Caulk advice

Looking for advice on caulk types for exterior applications (around windows, doors, and trim pieces). I've been DIY-ing for years but have just noticed a couple of things about silicone caulk I've installed. On a garage I built just 3 years ago, 100% silicone paintable caulk (GE) seems to have shrunk back enough to be noticable in nailholes, edges of trim, and around windows. Also noticed recently that some brands of self-adhesive window flashing say not to apply over silicone caulk or not to use "solvent-based" caulks.

So now I'm wondering if 100% silicone is always the best choice. The other choices seem to be "siliconized" acrylic (water-based) and just plain acrylic.

 

IMO, and you know Marksr will be along shortly with the good advice, Silicone is never a good exterior product. Sun and weather take it's toll on it. I prefer to use an elastomeric caulk where two planes collide, such as at brick mold or window molding. Let's wait on Mark to chime in here.

 

You meant not paintable, right?

Elastomeric or polyurethane caulks would be best although they can be a little hard to find in small towns. A siliconize acrylic latex caulk would be bare minimum.

 

I have to agree Marksr is the man.

No, GE makes a paintable 100% silicone GE Silicone II Paintable Silicone Is Rain-Ready in Three Hours. Other than the shrinkage bit it seems to retain flexibility and doesn't flash paint even painted within an hour or so. I don't know if it will outlast the house . . . (liftime guarantee).

I have some trim (battens) on my house that I sealed a few years ago trying to stop rot behind them, I'm pretty sure (I really sure write this stuff down) I used plain old Alex Plus (acrylic with silicone). Now I'm trying to remove the battens to replace the siding and it's like they're glued on at the edges, plus it seems to have retained flexibility.

Anyway, can you say anything about the reasons for your prefs above? I'd like to know something about which type to use where and what might be available at big box stores?

Sealing trim, especially around window frames, I need something paintable. I'm not familiar with either polyurenthane or elastomeric although I think I've seen the latter somewhere. It's always struck me as a description rather than a type of caulk. Are these guys water-based?

 

Just searched Lowes and they have nothing called an elastomeric caulk. Paint and roof patch are elastomeric but not any of their caulks. At Home Depot something called Sonneborn NP1 Gun-Grade Polyurethane Sealants turns up and DAP Flexible Clear Sealant, which is paintable.

 

It's probably been 10 yrs or so since I've had the displeasure of using Alex Plus. IMO it's one of the worst caulks available. It didn't use to be siliconized so maybe they've improved it some.

Elastromeric is a type of caulking and cleans up with water. Polyurethane caulk cleans up with paint thinner. Both adhere and hold up better than latex caulk. The Sonneborn should work well for you.

 

Thanks, I'll check it out. What is the problem you guys have with 100% silicone for exterior use? I could swear it was recommended to me in this forum, possibly in the windows and doors group, a few years ago. Also to seal nail heads/overdrives with a dap of silicone, which I'm a little disappointed in the results of.

Not that I expect everyone to agree with everyone else . . .

 

Hi, I installed my replacement windows about 5 years ago Vinyl to Stucco. I used Side Winder by Dap its a polymer, cleans up with thinner. It realy worked well. I live in a very hot part of Ca and the caulk has not checked or cracked. It is Paintable. You may want to give it a look.
Good Luck Woodbutcher

 

If you are caulking to fiber cement siding (judging by your other threads, I wonder) you need to use a sealant that is recommended for that application. I primarily use OSI Quad on all my fiber cement jobs.

 

Yes, fiber cement also, but windows in T1-11 siding also that I just finished siding and need to seal.

I'm trying to switch over to something better for general use and have good knowledge of what each is usable for. Yes I've seen the Hardie cautions about caulks. Thanks for note!

 

At first I was wondering if you guys couldn't say brand names but now I'm seeing you're mentioning some. One problem is neither type marksr mentioned turns up when you search on caulk - they are sealants. What's the difference anyway?

The only "elastomeric" I'm finding that doesn't seem to be a concrete repair stuff or mobile home roof goo is Dap 18376 Elastomeric Indoor/Outdoor Clear Sealant. Then there are a few like GE GE29000 Infinity Premium Acrylic Sealant Caulk that do not have elastomeric in the name but say they are elastomeric in the description. But the GE is acrylic and acrylic is bad I'm hearing.

