Caulking Help!

s219 · Jan 6, 2014

I am finishing up my generator shed (full details to come) and put on an exhaust chimney yesterday. It's a typical arrangement that would be used for a gas hot water heater or furnace, with a metal cone, pipe, storm collar, and cap, all galvanized steel. I caulked around the cone/pipe joint and collar/pipe joint yesterday afternoon when temps were mild. I used DAP Alex Plus caulk, which I have had great luck with over the years.

Well, rain arrived earlier than expected last evening and has been a lot heavier than expected (I should not be surprised -- we've gotten swamped over the last few weeks). This morning I see that the caulk has partially washed away and run down through the joints along the pipe and is dripping inside the shed. Obviously it never had a chance to tack up at all.

It's supposed to rain all day, as temps drop from the 50s to single digits overnight. I am thinking I will try to wipe up all the wet caulk when I get home from work this evening, before the mess freezes up. Then we have a couple days well below freezing, then warmup into the 40s on Thursday just in time to bring more darn rain.

Any suggestions for a caulk product that I can apply which will be more rain resistant? Looks like my next opportunity to caulk in above freezing weather will be Thursday with temps in the 40s, but "chance" of rain moves in that evening and exists for three days after that.

I can possibly throw a tarp over the chimney to try and keep it dry, but who knows if that will really protect it enough if we get heavy rain again.

ray66v · Jan 6, 2014

Sounds like you used "B" vent, double walled pipe?

They make silicone in silver color, for calking galvanized pipe.

I recently bought some at Lowe's.

You can use any color you have.

Latex calk should not be used for anything, other than sealing gaps in wood.

/pine · Jan 6, 2014

You're sealing roof penetrations with calking?...did you use vent/pipe stack boot flashing's?

Hard to find a sealant that works in really cold WX...you might find some self adhesive rubber roofing patches...or some scraps of torch-down bitumen roofing...(can be applied with small propane torch)

randy41 · Jan 6, 2014

the caulk doesn't cure very fast when its cold out. i use the plastic roof repair stuff. the black gooey stuff. it works best when its warm out too.

Baby Grand · Jan 6, 2014

^ copy what randy said.
Make sure you wear clothes that you don't mind getting black smudges on.
That stuff is worse than the silver colored anti-seize stuff.

Boot flashing, as /pine mentioned, will make the job a long term survivor.

Look forward to seeing what you came up with - will there be pictures?
We have an old dog house that I've been thinking would just about fit over the Trailblazer.
Do you need to vent it so it doesn't overheat?

s219 · Jan 6, 2014

/pine said:
You're sealing roof penetrations with calking?...did you use vent/pipe stack boot flashing's?

Yes, there's a boot that was lapped in under the shingles. The only places needing seal are the joint where the pipe passes through the boot and the storm collar that sits right above that. Very small gap really.

s219 · Jan 6, 2014

ray66v said:
Sounds like you used "B" vent, double walled pipe?

They make silicone in silver color, for calking galvanized pipe.

I recently bought some at Lowe's.

You can use any color you have.

Latex calk should not be used for anything, other than sealing gaps in wood.

Yes, double wall.

tcreeley · Jan 6, 2014

Get your flashing right. I use silicon caulk- even below freezing- works fine, water resistant. Use hi-temp silicon caulk for metal chimneys.

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s219 · Jan 6, 2014

Baby Grand said:
^ copy what randy said.
Make sure you wear clothes that you don't mind getting black smudges on.
That stuff is worse than the silver colored anti-seize stuff.

Boot flashing, as /pine mentioned, will make the job a long term survivor.

Look forward to seeing what you came up with - will there be pictures?
We have an old dog house that I've been thinking would just about fit over the Trailblazer.
Do you need to vent it so it doesn't overheat?

Yes, I have tons of pics with all the work, including electrical and fuel. This is a water cooled diesel unit, so we have one large vent louvre lined up with radiator outflow, then another in opposite corner for inflow. Plus, heavily vented soffits for general ventilation.

/pine · Jan 6, 2014

s219 said:
Yes, there's a boot that was lapped in under the shingles. The only places needing seal are the joint where the pipe passes through the boot and the storm collar that sits right above that. Very small gap really.

