RV Window Seals Shrinking? Do these things now!

Everything you need to know about shrinking rv window seals

rv window shrink

You never really believe that your RV window seal will shrink. And if it does, you expect the shrinking will be very minimal and won't make much difference in how effectively the window insulates. Both of those assumptions are wrong.

The fact is: RV window seals do shrink over time (and some types more than others). Initial shrinkage can cause an unsealed gap of up to 1/ 8 inch all along a framed window; after 12 to 18 months, additional shrinking can open gaps as wide as 3/ 16 inch! That's enough space for cold air to seep inside when temperatures drop below freezing. Not only does this waste expensive propane, but the resulting drafts make temperatures inside every bit as uncomfortable as they would be if the RV were not insulated at all.

In extreme cases, these tiny gaps also can allow moisture to seep in, resulting in rotting window frames and seals, and eventually structural damage to your motorhome or travel trailer.

The culprits are sun exposure and temperature changes. When they combine, small hardwood fibers that adhere the rubberized sealant material readily shrink away from the metal frame of an RV window. This is called outgassing . It's a natural process caused by exposure to heat as the sun bakes down on an uncovered surface; it might be likened to what happens when you bake cookies for too long – many don't come out looking like their picture-perfect selves.

But how do we solve this issue?

To solve this issue, follow the methods below.

  1. Method 1: Stretch out the Seal
  2. Shrinking occurs on seals overtime. This is due to the seal being compressed down onto the frame and then getting colder at night exposing it to shrinking. The quick fix is to get out a garden hose and turn the water on full blast, then run along your window seal and use your hand/arms to stretch it out. Make sure you have a squeegee by you as the water will cause the sealant to become slippery.

    Another way to stretch out the seal is to:

    • Remove the seal that has been shrinking from your window
    • Use 303 Protect Spray on the said seal
    • Use your fingers to massage the 303 Protect Spray into the seal you just removed.
    • While you massage it, stretch it.
    • Afterwards, clean away any remaining dirt and debris on your rubber window seal. Try not to forget this step otherwise dirt may get stuck on your seal after fixing a shrinking RV window seal.
    • You can now put the seal back around the window.
  3. Method 2: Replace Your Seal
  4. This method is very easy but I would recommend first trying method 1 above just in case it works. If not, continue reading:

    • First remove your screen from the window if there is one installed already (anyone who has tried doing this before knows it can be very challenging).
    • Remove the seal from around your window by prying on it with a thin object (a toothpick works great). Now clean all of that old seal off of your window. Make sure you get it nice and clean or else the new seal won't stick right.
    • Now apply 303 Protect Spray to where you are going to put the new seal, make sure you massage it in as well.
    • Now place your new seal around your window making sure that its even and there are no gaps in between the glass and the rubber. This step is key because if these two things aren't done right, water will eventually seep into your RV causing lots of damage.
    • And lastly replace any screen parts you disassembled.
  5. Method 3: Use heat on your seal
  6. Use a heat gun and use it on your window seal. Make sure that you are careful not to burn your rubber seal! DO NOT USE A FLAME TO HEAT YOUR WINDOW SEAL, IT MAY CAUSE FIRE DAMAGE! Just place the heat gun along the section where you want more flexibility and controllability. You may also try using a hair dryer but make sure that it is on low setting so as not to melt anything.

  7. Method 4: Rv window seal tape
  8. This can be used to fix the shrinking rv window seal in a fashion but if it is not done right the seal will still shrink or still leak. We suggest you use this method on small cracks that are located in the corners of your windows instead of using it on a long crack.

    Start by measuring the width of the crack so you know how much tape to purchase for your RV windows. The tape should not be wider than one inch and then cut into small strips about an inch wide to fit inside each corner around the window seal.

    The next step is to remove the old caulk from around the window seal where you need to apply the tape. To do this, start by pulling up any stickers and labels that might have been put there recently; they will get in the way of applying new caulk. You may find some old caulk that has hardened; in this case, you should scrape it away with a putty knife and use a wet rag to wipe up any residue.

    You can apply thermal window insulation around the entire edge where the seal is located on both sides of the window. Before you do this, be sure that your RV windows are clean and dry inside because dust or moisture can interfere with how well the tape sticks to the glass. Once everything is clean and dry, cut out small pieces of cloth fiberglass with scissors similar to what we have shown here above.

Rv Window Seal Replacement and Repair

Dicor Corporation Standard Seal-Tite Reseal Kit

Dicor Corporation Standard Seal-Tite Reseal Kit

Sealing the openings around RV windows doesn’t have to be difficult or a time-consuming task. With this RV window seal kit, you can seal out rain and drafts from your RV’s windows. The kit includes all the parts that you need to repair 6 – 8 windows, depending on size. By sealing these windows well, your trip will become more comfortable and enjoyable. No matter where the road takes you, this seal kit is an affordable way to ensure your RV is protected from a leaky or drafty window.