So can you give me some clues on elastomeric products I should look at? If it's water based and works, it sounds nice to know about.


I've found several polyurethane sealants (also NOT called caulk)available:

• OSI QUAD sealant
• Vulkem® 116 Sealant - Tremco Commercial Sealants & Waterproofing
• Geocel 3300 polyurethane roofing sealant
• Sonneborn NP1

I'm also noticing another type of sealant that Woodbutcher mentioned - polymers.

 

I don't know for sure but I think some manufactures call their caulking a sealant to differentiate it from the common run of the mill caulks. IMO it's caulking if it comes in a tube the inserts into a caulking gun - no matter what they call it

 

One elastomeric product I have used and like well is Big Stretch. Comes in colors as well. Does not crack, and as it's name indicates, it stretches pretty good.

 

It's good to know I don't need a specialized "Sealing Gun".

Interestingly Sonneborn calls NP1 an "elastomeric polyurethane".

 

And to go back to silicone, manufacturers seem to tend to specify 100% silicone for windows. Here's a quote from a Fine Homebuilding article: To comply with most window manufacturers’ warranties, be sure to use a window and door silicone caulk that has an ASTM C-920 rating on the label.

I'm working on old windows so warranty isn't an issue and if you guys say polyurethane is better for exterior sealing I'll go with it.

But other than the slight shrinkage that I noticed on my own, I still don't know what it is about silicone that you don't like. Going by what manufacturers say, the claims on the labels for silicone seem to be about the same or better than what it says on polyurethane (permanent and stays flexible).

What's the advantage of polyurethane or elastomeric?

 

Silicone will degrade in direct sunlight. It doesn't have the stretchability of other products. You can't paint pure silicone.
Elastomeric won't degrade in direct sunlight. It has excellent stretchability over silicone alone. It is paintable and provides easy water clean up.

 

Just to note...since I finally read this.

What marksr used 10 yrs ago was probably plain ALEX caulk...and it pretty much did suck. It was a straight latex acrylic. Dried out and got hard and crumbly when exposed to weather. I thought it was ok for some interior applications, but it WAS the cheapest stuff you could buy. I used Alex Plus to fill in cracks and such on the rafters of our porch here, before we repainted the ugly blue the prior owners used. Purely for aesthetic reasons and it works just fine. Note...no weather or sun on those areas. I've also used it inside for various reasons and have been quite pleased. The ALEX Plus is much better than ALEX, but there are better products out there for exterior use on windows, doors, trim, and such.

 

Most caulks will say they meet ASTM-920, they don't necessarily have to be silicone. If it doesn't, it's probably simply a cheap "painters caulk" that you should only use on interior work. IMO caulk and sealant are almost interchangable, but in my mind when one talks about caulk it can be interior or exterior, and it usually is done for aesthetic reasons (like painters' caulk). Sealant is a word that in my estimation carries more of an idea of permanence, adhesion and water resistance, which is almost always something you want in an exterior setting. Whether that's true in all cases or not I don't know. I think its psychological marketing in a way. I would rather use a "sealant" on a roof that could leak than a "caulk". Or a window... or a driveway. And in most cases I think that's the case. Urethanes are more permanent, seal better -and are harder to remove- than other types of caulk, but they have limited ability when it comes to stretching. Some of the products you listed, however, I wouldn't use for caulking trim- the Sonneborn NP1, for instance. That's almost exclusively used for concrete expansion joints, retaining wall construction, etc. Elastomerics are simply additives put in caulks that help them stretch and perform better as a result of their elasticity. Sashco Big Stretch is one that comes to mind. It's a latex caulk that has the elasticity of a silicone. I also don't care for using either 100% silicones that are not paintable or Silicone II that is paintable.