OK I understand now thanks...

I recently had to wait on the weather to replace a skylight dome because of the (sealant) curing temperature required...it should be listed on quality sealant tubes...

in a pinch where regular calking would suffice (heat wise etc)...duct tape can be used...I used it to make temporary step flashing ...(and it sticks in cold weather)...

good luck...

s78wingrider · Jan 6, 2014

Gutter caulk!

Midniteoyl · Jan 6, 2014

I used this for the wood stoves both in my house and garage.. They have it in black or red (red is ugly, but higher rated) too.. Sets up quick and has held up outside for 9 years so far.. 76 Rutland High Temperature Black Silicone Fireplace Sealant 10 3 FL oz Tube | eBay

It can be found at Ace.

Midniteoyl · Jan 6, 2014

As a aside: I painted my pipe showing above the roof line in high temp BBQ Black, Satin and used the silicon over that. Looks great and is still sticking.

s219 · Jan 6, 2014

I found a tube of flashing & gutter caulk that has a 3 hour "rain ready" time, so I think I will try that. I remember using gutter caulk in the past, and it is some seriously goopy thick stuff that skins over quickly. I also bought a tube of black roofing sealant that I can use to hold down the edges of the shingles that overlap the flashing.

High temperature is not a major concern (I think) since the double-walled 4" chimney pipe is really just acting like a non-combustable "tunnel" for the 2" exhaust tubing that will go up the middle of the stack. I plan to leave a ~1" air gap around most of the exhaust pipe, but might stuff a wad of fiberglass insulation in near the top of the chimney to cut down on possible rattles and to seal off the opening.

I was able to scrape and wash off the DAP caulk with hot water fairly easily tonight, though it wasn't fun in cold temps with the wind howling. It had started to skin over in some areas, but was still wet in others. It had left some milky drips down on the generator's muffler below, but those wiped up pretty easily.

Thanks for all the input guys. Live and learn!

/pine · Jan 6, 2014

Polybutylene caulk (what I think is being referred to as "gutter calk") can be applied below 40*...not sure it will cure at lower temps but is a good suggestion...
Regardless...be sure to check the seal when weather warms...

Midniteoyl · Jan 7, 2014

s219 said:
I found a tube of flashing & gutter caulk that has a 3 hour "rain ready" time, so I think I will try that. I remember using gutter caulk in the past, and it is some seriously goopy thick stuff that skins over quickly. I also bought a tube of black roofing sealant that I can use to hold down the edges of the shingles that overlap the flashing.

High temperature is not a major concern (I think) since the double-walled 4" chimney pipe is really just acting like a non-combustable "tunnel" for the 2" exhaust tubing that will go up the middle of the stack. I plan to leave a ~1" air gap around most of the exhaust pipe, but might stuff a wad of fiberglass insulation in near the top of the chimney to cut down on possible rattles and to seal off the opening.

I was able to scrape and wash off the DAP caulk with hot water fairly easily tonight, though it wasn't fun in cold temps with the wind howling. It had started to skin over in some areas, but was still wet in others. It had left some milky drips down on the generator's muffler below, but those wiped up pretty easily.

Thanks for all the input guys. Live and learn!

The Hi-Temp wasnt a concern for me either, I just found that it was really high quality caulk..

EddieWalker · Jan 7, 2014

Never use painting caulk to attempt to seal flashing.

My favorite brand in Henry, which is sold at Home Depot. It costs twice the amount of good quality caulking, and it's worth the price. There are a few other good brands that are clear, but if you want the very best, it's grey in color and pure misery to work with. It sticks to everything!!!! Once you get it on yourself, good luck getting clean. LOL

Eddie

ultrarunner · Jan 7, 2014

Roofing mastic and flashing caulk are about the only times I will put on disposable gloves.

It makes it so easy to manipulate without the mess and then dispose into to bag with no mess.

/pine · Jan 7, 2014

I have an old friend that likes to say (about getting roofing tar etc. smeared on himself even when being judicious)..."that he can just walk by it in a store and he will have it all over him"...