Sikaflex 227 Vs. Sikaflex 221: What’s the Difference?

The main difference between Sikaflex 227 Vs. Sikaflex 221 is that Sikaflex 227 is optimized for faster curing and bonding in car body applications, while Sikaflex 221 is a more general-purpose adhesive sealant with broader substrate compatibility and a slower cure. Sikaflex 227 also has a lower odor.

Sikaflex 227 Vs. Sikaflex 221: Specs & Uses

⏰Skin Time

Sikaflex 227: 40 minutes

Sikaflex 221: 60 minutes

🆚Application Temperature Range

Sikaflex 227: 5°C – 35°C

Sikaflex 221: 5°C – 40°C

🛠️Common Uses

Sikaflex 227

– Faster skinning and curing speed
– Made for car body sealing
– Low odor

Sikaflex 221

– Slower skinning and curing
– Multi-purpose adhesive sealant
– Bonds well to many substrates

Technical Info

Sikaflex 227Sikaflex 221
Total Score★★★★★★★★★
Chemical base1-component polyurethane1-component polyurethane
Colors AvailableBlack, whiteWhite, grey, black, beige
Cure MechanismMoisture curingMoisture curing
Density (uncured)1.3 kg/L1.3 kg/L
Datasheet📥Sikaflex 227 Datasheet📥Sikaflex 221 Datasheet
Non-sag propertiesGoodGood
Curing SpeedFasterSlower
Shore A Hardness4040
Tensile Strength1.7 MPa1.8 MPa
Elongation at Break600%500%
Tear Propagation Resistance6 N/mm7 N/mm

My Hands-on Test of Sikaflex 227

I have used Sikaflex 227 for various purposes over the years, and it has always worked well for me.

Recently, I needed to remove the old sealant around my home and replace it with new caulking. The builder used Sikaflex 227 when the house was built, so I decided to stick with the same product.

Unfortunately, I couldn’t find it in any local stores, but I found it immediately on Amazon and ordered it right away. The product arrived in a flimsy paper envelope with no other packaging, and the bottom of the tube was damaged in shipping. Nevertheless, I was able to use it successfully with a caulking gun.

I have also used Sikaflex 227 to seal gaps in my driveway and prevent mildew from getting into my living room. In both cases, it did the job perfectly. However, I have noticed that the product has gotten a bit pricey over the years. It’s still the best sealant for metal roofs, but the cost is a bit high compared to other options.

Re-caulk the roof of my Airstream

One thing to note is that the color of the product is black or white, which can stand out visibly on aluminum surfaces. However, it sticks to clean aluminum and seals leaks and holds up for a number of years. It’s also good for crack filling where the slab is not completely level, but it does require tooling to achieve a smooth finish. It’s not suitable for use where a self-leveling finish is required.

If you’re planning to use Sikaflex 227 for pool coping grout repair, be aware that it needs tooling and is not a self-leveling caulk. Also, be sure to wear gloves or plastic throwaways as the product can stain your skin.

Sikaflex 227
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2 reviews

    • While Sikaflex 221 is often used on RV roofs, it may not be suitable for this specific application. It is important to ensure that the material is compatible with the surfaces and substances involved. Additionally, Sikaflex 221 may crack over time due to expansion and contraction, so regular inspection and maintenance are necessary to prevent leaks.

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My Hands-on Test of Sikaflex 221

Sikaflex 221
I’ve used it to attach fenders to a sub-structure in my van and believe that the fender would break before the adhesive fails.

The application process is easy, and it gives a nice look. However, it’s essential to follow the instructions and wear gloves to keep it off your skin since it’s challenging to remove.

I’ve also mounted 2×3’s to the cargo van floor as part of the sub-floor structure, and the adhesive is incredibly strong with good flexibility. I also used it to install a fan on the roof of my van. After laying down three beads around the perimeter of the mounting bracket, the adhesive held everything in place with just tape for clamps. I was able to continue the installation after letting it set for about an hour.