Many sealants also recommend that the bead of caulk be a certain size in order to adhere and perform as advertised. Too often people run a tiny bead of caulk into a crack, wipe 99% of it off and then expect that hairline bead of caulk to hold and never let go from one side or the other in an exterior environment. That's just not going to happen because there is too much expansion and contraction for that teeny-weenie bead of caulk to hold. Looks great for painting, but probably isn't going to last for 20 years. It will probably need to be caulked again the next time you need to paint.

 

Does anyone know why I don't see the quote option any more?

 

Theres a thread over in general chats. It was used a lot by newbies quoting every reply and cluttered up the threads and that just isn't needed. They eliminated it the last update.

You can copy and paste and use the quote button in the menu bar.

It helps to open wordpad or a similar text editor and do the work over there.

 

Well at least know how to determine what not to use - basically anything that's available in a store .

The consensus at this point seems to be that silicone=bad; acrylic=bad unless it's Big Stretch elastomeric; and QUAD is good for sealing the ends of fiber-cement planks. XSleeper, could you be a little more specific about your statement that, "Some of the products you listed I wouldn't use for caulking trim - the Sonneborn NP1, for instance . . . " Which other products would also not be suitable? Even better, what would be suitable if not acrylic and not silicone? Somebody else said Sonneborn should work for basic sealing tasks.

I've just finished putting up T1-11 siding, battens, and trim, including around windows; and installed Hardiplank on the gable end above the same wall. Because it's under a gable end I want to do the best I can. I was going to use GE Silicone II for everything except the Hardie. I'm being advised not to, but I'm not getting much in the way of specifics on what I should use.

How about a vote? In the next week I need to do the following.

What specific brand names would you guys recommend for each item below? "[?]" means I don't have a clue at this point. Basically everything needs to be paintable except sealing under the window cap.

1. [?] Seal the gap between aluminum windows and the T1-11/trim
2. [?] Seal the top corners of the windows
3. [?] Seal the trim around the windows to the T1-11 and to the windows
4. [?] Seal and adhere metal drip caps to the T1-11 over the windows (surface mount is best I could do on the drip caps - they couldn't reasonably be installed under the T1-11). I promise to check it twice a year, but I'd prefer good news when I check them, rather than bad!)
5. [OSI QUAD] Seal ends of Hardieplank to structure
6. [?] Seal other trim like the vertical battens to the plywood
7. [?] Probably a few things I haven't thought of yet
8. [?] Fill some nailholes

Choices are as follows but feel free to add more brand names:

• 4 brands of polyurethane sealant (see list above)
• 4 brands of elastomeric acrylic latex. These are: Big Stretch and the Dap, GE, and Krylon versions that say they are elastomeric
• Acrylic caulk
• Paintable silicone caulk
• Elmer's glue

 

Generally I just use a siliconized acrylic caulk for most prepainting caulking needs. I like the 'white lightning' brand as it holds up well for most interior and exterior work. Polyurethane caulk is great for areas that need a little better 'hold' but can be hard to find in small towns. I don't know if it's available in your area, but the latex caulk sold by Color Wheel Paints [manufactured in Orlando] is some of the best latex caulking I've used.

Often when siliconized acrylic latex caulk doesn't fit the bill, I'll ask the paint rep at the store what would be best. They are always helpful for contractors and I'm sure they would help other customers as well. Architects will usually specify certain caulks on specialty work.

I don't know that I'd overly analyze what you need. There are so many choices when it comes to specialty caulks - it will make your head swim. I painted a new Caterpillar repair center once and the caulking for the exterior wall joints [slab concrete] came in 5 gallon buckets with 1 gal of activator. We burned up 2 drills mixing that stuff and if it dried on your skin - you couldn't peel it off

 

Here's a tip for anyone using Silicone caulk. Even a brand new tube off the shelf of a store like Home Depot (where it turns over quickly) can be bad, in the sense that it will never cure. I found this out the hard way. From my experience you should smell a pungent odor, kind of like Vinegar, from good caulk. If you don't there may be a chance it's OK but I would always test it (regardless of the smell) by laying out a little bead and waiting to see if it cures. You really don't want to remove several feet of the stuff if it won't cure.

 

Thank you for the additional feed back..

Welcome to the forums...

This thread is old... I will close it, so please start a new thread with any other questions..

Thanks...