How to Repair Hairline Cracks in Wood Doors (4 Easy Steps!) (2023)

Last updated on March 12th, 2022 at 09:22 pm

One day soon after moving into our current house, I noticed streaks of sunlight sneaking through the front door. Notaroundthe front door. But literallythroughthe front door. About a dozen hairline cracks in the wood door, about 1-2 inches long in the wood.

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I had been meaning to repair these cracks for a few years, but…. Well, Life happens. This past fall, I renewed my intentions to tackle this project as part of our home’s fall maintenance checklist. I created this checklist to help my better prepare our house for the cold winter.

It made sense to do this in the fall. Obviously cracks in a door compromise the integrity of the door and allow cold air inside the house.

And those drafts result in less cozy, energy-efficient home and higher energy bills. BOOOOOO.

But life happened yet again, and I didn’t fix the cracks in my door.

This week though, I’ve kicked myself in the arse and finally got around to sealing up these hairlines cracks.

And once it was finished, I kicked myself again. It literally took only 15 minutes to complete. It was a simple and inexpensive fix. Why didn’t I do this sooner???

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Why Do Exterior Wood Doors Crack?

First of all, why are there even cracks in my wood door?Wooden doors develop cracks over time when the panels within the door aren’t free to expand and contract in response to changes in temperature and humidity.

(Video) Filling cracks in doors and trim

What makes these panels not able to move? It’s layers of finish or dried paint that build up over the years. They cement the panels in place, not allowing movement. And when there is a change in humidity and temperature, the wood continues to shrink and expand, but the the panel is stuck in place, creating cracks.

How Do You Repair These Hairline Cracks?

Hairline cracks, like the small ones in my front door, can be filled with a wood putty or filler. All are sold in small quantities at home centers, hardware stores, and online. (Larger cracks are a lot more complicated, and I’d look elsewhere for a solution)

Now, I’m going to be upfront with you. I’m no DIY expert by any stretch of the imagination. But I believe repairing hairline cracks in a wood door with wood putty or filler is likely just a temporary solution (temporary meaning a few years).

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Why?

The door cracks because there still are built-up layers of paint or finish that don’t allow the panels to move. The only way to stop future cracks is to completely strip off the layers of finish, repair the panels, re-stain and finish.

And that is much bigger job that I’m willing to take on. We plan on replacing this exterior door eventually (we are currently on a spending ban while on a single income). I’m excited for a new door and have even already researched the factors to consider when buying a new door.

Why do we plan on replace our exterior door, you might ask? Quite simply, it doesn’t match the style of our house. I’ve been learning how to trace the history of old houses, which includes learning about American residential architectural styles.

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Our house is a Foursquare, which falls under the Craftsman style of home. Craftsman doors traditionally have rectangular glass panes in the upper-third of the door with a thick piece of trim or moulding (commonly a dentil shelf) immediately below. And as you can see from the picture above, our current door has neither characteristic.

If the style of the door matched the architectural style of the house, I would probably take a stab at completely re-doing the door. But that’s not the case. So my goal is to provide a quick, easy, frugal solution to repair these hairlines cracks in the wood door and seal up my house from winter drafts.

(Video) Wooden Door - Fixing Cracked & Broken Panels - Easy, Low Cost (4K)

What is the Difference Between Wood Filler and Wood Putty?

You might have noticed above that I mentioned that “wood putty or filler” are perfect for repairing the hairline cracks in a wood door. These products have two main differences as per the first two products described in the below video.

  1. Wood putty remains flexible (i.e. non-hardening) and cannot be sanded, while wood filler dries hard and can be sanded;
  2. Wood putties are applied after paint and finish, while wood fillers are applied before paint or finish (sometimes over primed wood).

If you want to get deeper into the differences between putty and filler, I’d suggest you read Fine Homebuilding’s Deciding on Wood Fillers comprehensive article about the various types of wood fillers and puttys, their pros and cons, and how to pick the right one for the job.

Hairline Crack Solution: Minwax Wood Putty

For my wood door, wood putty was the best choice since I don’t plan to sand or re-stain my door.It’s easy to use, quick and permanent.

Since wood putty is applied after paint and finish, it comes in a variety of colors. Pick the one that blends in best with the door’s wood.I chose Minwax Wood Putty in Red Mahogany.

