How to stop a crack in wood from spreading and how to prevent cracking

We all know wood tends to crack over time because of moisture and aging. But it does not mean that you have to throw away the whole furniture piece – you can fix those cracks quite easily.

There are multiple methods of stopping cracks in wood and protecting it from more damage. Follow this article to know how to stop a crack in wood from spreading!

How to stop a crack in wood from spreading?

The most simple and effective way is to fix the crack with a wood filler or wood putty.

There are various types of commercial wood fillers, which we will cover further in the article. You can also make a homemade filler on your own using items you have in your workshop or garage.

In some ways do not use wood fillers. Those include removing cracked edges and placing bow-tie inlays. We will get to them in a little while.

How to stop a crack in wood from spreading
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Types of fillers for fixing cracking wood

The common types of wood fillers are the following.

Water-based wood fillers

These fillers are applied easily. They dry and clean up quickly. You can finish them with just a little sanding after application to get a smooth and clean wood surface.

Petroleum-based wood fillers

These fillers are already smoothed, so you don’t have to sand them after application. Due to the petroleum-based formula, they resist moisture better. But keep in mind that the wood crack is caused by shrinking due to gradual drying. Keeping the wood away from moisture eliminates the need to dry.

Epoxy resin fillers

Epoxy fillers are available in putty and liquid forms. They dry pretty quickly, depending on the volume used: the drying for sanding can take as little as 15 minutes. Epoxy resin filler fills cracks and holes properly and makes a good material for woods that have a slight decay in them.

It is a popular option that people use on tabletops to make the appearance better: the epoxy can be stained with different colors of your choice.

Powdered fillers

This type of fillers only fits small cracks, splits, and holes and does not go well with larger gaps. This is due to a lack of structural strength.

These fillers come in powdered form. The powder is mixed with water, stirred, and made into a paste. The paste is then used as a common wood filler.

Wood putty

Wood putty is already smoothed and made flexible. Much like petroleum-based wood fillers, it stands up to moisture and temperature changes. But remember that the composition of wood putty can harm raw wood!

Homemade fillers

You can make your custom wood filler with items you probably already have in your workshop. They usually go well with small cracks and not with larger ones. It does make a good material that is inexpensive and effective in some situations.

You can make these fillers from some wood glue (e.g., white glue) and sawdust. We will give you a short recipe for making this kind of filler later in the article.

How to fill the crack in wood guide

Most wood fillers and epoxies are in liquid form, so they are better suited to filling cracks that are thin and long. The liquid can reach all the nooks and small corners once poured into the crack. But there are some differences between various kinds of products, and you need to be aware of them.

Wood filler

A great choice for wood with wide cracks and gouges. You can sand the wood filler after it has dried completely and paint it to match the rest of the wood piece.

Epoxy resin filler

If you are dealing with cracks that are deeper and thinner, you should use epoxy fillers instead. They are thinner and can seep into deeper areas in wood fiber in the crack. They also form stronger bonds with the wood grain in the crack. More than that, epoxy fillers are harder once dried and more durable than wood fillers.

Preparations

Once you have chosen your type of filler, prepare for the work. Epoxies can be toxic, so you should be wearing a respirator mask and work in a well-ventilated area or outdoors. It is also advised to wear rubber gloves if you are working with toxic chemicals.

Step-by-step guide

1. Prepare the workpiece

Whether it is a piece of furniture, wood trim, or something else, the workpiece should be dry and clean. Remove all dust or dirt if there is any.

2. Knife it or pour it

If you are using a non-liquid filler, take a putty knife and push the filler into the crack with it. Try to apply as much pressure as is needed to fill the crack completely. Do not worry if it sticks out a bit and the surface is not completely smooth. You can always sand it smooth after it has dried without using a putty knife.

If you are using a liquid wood filler, make a proper mixture and just pour it into the crack. Apply it generously to ensure that all the little crevices are covered. Again, it’s not a big deal if the surface is not smooth right away – you can sand it afterward.

And if you are using a liquid epoxy filler, just pour it along the crack and wait for it to seep into the nooks fully. The epoxy has two parts – the resin and the hardener, and they need to be mixed thoroughly, so you can fill cracks with a single pour.

If you want to stain the epoxy filler, then you should do it right now.

3. Dry time

The drying time depends on the kind of product you are using. You can read about it in your manufacturer’s recommendations. Epoxy usually dries faster than wood fillers. You can sand each material to get a smooth and clean wood surface. Wood filler can be stained and painted afterward.

How to stop a crack in wood from spreading
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Home-made filler recipe

If you choose to make your wood filler, here’s a simple recipe you can follow.

The two main components of the homemade filler are Elmer’s wood glue and sawdust. If you have a woodworking shop, you should already have those handy.

It is better when you have some wood dust that comes from your self-made piece of furniture or other woodwork. Or you can find some sawdust that fits your commercial wooden piece well enough.

Here are the steps to take:

  1. Mix the wood glue and the sawdust into a paste. If you have a wider crack, the paste should be more solid; if the crack is deep and long, you should make the paste more liquid.
  2. Apply the paste to the crack. Take a putty knife to push the filler deeper and correct the surface.
  3. As an option, you can fill the crack with wood glue only first and then apply sawdust to the glue surface. Use your fingers to press the sawdust deeper. But this way is messier, and once you sand the surface, the glue under the dust might show up. So making the paste first and then applying it with a putty knife is way more convenient.
  4. Allow the paste to dry up – it takes at least 24 hours.
  5. Sand the surface using fine sandpaper. Then paint or stain it, so it matches the wooden piece’s texture and color.

2 more ways how to stop cracks in wood from spreading

If you are curious to try out other methods to stop cracks in wood from spreading, we can give you a couple of them below.

