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My wife and I noticed some warping in our cedar siding near the chimney. Any idea what could be causing this and what sort of repair might be needed? Here is a picture:

https://ibb.co/dH4zQF

  • Does the siding go behind the brick or stop at it, Whatever it does, looks like water damage and the siding needs to be isolated from the brick. – Jack Jul 9 '17 at 1:48
  • It stops at it. Any idea what needs to be done here? I had a few thoughts: 1) Do we need a stainless steel liner for the chimney? 2) There is a tree branch hanging above this part of the roof, which we were hoping to have cut soon. Could that be responsible? 3) We had a chimney cap put in earlier this year. Could that be related? – Ken Feyl Jul 9 '17 at 2:05
  • Still need to sort out what is going on with it. It looks like the chimney was added after the siding was run. Perhaps the siding was cut to allow the brick to lay tight to the subsiding, but nothing was done to treat the siding to keep the moisture from the end grain of the siding. I don't think scraping and repriming will be the fix. Do you know if the chimney was a later addition or original to the house? FWIW, rain caps and tree branches have no effect on what is going on here. It has everything to do with how rain soaked brick coexists with the siding. – Jack Jul 9 '17 at 3:32
  • Thanks for the reply. Sadly, we really don't know. The house was built in 1995 and we are the fourth owners. We do know that there were no permits taken out related to the chimney. What about the stainless steel liner for the chimney -- would that help? My wife was thinking that it could be moisture from inside the chimney leaking out and infecting the siding. However, on the other side of this chimney not shown in the picture, we do not see this type of damage. Would more pictures help? – Ken Feyl Jul 9 '17 at 4:15
  • It is a good chance it is original, I thought the house was older. Another question. Does the sun hit on one side of the chimney and not the other? – Jack Jul 9 '17 at 4:38
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I will give a bit of an answer on what I see. It looks like the siding is taking on the salts from the masonry cement. The brick gets wet during a rain, the cedar that touches the masonry cement wick up the moisture from the brick which always has minute traces of the salt in it from the cement. Check out efflorescence This is what looks like in on the faced of the siding to a degree. Then it may be just blistered paint.

This is why the question of, "is the chimney added later" If it is, then the masonry cement while it was being built, cannot be cleaned off, and is in direct contact with the wood of the siding. If the chimney was original, there is a good chance, if the builder did it the way it is supposed to, the brick was laid first and the siding was run to the brick, keeping the cement away from the siding, albeit very close still, but still not touching the way a later added chimney would.

As mentioned before, it may only need what a good painter can provide, scraping, cleaning, priming and finish paint. To do it so it does not come back for certain, would require the removal of the siding, a small piece of flashing set to the brick, enough to nail to the subsiding and over the brick just enough to cover what the siding may touch. caulk the flashing to the brick, and caulk the siding to the flashing. Paint it up. Good till the cows come home.

Another way to accomplish that is to cut the siding with a circular saw set to depth so it does it cut ONLY the siding. The cut can be made as close as 1 1/2" from the brick, eliminating the need to replace the siding. The flashing mentioned earlier, now needs to be wide enough to go under the edge of the cut siding, and still reach the brick. After that is set, cover it with a piece of trim thick enough to have the face of the new trim just a little in front of the thickest part of the siding. Perhaps 1" thick...

This has become more than a bit......

7-9 edit

To elaborate on the comment about the sun on the west side. The sun will draw out the moisture more rapidly on that side and therefore, expedite the depositing of salts on the surface of the siding. It goes like this, the brick gets wet and with that the salts in the brick or masonry cement, in trace amounts get sucked into the end grain of the wood siding. when that occurs, the siding swells which will start hairline cracks in the paint. This allows the moisture to get carried through the grain, and evaporate through the crack in the paint. This helps push the paint off the surface of the siding and make it bubble. The salts traveling with the moisture are deposited behind the paint as well as some leech out through the cracks in the paint too.

This is repeated each time the chimney gets wet from rain or melting snow and compounds the deposits formed the brick. The sun drawing it out on the one side more readily makes it even worse. In masonry, moisture is always seeking equilibrium, as the sun dries out the surface, the remaining moisture within the chimney moves toward the dry area, but since it is drying out faster than the other side.... Well I hope you see the point I am trying to make.

  • Jack, it sounds like you nailed it. One question: what about caulking without flashing? Would that work long-term or is adding the flashing a necessity? We are probably looking for a longer-term solution than just repainting. I don't recall having seen the water damage during our inspection in January, so I fear that this happened rather quickly and would repeat itself if we just repainted. In any case, many thanks, and we will be sure to post pictures once this is all done (it may be a few weeks). – Ken Feyl Jul 10 '17 at 3:24
  • It needs the physical barrier between the brick and siding. metal is a sure way for that. Caulk will be a hit or miss proposition since there will be no way to know if it got in far enough to create a barrier. The biggest fear for me would be to create a gap big enough for caulk to do the sealing as you mention, and that process of creating the space destroys the barrier under the siding, whether it be Tyvek, tarpaper, or what have you. Opening up the wall the way I suggest allows that barrier to be repaired with the flashing. – Jack Jul 10 '17 at 3:36
  • To add about the importance of the tarpaper barrier, If the caulk failed which is there to protect the siding, then the sheathing under the siding would also be vulnerable. Don't let an easy fix potentially do harm over the long run. – Jack Jul 10 '17 at 3:39
  • Jack, it sounds like it's not worth cutting corners. We'll do the flashing. It may be a few weeks, but I'll report back with pictures once it's done. – Ken Feyl Jul 10 '17 at 3:44

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