DAP 10.1 oz. Alex Plus All-Purpose Caulk - supposedly silicone non-drying

http://www.dap.com/product_details.aspx?BrandID=12&SubcatID=3

For use to seal sheathing/roofing, etc (why does this forum sometimes format the entire message as one paragraph? such a pain)

I think paragraphs are a function of the browser.

Do you use Internet Explorer?

It's cheap, but it's okay for interior. It will fill a limited size gap. I took care to use it within the stated guidelines and had the opportunity to observe it for about 18 months before covering it up and it didn't shrink or crack. However, that was entirely inside. Is it even specified for exterior? I don't think I would trust it in an exposed location.

On the exterior I found OSI Quad to hold up the best, although you need good technique because it is messy.

If you are going to metal or flashing in a critical location, I would use the Quad at a minimum or an even more expensive specialty roofing product.

I think it failed here. While caulks may not shrink, the crack often expands by a huge percentage in different seasons. A blower test done soon after caulking won't catch this. Consider tape or gaskets where possible.

OSI Quad (and probably many caulks) is "Not Recommended for Sealing expansion joints, including butt joints" or "applications less than 1/4" in thickness".

I've applied and monitored the Quad over three years in variety of demanding locations and it remains as my favorite all-purpose box store sealant. If you have a specialized application, I would highly recommend a specialty purchase, particularly if the quantity is more than a case. The DAP Alex is attractive only because it is cheap. I use it in the least demanding situations.

OSI Quad has the irritating quality where it will form bubbles when it gets warm, as we learned after using it around 40 windows during a deep energy retrofit. There are numerous references to this feature online, and the manufacturer "knows nothing" about it. Good product for places where it won't be seen.

For sealing sheathing to the studs on the inside of the cavity before I blow in cellulose. I see the link shows it as painters caulk. The website claims it is silicone and won't harden so I thought that would be good. Any good product recommendations for this? I might get the liquid nails. I don't anticipate it "moving" much (stud to sheathing interface)...

An adhesive applied before nailing makes sense to me. You want the sheathing to stay in tight contact with the stud and never pull away.

Jonr, framers are supposed to do that, but doubt they will, nd i cant watch them all day. So i plan to go in after and caulk the four sides of the cavity.

I wouldnt use it, especially for air sealing because of its rated movement at 12.5%. I would look for a class 35 or 50 product.

I agree. For best all-around use, a polyurethane or silicon sealant, ASTM C920 rated, with a high movement capability (class), good adhesion and long life.

For example: Dow Corning® 790 Silicone Building Sealant (+100%)

This is worth reading, especially the part about how a proper filet joint must use a bond breaker. At that point, you might want to just use a good tape (like Siga or 3M).

Don't count on canned spray foam lasting past the blower door test. It has very little movement capability.

Dow 790 is $13 a tube. That is extremely expensive. I am caulking between wall sheathing and the 2x6 studs, not exterior door sills and windows. I was planning to get 5 cases of 12 tubes. If I did this caulk that's $600 extra for caulk. If i spent that much extra on every product to build this home I'd go broke. I have to set a limit and $13 caulk, sorry to say, is outside that limit.

Maybe look into the Dap Dynaflex 230. I have been using that and I personally like it. Plus its only around $4 a tube.

GE II Window and Door is Class 50 (twice the DAP 230) and is $6. So is Tremco Dymonic 100.

Posted By Surfsup on 25 Apr 2014 08:14 PM
Dow 790 is $13 a tube. That is extremely expensive. I am caulking between wall sheathing and the 2x6 studs, not exterior door sills and windows. I was planning to get 5 cases of 12 tubes. If I did this caulk that's $600 extra for caulk. If i spent that much extra on every product to build this home I'd go broke. I have to set a limit and $13 caulk, sorry to say, is outside that limit.

Surf - if the areas being caulked are out of sight, just use Tremco's Acoustic caulking. Its a bit messy to work with but it remains sticky and pliable forever. Because its been used in Alberta for more then two decades, we run into it on renos. After all that time it will still stick to your hands and make a mess so you can be sure it will move with every movement the house makes without losing its bond. Pick up a small tube and play with it and you will soon see why almost ever contractor in Alberta uses it to air seal their poly barriers.

I still swear by one part gun foam and yes I read the article noted by JonR when it was first published. We aren't talking about wire penetrations and I totally agree with common failures of the foam in wire penetrations I believe most commonly because of failure of foam injection into the bore hole (think lacking roots). we are looking at a perpendicular joint of sheathing to stud and proper caulk sealing requires a bond break at the corner which I would challenge anyone to find an economical solution.

I have sealed 1/2 house stud bays with sealant and half with 1 part gun foam. Tested and retested with a thermal scan with no discernible difference in seal loss. The only difference was the enormous cost of the caulking and the low cost of gun foam. Acoustical sealant is great but 27lf per quart is expensive to 2000' of foam bead per can.

What's the ASTM movement class of spray foam? The ones I've used were very inflexible (compared to a good sealant) and likely to fail over time. Here is some interesting data about estimated lifespan:

0<10 YRS - Latex Caulk, Butyl Caulk
10-15 YRS - Acrylic Latex Caulk, Fire Rated Acrylic Intumescent Caulk, Acrylic Caulk
10-20 YRS - Urethane Foam Sealant – One Part and Two Part, Acoustical Sealant
10-25 YRS - Acrylic Latex Silicone Caulk
10-35 YRS - Silicone Caulk

I'd seriously considering skipping the sealants and using tape and films (MemBrain, ZIP sheathing, building wraps, poly, etc) or gaskets to create air barriers. If not, use a decent ($6?, > 50%) silicon sealant (most applications) and a bond breaker.

Another option for spray foam sealing is Great Stuff Window & Door. It remains flexible after cured and sticks to wood and just about anything. It should be able to accommodate structural component movement and expansion/contraction without cracking. It costs a little bit more than standard 1 part can spray foam, but should cost much less than caulk given its amount of coverage. A 12 oz can at the local Wal-Mart costs $4.27 and should provide >300 linear ft of ~3/8" bead at the stud-to-sheathing interface. I doubt that a 10 oz tube of caulk @ $6 would cover a tenth as much.

Posted By jonr on 27 Apr 2014 10:18 AM
I'd seriously considering skipping the sealants and using tape and films (MemBrain, ZIP sheathing, building wraps, poly, etc) to create air barriers. If not, use a decent ($6?) silicon sealant for most applications.

Well I am using Intelloplus (similar to MemBrain) as an internal air barrier. So you think I don't need to seal the sheathing/stud cavities? That would work for me! I do plan to install the intelloplus with extreme attention to detail.

With that on the inside and something (ZIP, building wrap, taped OSB, taped foam) on the outside, you have two good air barriers and I don't see the point in using sealant in the stud cavities.