sure what to use and should I first remove all old cement? Thank you enter image description here

  • Is the dust fine like flour or coarse like bread crumbs? – Jack Jan 20 '18 at 16:08

I would not remove any of the cement, except for vacuuming and brushing to make sure the surfaces are clean so the stone can be glued back in place with construction adhesive. Keep the glue far from the edges so it does not show, should any try to squeeze out. Prop it in place until the glue dries, a day or two will do and it will stay.

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    If it’s “real” stone and is over my head, (goes up to the ceiling,) I’d want to know if all that “cement dust” is unique or signs of a trend...especially because she says there’s another one loose. – Lee Sam Jan 20 '18 at 9:40
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    This all depends on the texture of the dust. If it is very coarse, like chunks the size of bread crumbs and larger, it will be from the vibration of the toy or other repeated hit from something, whether it be from a vacuum cleaner or other random objects. In this case, timing is everything when this type of wall is built. When the cement is added to the wall to apply the stone, the longer it sits on the wall before the stone is applied, the weaker the bond. So most stones will be bonded well but a few may not. Vibration is the enemy of all masonry. No room to comment about finer dust here. – Jack Jan 20 '18 at 16:17
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    If a chid can hit the masonry and knock a piece loose, I don’t want to be near it. So you think the “dust” is from the mortar? – Lee Sam Jan 20 '18 at 16:37
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    I am certain the dust is from the mortar. When this material is installed, the whole wall is covered in tar paper, or should be, then expanded metal lath and skim coated with masonry cement everywhere the cast stone goes and left to set up overnight. The wall gets another coat before the stone goes on and the cast stone is stuck onto it. There are variations of the this method, but that is the gist of it. Long story short, the whole wall is covered in mortar (cement). – Jack Jan 20 '18 at 16:50
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    The nature of the dust will or may reveal a little more info, I have a question to the OP and her answer may fill in more details, should I get an answer... – Jack Jan 20 '18 at 16:53

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