What I love about Sikaflex 221 is that it’s safe to use with drinkable water storage, making it ideal for sealing various direct-contact-with-weather areas along with a potable water tank. It’s flexible, so it won’t crack, and it doesn’t peel. However, cutting it with a blade requires some effort.


It is easy to use, but it can stain, so it’s important to wear the proper protection, including gloves. Although I couldn’t find it at HD and Lowes, I finally found it here, and I would assume it’s a decent price, but I just don’t have anything to compare it to. I would definitely buy it again and have it.

Sikaflex 221 adhesive worked great when I had to secure a stainless steel panel on my Prevost bus, which was separating from the storage door. I have also used it to attach the chrome to the rear window, and it worked better than I expected.

I also used Sikaflex 221 to seal some fittings on my boat, and it has excellent adhesion, and it’s paintable. I have been using 3M 5200, but I like this sealant better, and it keeps the water out of my sailboat.

In addition, I had to put a shelf into a fiberglass headliner, and I bonded 2×3 boards directly to the fiberglass, then screwed the shelf into those boards. The shelf hangs from those boards, and that was four years ago. Nothing has moved at all, even while bouncing up and down on some rough roads with the shelf fully loaded. It’s still as solid as the day I put it up.


💬 FAQ of Sikaflex 221

Q: Can Sikaflex be used to bond a window into an aluminum U-channel on an RV? Is it removable if needed?

A: Yes, Sikaflex 221 is suitable for sealing RV windshields to aluminum and fiberglass with fiberglass adhesives. It is easy to remove before it cures but extremely difficult to remove once it has fully cured. Another option is Sikaflex 291 Vs. Sikaflex 292i.

Q: Has the inventory issue with Sikaflex been fixed? I ordered two black tubes but received two white ones.

A: While I have always received the correct color when ordering Sikaflex 221 through Amazon, it is best to contact the seller directly to confirm the availability of specific colors. If the product received is not what was ordered, it is best to request a refund.

Q: Is Sikaflex suitable for filling in concrete floor cracks? Will it self-level?

A: While Sikaflex 221 may hold up on the concrete, it is not designed to self-level. It is important to select the appropriate sealant for the specific application.

Q: Is Sikaflex the best sealant to use on windows in a manufactured home?

A: Sikaflex 221 has been successfully used to seal windows in Elite Motorhomes, and my father-in-law has never experienced any leaks or product failures. However, it is important to ensure that the material is compatible with the surfaces and substances involved.

Q: Will Sikaflex adhere to a surface cleaned with isopropyl alcohol that has residual spots of previous silicone caulk?

A: While Sikaflex 221 is very sticky and may bond to the surface, it is important to thoroughly clean the surface and remove any residual caulk before application. Masking is also recommended to avoid unwanted cleanup from other surfaces.

Q: Can Sikaflex be used to glue and seal vinyl shower walls?

A: Yes, Sikaflex 221 can be used for this application. It is important to ensure that it is marine grade and compatible with the specific surfaces involved. Testing on a small scrap piece is recommended before full application.

Q: Will Sikaflex bond a rubber stair nose to a rubber coin mat?

A: Yes, Sikaflex 221 is suitable for bonding a wide variety of substrates, including rubber. It is designed to create permanent elastic seals with high adhesive strength.

Q: Can Sikaflex be used to seal seams in rubber gym flooring?

A: While Sikaflex 221 may work for this application, the grey Sikaflex sealant may be a better option as it is designed to be more flexible. The black Sikaflex adhesive may settle flatter.

Q: Can mineral spirits be used to prep the surface before applying Sikaflex?

A: While some solvents may be used to prep surfaces before application, it is important to follow the instructions and recommendations provided by Sikaflex to ensure proper adhesion. Additionally, appropriate safety measures should be taken when working with solvents.

Sikaflex 227 Vs. Sikaflex 221