XFasten Black Butyl Seal Tape

butyl tape for rv

If you're looking for a reliable way to seal leaks, RV butyl tape is the perfect solution. This strong tape is designed to create a watertight seal, making it the perfect choice for sealing cracks and seams on your RV.

Geocel 28100V Pro Flex Crystal Clear RV Flexible Sealant

clear rv sealant

Clear RV Sealant is a clear, flexible sealer that seals leaks in all RVs. It’s strong enough to seal some of the largest leaks. Clear RV Sealant can be used on virtually any surface including fiberglass, metal and wood. No matter where the leak is located, Clear RV Sealant will seal it fast.

How do you Prevent RV Window Seals From Shrinking?

  • To prevent window seals from shrinking, you could first hire a professional to do the job for you. However, if you are the one who will be doing the job, it is best that you follow these steps:
  • Do not leave your rv in extreme weather like: Ambient temperatures below thirty degrees ( 30 ) or above one hundred 20 degrees ( 120 ) as this will cause the rubber to crack and shorten its life.
  • Clean & Inspect it before each season - this is very important because rubber deteriorates faster when in contact with the elements.
  • Make sure you identify how many cracks there are in each window, if they are deeper than a 1/8" deep then have them replaced because if you just fill those cracks with caulk they will split open later on due to expansion & contraction from temperature changes.
  • Type of window seal

    If you own an aging RV that has rubber/neoprene window seal(s), then sooner or later you'll notice a few cracks especially around the corners of your windows. This is normal for those window seals because they expand and contract with changing temperatures which in turn causes those cracks to form due to stress. However, this problem can be fixed by sealing up all the openings located between your rv wall and floor, trailer bed walls and floors as well as some other places such as around and underneath your shower, bathroom and kitchen window seals.

    Things that will destroy your RV Window Seals

    Using high-pressure water hoses or simply letting the rain beat down on them, as well as using a dirty wash rag which are full of chemicals like dish soap and all solvents which will act against the silicone you applied.

    You must dry off any excess water right away and do not use anything like pressure washers close to your window seal.

    What Happens When Your Window Loses Its Seal?

    The worst thing that will happen is your window will pop out of its frame if it is not sealed properly, because that lets all the air in and makes your seal shrink.

    A shrinking RV window seal is never a good thing unless you want water seeping in. Water that seeps in will be able to damage the wood on your window as well as the walls.

    If you have a wooden frame around your RV windows, then this will allow water to seep into that wood and rot it out of existence.

    This can be dangerous because if there is enough water pressure behind it; it will pop the window right out of its frame or crack the glass. So keep an eye on your seals and make sure they are always in good working order so that this does not happen to you.

    Will you have to replace windows with broken seals?

    No, you do not have to replace all of your windows if one or two have bad seals. Some people say you should replace the frame along with the seal because when they go they usually take some of that frame with them.

    All you need to do to have a perfectly working window is to repair the seal. This is not very expensive and the job can be done in an afternoon.

    When you take your windows out to repair them, do not throw them away just yet. Make sure that when you put the old window back into its frame, it fits like a glove. If it does not fit right, try another one until you find one that fits perfectly.

    If none of your windows fit then maybe this is a time to consider getting new ones; especially if your RV is older and made with cheaper materials. You never know what kind of problems these windows will give you in the future and spending a little extra now may save you money on repairs down the road.

    Repair cost for rv window seal

    Repairing a shrinking rv window seal can vary in cost. It usually depends on if you get new windows, how many windows need to be replaced and where you live. The average cost of repairing your RV window seal is around $100. Although this may seem like a lot at first it will help prevent major problems in the future. After all, most people do not want their rv holding water inside while traveling down the road. A leaking rv window seal can cause major damage to your coach.


    You have just learned all you need to know about preventing rv window seals from shrinking. RV window sealing is a necessary and sometimes tricky process. With the information that we have provided here, we hope that you will never run into a problem with it again. If you do get shrinking window seals, bookmark this blog post so you can refer to it at a later date.

    With this article, we are concluding our series of articles about "RV Sealing Tips". We hope that all the information was helpful and you have learned to prevent any problems during sealing your RV windows and doors from now on.

    Should there be anything else we can help with, please feel free to contact us anytime using the comment box on our contact page! Do not hesitate to ask if you think we missed something crucial in this article or if you would like us to write more tutorials or shorter blog posts in the future. We work continuously to provide high quality content for our readers. Thank you for taking time out of your busy day to read through this post.

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    About Author:

    image of Kevin Pommells

    Hi, I'm Kevin Pommells, a lover of camping and the great outdoors as everyone says nowadays. I'm also a passionate soccer fan and the proud owner of CamperRules.com, a website dedicated to helping campers and outdoor enthusiasts make the most of their adventures. With years of experience exploring the wilderness and a deep love for the sport of soccer, I'm always looking for new ways to combine my two passions and share my knowledge with others. Follow me for tips, tricks, and insights on all things camping and outdoor recreation.

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