Sandstone chimney

[Chuck52]

In 1956, the fella who built the house I now own thought sandstone would make a nice chimney material. He was right about the interior part of the chimney.....it looks great. However, here in the middle of Missouri it rains. Sandstone is porous. Very porous. Whenever it rains long enough or hard enough water finds its way down into the house. The chimney cap is in good shape, we have copper flashing mortared into the stone, and I've repaired the mortar joints in the chimney, and still water gets in unless I have used a water proofing material within a year or so. I've used the oil based and silicone based spray on solutions, and both seem to work for a year but I'm getting to the age I'd prefer not to climb up on the roof any more than necessary. So, I'm looking for a longer term solution. I thought the newer silane/siloxane solutions might be the answer, but then I read where "silicone rubber" might be better. I'd prefer not to change the appearance of the chimney too much, so a clear material would be my choice unless there's just no good one available. What's my best bet?

Thanks for any suggestions.

Chuck

 

[Egon]

Keep a fire going on a regular basis!

 

[wrangler6831]

Have you looked into clear EPOXY paints. We used it on a garage floor and it didn't change the color and it's supposed to be waterproof. But I'm not sure how it would work for your project.

Rich

 

[mjfox6]

I would not use an epoxy product for a chimney, they will not breathe. I'd use something more like this:
ChimneySaver Water Repellent

 

[Chuck52]

ChimneySaver is a siloxane type material. I will probably go with it or something like it unless I hear of something better. There are a number of companies which make this stuff, with perahps differing concentrations of silanes and siloxanes. I was hoping someone had direct experience with something similar to my little project, but I bet most folks know better than to use sandstone in a chimney!

I guess allowing water vapor to diffuse out, like the silane/siloxane things is a good idea, but I'm about ready to seal this thing up any way I can. I've even thought about building a metal box around it using raised seam roof metal or something. However, the thing is about 8' x 2' x 5', so we're not talking a small job.

Thanks for the responses....even Egon's, which presupposes a climate like his own?

Chuck

 

[Egon]

We have one exterior brick chimney [ dual tile lined flues] that has a lot of spalling bricks on the outer cladding.

One flue serves the oil fired furnace water heater and the other was for the original open wood burning fireplace. Previous owners had a propane insert installed which we removed and replaced with a wood burning insert and a 6 in. stainless steel chimney liner.

From what I gather the spalling was caused by a previous owner using a sealant on the brick. Some moisture would still get through the joints to be adsorbed by the brick. When heated the moisture turns to steam and breaks off the outside of the brick. Freezing may do the same??

At this time the spalling has almost stopped.

I've been meaning to repair the chimney but still got to do the actual work.

My thoughts were that the odd fire may dry out the stones.

 

[Chuck52]

Ah, Egon, now I see your logic! I wish I had a brick chimney, even if it needed repair. I'm not, and never will be, capable of replacing my sandstone chimney with more suitable brick. I don't even like to think about what a mason would charge for that job. That pile of sandstone looks really nice from the ground, but when you get close it is clear that it has degraded considerably over the years, mainly from the freeze-thaw cycle, but probably also just wind and water abrasion of the soft stone. At this point, I merely hope to slow down the decay until it can be a problem for my heirs.

Chuck