Best Sealant for Polycarbonate Skylights

Updated 10/28/2025 | Published 03/10/2025

Products Featured in This Question

Alpha Systems AlphaThane 5121 Self-Leveling Sealant for RVs - White - 9.8 oz - Qty 1

(30)

$19.94

Specialty Recreation Skylight Sealant - 10 oz

(32)

$27.53

Question:

Is the alphathane 5121 compatible with polycarbonate skylights ?

asked by: Mike C

Expert Reply:

Hey Mike, thanks for reaching out!

The Alpha Systems AlphaThane 5121 Self-Leveling Sealant # AL35KV is designed for wood, metal, and glass materials. Since your skylights are polycarbonate I recommend using the Specialty Recreation Skylight Sealant # SR86RR instead because it is designed for polycarbonate skylights.

How many skylights are you needing to seal up?

expert reply by: Jon G

Jon G.

10/27/2025

Hey Mike, how did things go with the Specialty Recreation skylight sealant on your polycarbonate skylights? Your update could make it easier for the next person sealing similar skylights.

Mike C.

10/27/2025

@JonG oops sorry on last reply it showed up weird on my phone. I took it to a RV repair facility and had it fixed, I ran out of time. the people at Forest River told me i should use the alpha thane stuff which i knew had to be wrong since it didn't stick to the first sky light. Pretty Sad your year old travel trailer needs skylights replaced due to poor workmanship. Thanks for confirming, i have three tubes of the stuff you suggested that i will use for other reseal jobs in the future.

Jon G.

10/28/2025

@MikeC Glad to hear you were able to get it all working with the sealant we talked about! That is really frustrating though that your skylights started to act up after only a year.