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Question DetailsAsked on 1/6/2016

How do we permanently stop the brick and/or mortar on the floor of the front porch from "leaching" white residue?

Brick/mortar is approximately 2 1/2 years old and problem did not start until 3 months ago. Area catches the afternoon sun and residue appears to occur where direct sunlight has hit. Have used plain water; soap and water; white vinegar (both diluted and un-diluted) which has stopped the residue for a short time but it again re-occurs.

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2 Answers


What was originally done that it lasted 2 yrs 3 months before the problem presented itself? I know the builder who did our house washed the bricks with some solution but dont know what it was.Two years at a time is way better results than what you've had recently. Seems like an odd problem to have but then I am pretty much an indoor person. It could be happening here at my house and I just am not aware of it. Good luck finding a lasting fix to the issue!!! Peggy

Answered 4 years ago by PMiller


Unless you have very poor quality bricks, what you are seeing is lime water leaching out of the mortar - and this will occur whenever it has gotten wet then dried out, because as the lime water evaporates at the surface it leaves a lime coating, which when it dries is basically a thin limestone layer.

White vinegar or spray Lime Away can remove it (use in moderation without soaking the mortar, as it eats mortar too) - heavier buildups require sponging with muriatic acid (dilute hydrochloric acid, which is probably what the other commenter was talking about) to remove it - it is also used for initial cleanup of lime and cement on the brick surface after construction.

Stopping it - general sealing of brick is not recommended, because water gets in through sealcoats through scratches and pinholes (especially in walked-on surfaces) but cannot evaporate back out the same small openigns, so the brick stays saturated and the mortar and bricks (if not fully-fired firebox or porcelain bricks, which they VERY rarely are in house construction) gradually soften and break up.

One thing that can be done - differences of opinion on this, but has worked for me both in outdoor environments like yours and on floors that get frequently wet-mopped or frequently get and stay wet (like entries and mud rooms) or are wet-cleaned by machine, is using a tile grout sealer hand-brushed ONLY onto the mortar joints, leaving the bricks uncoated to allow evaporation. Will still form a limited amount of laittance (the lime buildup) but can reduce it dramatically.

Another thing sometimes done for this is grinding or gouging out the top 1/8-1/4" or so of the mortar and replacing with exterior/floor sanded latex modified tile grout, which wears better, is more water resistant, and does not leach out lime anywhere near as much. This is a common fix for deteriorated brick floor mortar joints, but does look different than normal mortar if done as a spot fix.

One possibility here - is that normal house bricks and mortar were used (as they commonly are), instead of "lay" or "floor" bricks and latex modified cement mortar. These are a much stronger brick and a harder mortar (more like tile mortar) that do not soften and leach out nearly as much. Of course, too late to change that if that is the case.

Answered 4 years ago by LCD

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