Remove cracked edges

If the crack is situated on the edge of your wooden piece, you can just remove the edge using a saw.

These are the materials you will need:

  • Pencil
  • Ruler
  • Table saw (or miter saw)
  • Sandpaper

Take these steps:

  1. Draw a straight line parallel to the crack;
  2. Use a miter saw or table saw equipped with a crosscut sled to cut along your mark;
  3. The cracks can be deeper than they seem. Use something thin and narrow to measure the depth of the cracks. This way, you will know what you are dealing with.
  4. Sand the surface using sandpaper to get a smooth finish.

Of course, in many cases, you do not want to lose a part of your wood piece, so this method is for specific situations.

Bow tie inlays

Besides removing the material, how do you stabilize cracked wood? Bow tie or butterfly joints are templates that you can use to stabilize wood cracks. If the crack is large and located in the middle of the wood, you can use them since they simplify a difficult reparation process.

Here are the materials you need:

  • Inlaying kit
  • Plunge base
  • Double-sided tape

And here are the steps to take:

  1. Attach the template to the wood using double-sided tape to route the mortise. Then set the needed depth while following the template lines. Keep removing wood until you have a bow tie-shaped gouge perpendicular to the crack.
  2. Rout the bow tie and disconnect the guide bushing. Use the same template to make the inlay itself. The mortise should be as thick as the wood piece or a bit thicker than that.
  3. Now glue all exposed surfaces of the wood and attach the inlay. Wipe off any excess glue that sticks out when you insert the inlay into the place.
  4. Let the wood glue dry and fix the inlay in place. Take sandpaper and remove any excess materials.

Choosing the method that suits you best is up to you!

Why does wood crack?

The main reason for cracking over time is shrinkage, which is caused by wood drying out. But the wood dries unevenly: it dries twice faster along the growth rings than across them. So, the shrinking becomes uneven, eventually causing splits and cracks.

It is natural and inherent in the wood phenomenon.

But there are some other reasons for wood cracking that are not inherent in the wood itself. Water content, moisture, and wood age all determine how fast the wood will crack.

When it rains and the wood is open to lots of water and moisture, it will expand when contacting it. Then the lumber will dry out and crack while contracting.

The heating and cooling cycles are another reason for cracking, even if the wood is located indoors. When the winter begins, the heater is turned on, heating and drying the air. As the air loses moisture, the wood loses it too.

If you are especially worried about this problem, you can move the wooden piece away from the heater. The optimal humidity level for preventing wood cracking is about 50-55%.

How to stop a crack in wood from spreading
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How to save the wood from further damage and cracking

The main method of preventing cracking is sealing the wood. It will prolong your need to fix the cracks and keep them from spreading further. Applying a sealant prevents moisture from entering and exiting the wood, thus preventing any drying out or moisture level fluctuations.

Sealing the entire furniture surface is important. If, as an example, the tabletop is sealed while the ends and the underside of the table are not, cracks will form.

Some oils can be great sealers. The most common oil sealers are Danish Oil, Teak oil, Tung oil, and linseed oil. Linseed oil use is less widespread. They do not harm the wood texture and color.

Shellac is also a great option that offers about the same level of protection from moisture.

The other two materials that make good sealers are polyurethane and film finish. These are plastic coatings that prevent any water or moisture from getting inside the wood.

Other important questions (FAQ)

Do cracks in wood get worse? Can you prevent wood cracks from spreading?

There are multiple ways of preventing cracks from getting worse. We’ve covered all the basic ones in the article, and here’s a summary: using wood filler or wood putty; using sawdust and wood glue (home-made filler); using epoxy resin; using bow tie inlays; removing the cracked wood edges if possible.

What causes wood to crack?

Wood usually cracks because of its age, shrinking due to the drying process, and some environmental factors like humidity, tree wounds, bacteria, etc.

Can wood putty prevent cracks from spreading?

Yes, putty can prevent cracks from spreading in wood. Wood putty does not commonly show adhesive activity. But you can still use it to fill small cracks or long and thin cracks. You can also stain it, so it matches the wood color and texture.

Can you use sawdust and wood glue to stop cracks in wood from spreading?

Yes. Some people call it a self-made wood filler, and it can be effective enough to fill cracks in wood and stop the cracks from spreading. You also have the opportunity to pick the glue that matches the wood color. White glue is usually the best one for this purpose.

How do you stop wood from cracking further?

A common method of preventing wood cracking and sealing is applying boiled linseed oil. You can also use a sealant like Anchorseal, but it can be pricey. Some other effective sealants are shellac, Danish Oil, Teak oil, and Tung oil.

How to avoid wood cracking when nailing?

As always, there are a few ways of doing it.

The first method. Turn the wedge into the punch and hit it with a hammer before inserting it through the nails. It will create a small space between the nail and the wood. And that helps reduce splitting.

The second method – putting nails close to the same wood grain line. This will help avoid cracking, too.

Using a lubricant (petroleum jelly) reduces friction when nailing, which again decreases the chance of splitting, no matter which method you are using.

Also, keep in mind that nails with a larger diameter are more likely to cause splits than nails with a smaller diameter.

How to fill wood cracks? Can you seal a crack in wood?

Filling a crack is possible by using a wood filler, wood putty, sawdust and wood glue, or epoxy resin. Your choice will depend on your exact purposes.

It’s best to use wood fillers for long cracks. Sawdust and wood glue are more suited for shallow and wide cracks. Epoxy resin is more suited to large gaps and cracks.

Conclusion

Now you know how to deal with cracks that occur in wood, how to stop a crack in wood from spreading, and how to seal the wood, so it does not crack again.

Most cracks can be fixed and prevented, so you do not have to throw your furniture out if it has some of those in it.

We want to remind you that you should be using all the protective gear required for your work and stay safe.

Happy woodworking!

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