Friday, May 26, 2023


Take care of those insert moldings. Here are the products to use

This is a real unit, with a real problem, and it’s in our real shop. This series was created in hopes of helping you better understand your unit and how to best maintain it. This episode shows you the danger of not keeping an eye on your RV insert moldings. In my experience, one of the most missed items is the insert molding screw cover. This protective plastic covers the screws at the roof line edges as well as the vertical and horizontal side seams of all RVs.

Unless you visually inspect under the insert moldings, you will not see potential water damage until it’s too late. Insert moldings help to keep the moisture, condensation, rain, dirt, and other elements out of your RV. By sealing the edges of the aluminum molding it protects the screws along the roof, body, front, and rear seams.

This is important and, from my experience, often a missed step when weatherproofing and protecting your unit. When water gets past this plastic insert molding screw cover, it can cause serious damage. Water spreads through the unit and invites the growth of mold, rusts screws and causes dry rot in walls, roof joints and floors as the water travels down the aluminum framework in the wall.

I recommend that you replace the insert molding as needed every 2-3 years.

Insert molding screw covers shrink in both directions and will allow water to get in. This shrinkage is caused by age, sun, soaps and elements. The tattletale sign is tapping it and seeing if it makes noise within the track. I hope this tip helps protect your investment.

DIY products to use

Dicor Non-Sag Sealant — You will want to use non-sag sealant on all corners and side seams on the roof. Non-Sag Sealant is offered in several colors:

Dicor Self-Leveling Sealant – Roof surface, for moldings, seams, vents, skylights, etc.

More from Dustin

Read more of Dustin’s articles here.


Dustin Simpson
Dustin Simpson
I have worn many hats in the RV industry through the years. From an RV Technician, Warranty Administrator, Parts Administrator, Parts Manager, Service Manager and now Business Owner. I have even been deemed an RV Expert by the California court system, working on behalf of the customers, dealers, and manufacturers. My repair facility has been servicing customers at the same location since 2003. What sets us apart from the dealerships is we are here to fix and maintain what you have, and not sell you a new one. Whether you own a million-dollar unit or an entry level, my message to you will be the same, it needs to be maintained.


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Neal Davis
1 month ago

Thank you, Dustin!

Jim Keltner
1 month ago

Dustin, we had a broken part on our roof that allowed water in during 2 of the “atmospheric rivers” recently. I have changed out the part (plastic cover above the refrigerator) and thought that was fixed (the floor is a disaster still needing work). Now I see the refrigerator starting to settle! We are currently in Port Townsend WA volunteering with HfH but will be home to Walnut Creek in mid May. What is the best way to contact you so you can take a look at what I need and the cost? We have a 99 36′ Fleetwood Discovery.

Dustin Leigh Simpson
1 month ago
Reply to  Jim Keltner

jim, give us a call at the shop to schedule an inspection. 209-263-7040

1 month ago

“This protective plastic covers the screws at the roof line edges as well as the vertical and horizontal side seams of all RVs.”

Many, perhaps, but not all RVs have the screw strips with the “pop in” plastic molding material. Towables tend to have it more than motorhomes.

I have owned three DP motorhomes…two Winnebago and my current Newmar… and none had this. I would say most better built class A’s don’t have it. Not sure it is used on class B’s at all.

Dustin Leigh Simpson
1 month ago
Reply to  Spike

Thanks for sharing.

1 month ago

Just purchased a roll of molding. One front side on my TT started cracking at the bottom last fall after 4 years.. I even wipe mine down with 303 every time I wash it to try and stop the UV damage.Of course the manufacturer used the cheapest molding they could find. Hardest part of the job will be removing the old sealant at the top..

Dustin Leigh Simpson
1 month ago
Reply to  Bob

Thanks for sharing and I also recommend applying 303 on everything.

1 month ago

Poor design to begin with but replacing the screws with rubber gasket roofing screws will stop the water seeping in. Also I never use silicone on anything. Nothing sticks to silicone, silicone sticks to nothing. Much better sealants are available.

Dustin Leigh Simpson
1 month ago
Reply to  Charley

The term silicone is always used, when using sealant products you need to look for the correct product and application for the type of silicone your applying.

Wayne Harris
1 month ago

There isn’t anything in the video regarding the point of the video which was to tell me how to keep this from happening.

Bob P
1 month ago
Reply to  Wayne Harris

Don’t take it out in the sun, UV rays destroy everything they touch including skin.

Dustin Leigh Simpson
1 month ago
Reply to  Wayne Harris

Regular inspection, recommend replacement as needed typically every 2-3 years. Think of it like a manicure, when it’s needed do it. It also depends on your use, weather conditions, soaps and cleaner you use, how it’s stored and products you apply to protect it.

You can apply 303 to help protect the insert moldings from shrinking up.

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