Before and After Sealants: What 8 Years of Coating Mistakes Taught Me

Full disclosure: I'm the person who signs off on coating and sealant orders. I've been doing this for over eight years, and I've made enough mistakes to fill a small binder. The one I explain to new hires happened in 2021, when I approved a “silicone sealant” spec for an exterior project because the chemical family looked right. A month after application, the coating bubbled and lifted. We spent roughly $2,800 removing it. Actually, $2,800 is what I remember; I might be underselling it once you count the labor and the schedule hit.

The mistake was not just a bad product choice. It was an outdated mental model. I searched for “before and after sealants,” compared photos, and chose a product that looked great in pictures—while missing how that material would interact with the wall system. So this article is the comparison I wish I'd had.

It's not a “silicone is always better” argument. It's a framework for choosing between old-school sealants and modern silicone elastomeric coatings.

The Comparison Framework: Old Sealant vs. Silicone Elastomeric Coating

If you found this page by searching dow-corning, dow corning home care, or dow corning allguard silicone elastomeric coating, you're probably trying to figure out whether a flexible silicone coating is worth the money compared with a traditional sealer or caulk. The answer depends on what “sealant” means on your project.

A traditional sealant is a bead that fills a gap. A silicone elastomeric coating is a film that covers a surface. They are both called sealants in product literature, which makes the comparison confusing. To be fair, the old-school products still have a role. But the industry has evolved, and what was best practice in 2010 is not automatically best practice in 2025.

Dimension 1: Chemical Formula vs. Formulation

People often ask for the corn starch chemical formula because they think knowing a material's formula tells them what it is. Corn starch is commonly written as (C6H10O5)n (Source: PubChem). That's true, but incomplete. Starch is a polymer made of amylose and amylopectin chains, and that formula is just a repeating unit.

The same thing happens with silicone. “Silicone” is not one chemical. It is a family of polymers with a silicon-oxygen backbone, plus additives that control cure, adhesion, flexibility, and color. If you specify “silicone” on a purchase order, you have not actually specified the material.

I'm not a chemist, so I won't pretend to explain every bond. What I can tell you from a sourcing and quality perspective is this: always put a performance standard next to the chemistry. Tensile adhesion, elongation, crack-bridging, and VOC limits tell you more than “silicone” ever will.

The Dow Corning home care portfolio is a good example. It includes consumer tubes of sealant, but it also includes formulated systems like DOWSIL AllGuard for building protection. Same silicone family, completely different formulations. (Note to self: never order by generic family again.)

Dimension 2: Before and After Sealants—What Photos Don't Show

Search “before and after sealants” and you'll see the same visual story: an old, cracked wall and a clean, finished wall. I used to love those photos. Now I ask three questions before trusting one:

1. What was the substrate condition before application?
2. How long after application was the photo taken?
3. What movement does the wall go through during a year?

From the outside, a before-and-after image looks like proof. The reality is that it is just a moment in time. A sealant can look perfect for six months and fail after the first freeze-thaw cycle. I learned this the hard way in 2022, when a project that passed inspection developed cracks at the joints before the one-year check.

Silicone elastomeric coatings, like the Dow Corning AllGuard line, are designed to bridge hairline cracks and move with the substrate. A traditional caulk is not. That's the main difference to look for: a bead will eventually split when the wall moves; a properly selected coating film can stretch. This isn't marketing. It's why the product category exists.

That said, there are places where traditional sealants still win. Isolated control joints and window perimeters are usually better served by a caulk, because you need a thick, squeeze-in-place seal. A coating film alone won't fill a wide gap. The before-and-after story should be “both/and,” not “one kills the other.”

Dimension 3: Application, Cure, and Lifecycle Cost

This is where I have wasted the most money. A low-priced sealer can cost more per square foot over a five-year period if it needs recoating or fails. In 2021, I chose a cheaper option over a silicone elastomeric coating because the initial price was about 40% lower. The failure cost me a repair bill around $3,200 and a schedule delay. Actually, the delay was closer to two weeks once we stripped the coating and let the substrate dry.

It took me about 150 orders to understand that lifecycle cost matters more than unit price. Everyone told me that early in my career. I only truly believed it after paying for a failed application out of my project budget—well, technically it was the company budget, but I was the one who had to explain it to the client.

Silicone elastomeric coatings generally need a clean, sound substrate. Application is not complicated, but it is not “just paint.” Drying and curing depend on temperature and humidity. If you ignore that, you will get cosmetic defects or adhesion problems. (Mental note: always include a cure-time check in the pre-installation meeting.)

What About Dow Corning AllGuard Specifically?

I get a lot of questions about dow corning allguard silicone elastomeric coating. The query usually comes from someone comparing it to ordinary exterior paint. According to the current Dow technical data sheet for DOWSIL AllGuard (available from dow.com), it's a high-solids, breathable silicone elastomeric coating designed for exterior masonry and similar substrates. It's not a caulk. It's applied as a film and provides weather protection, crack-bridging, and water vapor permeability.

I'd rather point you to the current datasheet than quote specific numbers from memory, because product specs can change. The practical takeaway: if you have a wall with hairline cracks and weather exposure, this product category makes sense. If you need to seal a wide gap between two moving components, you need a traditional sealant, not a coating.

Quick Aside: Can Adults Get Sealants on Teeth?

This article gets traffic from home improvement searches, but someone always lands here asking, “can adults get sealants on teeth?” Yes, adults can get dental sealants. Dentists routinely place them on adult molars when there are deep pits, grooves, or a history of decay. It's a preventive treatment, not a cosmetic one. I'm not a dentist, so please talk to yours about whether it's right for you.

Completely different category, I know. But I'd rather answer the question than leave you reading the wrong article.

Which Should You Choose?

Here's a simplified version, with the nuance after it:

• Choose a silicone elastomeric coating when you need whole-surface protection, crack-bridging, and a breathable film.
• Choose a traditional sealant when you need to fill a specific joint or gap, especially at moving edges.

In my experience, the best projects use both. The real question is where the wall changes behavior. Corners, terminations, and transitions often need sealant. The rest of the wall may need a coating.

The fundamentals haven't changed: understand your substrate, prepare it properly, and buy by documented performance. But the execution has evolved.

My rule now is simple. I don't buy by chemical name. I buy by test results and field history. If you take one thing from this article, let it be that.