# Best Caulk For Chimney Counter Flashing?



## WNYcarpenter

What do you guys use to caulk in counter flashing to an existing chimney?

I just finished a rubber roof repair around a chimney....Part of the maintenance was to re-point with new black aluminum counter flashing. I do this a few times a year, and caulking in the flashing is one thing I never look forward to.

After tuck pointing I had a few options when it came to the flashing joint. Mortar, mortar caulk, silicone, or Firestone EPDM lap sealant.

I feel like the mortar won't adhere to the metal and will crack. I don't like the work ability of the mortar caulk...I always seem to make a bigger mess and ruin a nice flashing job. Silicone can get messy too...I had lap sealant on hand.... it's fairly easy to control, matches the black metal and rubber details, and I prefer lap sealant over most other caulks on any roofs, rubber or asphalt. That's what I used though it's not it's intended use.

I'm comfortable with the finished product, but I'm curious what is preferred, and if Lap seal is acceptable.


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## jmiller

I can't imagine putting lap sealant on counter. Seems low viscosity for that.

We're big fans of Vulkem. If you tool it with a spit covered finger it looks nice.


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## 4 seasons

Geocel has a caulk made for this application. That's what I'd use in your situation. It will match the mortar usually.


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## WNYcarpenter

jmiller said:


> I can't imagine putting lap sealant on counter. Seems low viscosity for that.
> 
> We're big fans of Vulkem. If you tool it with a spit covered finger it looks nice.


There was no sagging...The lap sealant actually installed nicely! Though not the best product to use, I don't foresee any serious issues. 

I'll take you word for it......that's why I asked!


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## Waynegc

We have been using sika sealant that we buy for wedi tile substrate. Great product, seals to anything, works well to mid 30's. Not intended use but guns well and skins in about fifteen minutes.


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## jmiller

SIKA is the stuff in metal tubes at the box stores, right? Ugh, I'll look forward to finding that on a roof now.


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## XJCraver

Their may be better stuff out there, but I haven't found it yet:

http://www.sashco.com/hi/lexel.html

The only downside is that you can't get it off your hands, so wear some latex gloves when you tool it. It will stick to dang near anything, and I've yet to have it fail on me. I've quite literally applied it in standing water (don't ask...) and was amazed at what it did. I've been very happy with it.


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## Waynegc

Sika sealant we buy from our tile distributor. Have not seen it anywhere else.. About $8 for 10 oz tube. Great product.


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## world llc

sika 221 and L15 are good... these formula's are not found at box stores

also butex or other butyl calking

also have good results with urithane calks, but tough to find


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## OldNBroken

Sonoplast NP1. 

Ask ten guys, get ten different answers. :thumbup:


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## dakzaag

butyl works great and stays elastic for 30 + years, only draw back is that it is hard to find in colors besides white and black. 

Sonneborn has a verticle sealant mostly for block walls, but it is super flexible and acts a lot like butyl.

I have used silicon and others as well in a pinch, but nothing works like butyl. Usually find it in the gutter section.


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## roofer1eric

Firestone All Purpose Sealant is a single component polyurethane non-sag moisture-curing sealant. It can be use to caulk sheet metal, masonry, brick and concrete block.


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## 1985gt

2nd NP-1, that's about all we use. Comes in enough colors to match just about anything. 

It use to be spec to use black lap to caulk term bar,or counter flashing. there is a reason why they don't spec that any more. It's about useless on that application in 2 years.


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## OldNBroken

1985gt said:


> 2nd NP-1, that's about all we use. Comes in enough colors to match just about anything.
> 
> It use to be spec to use black lap to caulk term bar,or counter flashing. there is a reason why they don't spec that any more. It's about useless on that application in 2 years.


That is the nice thing about NP1...a HUGE variety of colors. 
I have gone back on jobs done years ago and am pleasantly surprised at how well it holds up.


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## 1985gt

Renegade said:


> That is the nice thing about NP1...a HUGE variety of colors.
> I have gone back on jobs done years ago and am pleasantly surprised at how well it holds up.



Yeah that is true, I have used another brand of caulking for a specific roofing manufacture that was an Polyurethane, it was even easier to tool and is a great product. Sadly it only comes in white, stone, and black and it cost something like 25 a tube. Needless to say we don't use it on any other projects unless they are this certain brand. Plus its probably made by someone else like all their other materials and just has one hell of a mark up.


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## kage

we must be old fashion..we still use mortar..


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## room2roof

We use NP1.

Charlotte Roofing, NC Roof Contractor, Roofers in Charlotte North Carolina, Roof Repairs, Hail Storm Restoration


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