Why Minwax? A few reasons.

  1. I’ve been very satisfied with other Minwax products, especially their interior stains;
  2. With 10 different colors of wood putty to choose from, Minwax provides one of the largest selection of colors I found online. Their wood putty is color-matched toMinwax Wood Finish stains to make wood repairs easier.
  3. Honestly, it was a good price on Amazon.
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Who is Minwax? Minwax offers a variety of woodworking products for preparing, staining, finishing, cleaning, maintaining & repairing wood.

Sounds like the soup to nuts on the wood niche, isn’t it!

But Minwax didn’t get its start with woodworking products. Instead, it was the result of a messy waterproofing job that altered Minwax on the course towards becoming one of North America’s top woodworking supply companies.

Minwax started about a 100 years old in Brooklyn, New York. Arthur B. Harrison convinced his employer at the time to test and manufacture his new waterproofing and damp-resistant materials to keep moisture out of homes and buildings (he later bought the business).

(Video) Woodworking Tip: Finishing - How to Repair Wood Cracks

Years later, Arthur, an acknowledged expert in the field of waterproofing, was called upon to help seal Cleopatra’s Needle in Central Park. This Egyptian obelisk, thousands of years old, was deteriorating from the change in climate from the desert to North America.

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A wood scaffold was erected around the monument for the project. While brushing on the waterproofing solution, the workers noticed that drips and spills on the scaffolding beautified the wood. In fact, the scaffold looked like it had been treated to a paste wax finish, yet it was not slippery to walk on.

And just like that – Wa-la! A new product was formed. Seeing its potential, Arthur refined the formula and introduced it to architects who incorporated it in design specs for wide use on floors and woodwork in public buildings and fine homes.

Side Note on Wood Fillers

As a side note, I have used wood filler on my interior doors. Why did I use filler instead of putty on my interior doors? My interior doors appear to be original to the house. They are solid, ridiculously heavy, and I plan on keeping them as long as possible.

Some are in great shape, some not so great shape. Over the past few years I’ve been slowly (veerrrryyyy slowly) have been sanding, repairing and painting them.

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To repair the years of nicks, gorges, and cracks on my interior doors, I use DAP’s Plastic Wood Professional Wood Filler. If you go the route of a wood filler versus putty in order to sand and paint your door, I have to give a shout-out to DAP’s wood filler.

OK – back to my project. Ready to repair those hairline cracks in your wood door? Let’s DO THIS!

How to Repair Hairline Cracks In Wood Door

Supplies

Instructions

REMEMBER: Test filler on a small inconspicuous area of the door first. Personally, I have problems matching stain colors, so I had to test a spot and let it dry to make sure it matches.

1. Set up your work area and protect your floors

Placed a towel or large clean rag on the floor near the door to lay out all the supplies. You don’t want to try to clean dried wood putty out of carpet or up off wood floors.

(Video) See how Easily you can repair WOOD Cracks & Knots

2. Ensure the door is clean and dry

Do a quick clean of the door and its groves with a dust cloth. Or, if especially dirty, wash the door with a mixture of gentle dish soap and dry with a soft cloth. No need to get dust and dirt stuck in with the wood filler!

3. Press wood putty into the hairline cracks.

Using either a craft stick or your finger, apply the wood putty along the hairline crack. If you have sensitive skin, you might want to apply using gloves. Then using a toothpick, push the wood putty deeper into the crack. Keep filling until the putty comes out the top of the crack.

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4. Smooth and Wipe Excess Wood Putty

Using a damp cleaning cloth or rag, remove the excess putty from the crack and around.

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That’s it! How easy was that? No longer do I have hairline cracks in a wood door. No longer do I see sunlight beaming through my door in the afternoon.

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How to Repair Hairline Cracks in Wood Doors (4 Easy Steps!) (12)

FAQs

How do you repair a cracked wooden surface? ›

  1. Using 80 to 100-grit sandpaper, remove any loose debris from the cracked area. ...
  2. Using 100-grit sandpaper, lightly sand any raised or rough areas. ...
  3. Using a putty knife, spread a thin layer of patching material into the cracked area. ...
  4. Use 220-grit sandpaper to smooth the patched area and make it even with the surface.

