Should You Caulk Wood Siding? [And How To]

A wood siding is an eco-friendly option in naturally insulating and protecting the structure. Possibly, you just installed one on your house and are sitting here wondering what to do with all the gaps between the panels. Let us find out whether the traditional method of caulking is of any help here.

Yes, you may caulk wood siding. However, many manufacturers will tell you against it. Wood is a porous surface that changes structure depending upon the environmental conditions around it. Caulking may damage the wood surface by prohibiting expansion if not done correctly. Standard wood siding caulking should involve the following steps:

  • Choosing the right caulk and gun
  • Applying primer before caulking
  • Using a backer rod 
  • Using the gun at a right angle
  • Smoothening the bead of caulk

Wood siding sure is a vulnerable choice. It only makes sense that the steps you take to protect it are equally considerate. Keep reading to get insight into how exactly caulking for wood siding works.

Gray wooden siding of a ranch style house with white painted window frames, Should You Caulk Wood Siding? [And How To]

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Why Is Caulking Wood Siding Not Necessary?

Deviations in temperature, weather, and precipitation cause the surface of the wood to expand and contract. Since the material is subject to constant fluctuations in structure, it can not sustain caulking in many instances. A caulk layer directly rests on the surface to close gaps. So, it may hinder the natural movement of wood. This hindrance could lead to damaging the wooden panels. 

However, that does not mean it eliminates all scope for caulking and its many benefits. With the proper technique, one can apply a caulking layer so precisely that it survives the test of time. Here, the key is to use a good primer. The primer sets the base for the caulking through which direct exposure to the wood is limited. We discuss this procedure further in the article.

Benefits of Caulking Wood Siding

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A couple caulking the wooden siding of their house

The need for caulking is not limited to aesthetic benefits alone. Any unsightly holes and cracks in your siding structure may allow moisture, air, and unwanted bacteria to pass in. By triggering such penetrations, the gaps nullify the purpose of the wood siding. 

If installed correctly, the benefits of caulking include, but are not limited to:

  • Preventing temperature regulations by blocking wind, snow, or rain outside 
  • Preventing water leakage and accumulation of excess moisture 
  • Keeping insects from intruding into the house 
  • Amplifying the cosmetic appearance 
  • Eliminating conditions for mold and mildew to occur

What Happens If Water Gets Behind Siding?

It is easy for rainwater or any leaking water to slide behind your wood siding and heavily damage it before you can even notice. The effects will begin as stains and lead all the way to rot the wall. This rotting will promote growth for mold and deeply challenge the integrity of the structure. 

Where Should You Not Caulk Siding?

Never ignore the question of what places should ideally be left uncaulked when deciding on the siding. If you do so, you would be surprised at the damage an incorrectly placed caulk may pose. 

The Trim

Trim is the protective cladding for your doors and windows on the exterior. Traditionally, it goes atop the siding, resulting in a small cavity. You will have to avoid caulking this gap as it will inhibit the air circulation and damage the drainage system. This damage is because the gap doubles as a water outlet in the case of leakage. So, it is best if you avoid preventing it from functioning as it should. 

Bottom of Horizontal Siding

Horizontal siding often extends cover to another sheet below them. Should you ever caulk the bottom of such a structure, you will hinder the water exit. Additionally, this may dampen the environment allowing for mold and mildew to grow. 

Tongue-and-Groove Siding

Tongue-and-groove siding is a type where one end of the board slides into the groove in a second board. If you are using this type, do not caulk it together. 

Siding Nails

Always avoid caulking atop siding nails, especially when it is wood siding. When the time comes, wood will contract and expand. This contraction and expansion make them an unstable fixture to rely on. 


Flashings operate as outlets in the case of water penetration. Thus, caulking them would eliminate the exit and cause moisture to dampen the structure. Additionally, flashings are waterproof structures. So, caulking them does no extra good at all.

Where Should You Caulk Siding?

Ideally, you should caulk all parts of the structure that accommodate hazardous gaps and cracks. These openings may soon allow for penetration, leakage, and overall structural damage. 

However, there are a few particular places moisture loves to hide. Ensure that you caulk them properly. 

  • Corners and edges of the house 
  • Cracks or holes in the structure
  • Meeting point of two sidings 
  • Gaps around baseboards 
  • Around the trim and butt-joints 
  • Meeting point of windows and doors

Should You Seal The Bottom Of Siding?

Be it a horizontal structure or vertical, do not caulk the bottom of the siding. It always acts as a channel for draining water out. Caulking it would lead to moisture accumulation, thus resulting in a humid environment. 

How Do You Caulk Wood Siding?

Fortunately, caulking wood siding may not be as hard as one would assume. With the correct instruments available, here is a DIY guide for caulking. 

Choosing The Right Caulk

Remember that wood is an atypical case concerning caulking techniques. Likely, the traditional materials that work best for most do not work for wood siding.

