Why is Silicone Caulk Bad For Wood?

By Scott Sidler • June 24, 2019

why is silicone caulk bad for woodI get a lot of comments from people wondering why I don’t use silicone caulk on things like leaky wood windows or doors. Silicone seems to be the savior of the caulk aficionado. The creme de la creme of the caulk kingdom with nary a competitor to be found who can challenge its amazing performance. Don’t get me wrong I like silicone, but like everything it has its time and place and used outside of that it creates more problems than it solves.

In this post I’ll lay out my case and all you silicone advocates can argue with me in the comments below. I doubt you’ll change my mind because my opinion is based on years of experience trying to dig the stuff out of old houses in places it never should have been, but you’re welcome to try.

Silicone + Wood = Bad News

When used on bare wood silicone can be deadly and destructive. It grabs on tenaciously, which you might think is a good thing, right? After all the you want your caulk to have great adhesion and flexibility so it will seal things up for a long time. Well, just like everything silicone caulk has a lifespan. According to United Silicones, silicone has a minimum life expectancy of about 20 years which is a good long time.

So what happens at the end of that 20 years? Well, you have to dig out the silicone and replace it with either more silicone or some other sealant. If you have ever tried to dig out silicone from wood you’ll quickly discover that even on old silicone this is a monumental task that yields terrible results. Removing all the silicone is difficult to accomplish as there is almost always some residue and when you remove it from wood it inevitably grips onto the wood fibers and pulls them with it resulting in a mutilated work piece that requires lots of repair.

When it comes to things like old windows traditional glazing putty is a much better choice. It has a similar lifespan of 20-30 years and at the end of that time it can be removed without damaging the wood. It responds to steam (see the video below) or heat to facilitate removal unlike silicone, and even if some of it remains it is compatible with the new putty or paint during reinstallation. That brings up another point about silicone.

Silicone is Not Paintable

I think most of you probably already know this about silicone that it is not paintable. No how, no way. Paint simply beads up and falls off pure silicone caulk. Since the typical house is painted every 10 years that means you’re gonna have to figure out something to do with the areas that have silicone. Color change? Not for you if you’ve got silicone caulk on your house.

That little point I mentioned earlier about there always being some residue after removal of silicone once again wreaks havoc here. You will have sloppy paint lines wherever the silicone was unless you remove every trace of it which is near impossible without replacing the wood member.

Where Does Silicone Belong?

silicone damage to wood
Damaged window muntin from silicone caulk

It may be easier to say where silicone DOESN’T belong than where it does so let’s go that route. Silicone caulk is excellent at water sealing and flexibility so it has its place in construction. There are two main places it never should be installed, wood or any painted surface. If paint will ever be applied to an area, then silicone does not belong there, ever, in any way. If you have a wood element (painted or not) in your house silicone should never be applied there either.

Most any other application is usually fine for silicone caulk though I use it sparingly. I’m a fan of siliconized acrylic caulks, or their more serious cousin, urethane caulks, because they are more easily reversible and they are almost always paintable.

Please do the next guy or girl a favor and don’t use silicone caulk as a cure all for leaks. It was never designed for that and it usually causes more trouble long term than the short term benefits. Think first and caulk second. Please silicone safely! 😉

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20 thoughts on “Why is Silicone Caulk Bad For Wood?”

  1. We have a home from the 1930’s with many gaps in exterior (portland-type) stucco between wood and cracks within the stucco. These two conditions make up about 80% of our needed stop-gaps. The remaining conditions are gaps between stucco and metal pipes or roofing materials. What are your thoughts?

    We have already taken to heart the suggestion to repair wood windows with glazing putty. Thank you for saving a really nice door from our handiwork.

  2. Something else worth mentioning – silicone caulks and sealants generally require a cleaner substrate than other types (urethane, polyurethane, etc.) to reach their published performance. Product warranties for high-quality gun-grade silicones are usually 15-20 years, but that’s assuming an ideal installation with clean, dry, sound substrates.

    Commercial silicone sealants have their place, as well – but often require primers for certain substrates. The payoff is in superior UV resistance and sustained elastomeric performance (i.e. they stay stretchier longer). So for exposed joints in masonry, windows, etc. in new construction, silicones are often preferred for their performance, and most commercial sealant manufacturers (in Houston, TX I see a lot of Dowsil 790/795 or Tremco Spectrem 1) will have broad color selections; some will blend custom colors as well.

