Brick chimney crown / chimney wash repair & protection question

Motorapido · October 2019

A brick at the top of my chimney -- the crown or wash component -- split a portion of its front face off, along with a little mortar. A pro chimney restoration company inspected it today, and recommended removal of the entire crown/wash top row of bricks, and either replacement with cast-in-place concrete (looks ugly to me in photos) or a very attractive hip and ridge copper chimney cap. My chimney includes a flue for the boiler and one for the fireplace. House is 90 years old. All the other brick on the chimney is in excellent condition as is the mortar. The chimney inspector says that miraculously, the tile liner appears to be fine from top to bottom on both the boiler flue and the fireplace flue. Of course, the copper cap, which extends out and covers the entire chimney crown / wash top surface and includes a drip edge, is very expensive (I know we don't discuss price here, but suffice it to say it is about as much 120 cases of domestic beer). Because the rest of the bricks on the top row crown are fine, I asked about an option to just repoint the mortar around the brick the popped off about 3/4 inch of its surface face, and then seal the exposed soft inside of that brick and the surrounding bricks with a breathable brick sealant, and check the top of the crown for any cracks in the coat of mortar that sits on top of the crown and seal up any cracks with pure silicone. The chimney company will be sending me an estimate for that approach, and they did not poo-poo that approach.

Am I going down a bad cheapskate path here, or is my more minimal approach effective in protecting the chimney from further damage? Luckily, you can't see this edge of the chimney from the ground, so I don't mind that there would be a partially cracked brick remaining after the work if I go the cheap approach.

I should say that I have always believed the most conservative brick preservationists who warn against any variety of water sealer for brick, including the newer ones that claim to be fully breathable, so I need some insight from you guys. I don't want to have them put sealer on any of the bricks, only to realize later that the sealer does more harm than good. I'm hoping Jamie Hall can opine on this issue. I respect his thought processes and scientific approach, balanced with practicality.

Jamie Hall · October 2019

if it's the brick itself that split, it's likely it had a crack and water worked into it and froze and eventually cracked it apart. Not unheard of. Not even uncommon. I like your general simple approach -- with two thoughts. First, if you are going to do anything with the cement/mortar crown at all, I'd seal any cracks which were obvious -- but I'd also tap lightly on the whole thing (don't be a gorilla) and, if there areas which are separated from the brick, break them out. Second, then get the whole thing wet -- including the new brick -- and put a new crown coating over it. If you can persuade them to put fiberglass threads into the mix, so much the better. But the underlying masonry must be clean and sound and at least damp.

I'm not really keen on brick sealants, unless they really are breathable. If any water gets trapped in the brick or mortar beneath them, it will eventually freeze and crack. Better to arrange the chimney top so the top two courses or so of brick project out a bit, so that water which gets on the very top doesn't run down the side of the chimney, but drips off the projecting edge. That may not be possible, depending on the chimney. Some were built that way, some weren't.

My thoughts, for what they're worth...

Motorapido · October 2019

Jamie, thanks for your response. Your insights are making me confident with my less costly approach. I'll have the chimney company check the integrity of the existing crown masonry top, add mortar around the brick that lost a piece from its face, and ask them to apply a new crown mortar layer after ensuring that the original is sound. This is a pretty good chimney company, so I figure they'll understand and comply with the request for fiberglass in the mix. I'll ask them to use a breathable sealer just on the top two row of bricks.

ChicagoCooperator · October 2019

I worked in masonry restoration for some years from the architectural end of it. I'm not a fan of the sealant either unless the brick is porous to the point of infiltration. Have you considered an aluminum cap? Might be cheaper than copper and as longer lasting (and needn't be green if that doesn't match your house as well). Another problem with the shaling brick could be mortar that is too hard - it's supposed to be the sacrificial element in the assembly. That said, brick does sometimes fail, but it's replaceable or repairable. You should be able to match the brick or pick something the coordinated contrasts if you had to do the entire crown (I agree with you on saving $ on it if you don't need do replace the entire course).

Brick chimney crown / chimney wash repair & protection question

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