What Is The Best Caulk For Exterior Wood Siding?

Silicone caulk is suggested for wood siding by the Department of Energy. While it comes with the extra need for frequent maintenance, it ticks the precise binding nature wood siding requires. However, if you are faithful to silicone caulking, you can instead use a hybrid caulk. 

Choosing The Right Gun

A caulking gun on a white background

The caulking gun is going to be the workhorse of your procedure. If you don’t get that bead of caulk precise and smooth, it may nullify all efforts you make. The scope of this project is short-term so, you may not invest in a fancy caulking gun. 

However, you do need to ensure the rod is in working order, there is a healthy thrust ratio, and it is easy to maneuver. A simple caulking gun does the deed right, with one drawback only. It retains pressure even after you stop pushing, thus taking away control over the application. 

Many have suggested a dripless gun in this regard. A dripless gun pulls the plunger back when you release the trigger, giving a more clean and precise result.

Getting The Tools

As long as you have the gun and caulk at-ready, there are only a few basic materials you’ll have to make arrangements for. Here is a list of what you will need to caulk your wood siding: 

  • Exterior caulk 
  • Caulking gun
  • Utility knife or sharp blade
  • Garden hose or compressed air can 
  • A foaming brush 
  • Old rag 

Cleaning The Workspace

Ensure that the workspace does not have oil, debris, paint, or previous caulking layers. You don’t want to waste your caulking bead as it won’t stick on a coated surface. Grab a garden/water hose, and thoroughly rinse the area. You may even opt for a compressed air can for this purpose. Afterward, you will have to wait for it to dry up to proceed further. 

Preparing The Gun

Grab a utility knife or any sharp blade to cut through the nozzle tip. Many caulking guns come with pre-installed spout cutters, which are handy but not thoroughly beneficial. 

Cutting the nozzle must be very precise as it will define the course of your entire procedure. Should you cut at the wrong angle, you will end up with a frizzy sealant bead. 

Experts suggest many different angles for this step but, we advise you to go for the classic 90°. Since you are already holding the gun at a certain angle, it makes sense to give an even outlet to the bead. This “square cut” further eliminates the need for smoothening tools and gives you a linear caulk bead directly. 

Another step at this stage is to perforate the seal opening with a needle. This way, it will allow the caulk to emerge uniformly out of the nozzle. 

Priming The Surface

Since you are dealing with wood siding, all life depends upon getting the surface rightly primed. Acrylic latex primers are infamous for their flexibility and adhesion to the wood surface. Apply a coat of primer all over, but pay special attention to getting it into the intersections.

Getting The Right Caulk Bead

  • Aim the end of the nozzle at the top of the intersection.
  • Keep the back end of the gun upward to slide down smoothly.
  • Apply gentle pressure on the trigger and gradually ease it as you glide downward.
  • Readjust the caulk gun at each intersection. 
  • Don’t worry about any glitches that may have occurred at this stage. Reapplying the caulk would only damage the whole bead.

Straightening The Curve

If used steadily, a square cut nozzle will take care of all the smoothening requirements itself. However, the bead may diverge during application. Make sure you do not either use your finger to smoothen it or some worn-out tool. 

You must be careful not to let human oils or dirt intrude into the composition of the caulk. Use a foaming brush and gently dab on the bead to straighten out any incurving. 

Finishing Touches

Grab an old rag and wet it with water. Before the caulk dries up, wipe off any excess that may have ended up outside the gaps. If you need visual help on how to apply caulk, here is a YouTube video demonstrating the steps to do so correctly: 

Bonus Steps

Your caulking is perfectly well-installed if you followed the instructions correctly. You can always take it a step further by applying any of the following steps.

  • Before application, use a painter’s tape to define the area of exposure. This method results in a more refined caulk bead. 
  • For aesthetic purposes, you can paint the siding after the caulk has dried up. The painting hides the sealant and makes up for any cosmetic errors.
  • Before application, you can install a backer rod in the gap. For deep cracks and porous surfaces, a backer rod helps anchor the caulking. They allow it to remain durable and give off extra insulation.

If you need a visual guide, here is a YouTube video demonstrating a backer rod:

How Do You Close The Gap Between Siding And Foundation?

Caulking is the standard answer for sealing all gaps in siding structures. Many people have reported the positive effects of silicone caulking to close up the gaps between siding and foundations. Interestingly, users have also used rolls of bristle brushes to do the deed. 

Final Takeaway

We have given you a detailed sketch of every aspect you must consider before caulking your wood siding. Good luck with following the steps to make your home a safe area!

Before you go, do you have other concerns about wood siding? Have you noticed them bulging out? We have some answers. For more information, check out our post here.

Have you noticed mildew growth on your wood siding? We can also offer some help in that area. For more information, check out our post here. Until next time!

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