  3. I’ll opt for Lexel over silicone any day. Most other caulks will stick to it so when time comes to recaulk you don’t have to remove every tiniest bit. And if after caulking you discover a small skip or a low point, you can go over it again after it dries. Unlike silicone, it’s paintable, and can be used in below freezing temperatures. Unlike silicone, the clear doesn’t yellow. (It also comes in white). It adheres indefinitely, and does great used in showers or tubs. Only downside is that in many areas it’s hard to find in brick and mortar stores, especially the white.

  4. The last owner of our house (built in 1854) had a son who was a contractor that used silicon caulk on everthing. Every widow pane on the inside of the house has a bead of clear silicon (100% clear) ariund it where it meets the mullion. Since we are slowly rehabbing each window per your handy book this is bit that big if a deal since the windows are due for a complete overhaul. However where it is bad is when he used the same silicon to caulk around the window casing where it meets the wall. In order to remove this caulk (to paint the edge of the casing) we have to dig a hole in the plaster wall and then repaired the gouge with new plaster. It’s very time consuming and because of this I have come to and hate 100% silicone caulk and use it sparingly.

      1. All of the windows in our 1895 Queen Ann were sealed with silicone. After several attempts with different solvents, I tried “De-Solv-It Contractors’ Solvent” and it worked.
        If you spray it on and let sit for 5-8 minutes, the silicone will soften and is easier to remove. The method that works best for me is to use a putty knife and tap gently downwards. The silicone will ease out and then use pliers to pull it free. Use a small tapping hammer and hold it close to the top as to avoid hitting the glass. It is Important not to pry too hard or the wood will get damaged.

  5. I couldn’t agree more! I found silicone caulk on some of the windows I restored and removing it took an exponentially longer amount of time than putty. I also lost a couple pieces of original glass because of it 🙁

  6. Just an FYI, our GC used silicone caulk on the floor, around the molding and every other place they could think of. I think they were addicted to the stuff

  7. Agree with everything said here. I’d like to add one more place silicone is a big no-no and almost everybody uses it unknowingly. That is in furniture polish. Things like Pledge, Liquid Gold, etc. have silicone in them to make the shine and slippery surface that every body likes after they get done dusting. The vast majority of these kinds of products have silicone in them. The problem arises when you decide to have grandma’s bed room set repaired and refinished. Silicone creates havoc with high end finishes. Makes the finish look like the surface of the moon resulting in more work for the refinisher and consequently (at least in my case) more cost for the owner. For everyday (or week, or month) dusting use Endust. For general cleaning use warm water with a few drops of Dawn. Ring out the rag so it’s only moist and dry after.

    Al Fortunato Furnituremaker
    https://www.facebook.com/alfortunatomastercraftsman/
    http://www.alfortunat0.com

      1. Not the automotive ones, but wood finish manufacturer makes ones for their finishes. Problem with wood is that the silicone gets absorbed into the wood and is impossible to get rid of. (I’ve even run it through a thickness planner and it’s still there.) The fish eye eliminators are added to the finish and reduces surface tension of the finish itself and helps level out the finish. If the customer has been obsessive with using the pledge types of polishes, it’s almost impossible to get rid of, other than put it on, sand, spray, sand, spray, and on and on until the fish eye is gone. Time and material = $$$.

  8. Yikes! What would you use then for gaps between baseboard? We have 6″ baseboards and when adding a bathroom we reinstalled the baseboards. Our gc used caulk to fill in between the quarter round top and flat area. Luckily, the color is off white paint, but the baseboards aren’t finished and there are still gaps. This is what happens when there are no historical restorers in your area, I guess. We have a recommended on your list window guy but that’s it. And it’s frustrating!

    1. One trick the old timers used was to make the back of the quarter round angled just slightly so that it would be tight to the baseboard and the floor. Regular quarter round can be altered with a tablesaw in the same manner.

  9. Silicone will leave a residue that prevent future caulks or putties from adhering to the same substrate. This residue will even inhibit more silicone from adhering. Thus the old argument, ” is silicone the best caulk for use around shower and tile bath enclosures?” Probably not.

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