Should you fill hairline cracks? ›

Since most hairline cracks don't affect the structural integrity of the slab, sealing the crack is the main goal of the repair. It's more of a cosmetic fix then when you're dealing with larger cracks. But it should still be done because small hairline cracks can open up over time if ignored.

Should hairline cracks be repaired? ›

The sealed cracks need to be patched, dried for at least two hours, and covered using a board or a plastic sheet. It is essential to cover the area for around five days. Every day, you need to lift the covering and sprinkle water on the surface. Hairline cracks are not a big deal.

Should you tape hairline cracks? ›

Hairline cracks across walls and doorways do not indicate a structural problem; they should simply be re-taped and painted.

Can you fix crack in door? ›

Medium and large cracks will require more than just wood filler or putty to fix the cracked door slab. In these instances, you'll need to use an epoxy adhesive or wood splines, depending on how severe the crack is.

Can you repair a cracked door frame? ›

Yes, you can! At times, the damage to a door frame may be extensive enough that you feel it would be beneficial to replace it altogether, but replacing only part of the frame can cut costs. To do this, you must remove the molding, cut away the damaged area and replace it with a new cut of wood using wood glue.

Can wood glue fix cracked wood? ›

If the break is a clean one you won't need to use filler, just squeeze a tiny bit of wood glue into the crack and clamp the sides together tightly. You should be good to release them in about half an hour, but I will often leave them for 24 hours just to be sure.

Why do wood doors crack? ›

Humidity and temperature changes are the main reasons. When humidity is high the wood absorbs the moisture causing it to swell and expand. In less humid months, typically winter, the moisture evaporates out of the door, causing it to contract.

Can I just paint over hairline cracks? ›

Prime the surface before applying paint to improve adhesion. Apply a fresh coat of paint and wait for it to dry off properly before adding a new layer of paint if necessary. For deeper hairline cracks, you may want to use a filler to fill up the cracks before applying a new layer of paint in the affected area.

Do hairline cracks get worse? ›

Hairline cracks in teeth can grow worse the longer you leave them untreated. To learn more about how to prevent this problem and save your tooth, schedule a consultation.

Can you use caulk to fill hairline cracks? ›

Use an adhesive caulk, or a pliable caulk, to fill the cracks. Put a bead of this caulk in the joint and press it in with your fingers. It is the only thing that will fill such small cracks. Scrape off any remainder, and finish up by cleaning the crack with a damp sponge.

What causes a hairline crack? ›

Hairline cracks are thin cosmetic cracks that are caused by temperature or humidity fluctuation. These fluctuations can result in plaster shrinkage or swelling, creating small fissures. Hairline cracks are simply an eyesore and can be easily fixed with a new coat of paint.

Why do hairline cracks reappear? ›

It is typical that domestic structures will be built without such movement joints. Cracks that form through initial settlement then become ready-made movement joints. This is why a crack will continually reappear, no matter how many times it is filled.

Are hairline cracks common? ›

Below are the most common normal foundation cracks. Hairline cracks – Hairline cracks, also called cosmetic cracks, usually form within the first year of a newly-built home. You might find them near windows, corners of your walls, floors, or at longer sections of your foundation.

Will paint hide hairline cracks? ›

The simple answer is yes. A quality paint, applied in a couple of layers, should take care of most hairline cracks and perhaps even some very small fine cracks. However, you do run the risk of the cracks getting worse if they aren't covered by the right paint.

What kind of tape do you use for cracks? ›

tesa® 5225 Crack Cover is a flexible self-adhesive tape which is used to cover cracks, seams and holes in walls before papering.

What is the sealer for a door gap called? ›

Weatherstripping effectively seals up the gaps all the way around the frame as well as the gap at the bottom of the door to prevent the transmission of unwanted elements when the door is closed. Weatherstripping can be used at exterior or interior openings.

Can you use filler on a door? ›

Fill, repair and restore internal and exterior wooden doors with these highly versatile wood fillers. Suitable for all types of solid wood and veneered doors, they effectively fill, cracks, splits, and holes to restore wooden doors and frames.

How much does it cost to fix a crack in a door? ›

The average cost of fixing a cracked door is between $100 and $300, depending on the crack size and depth.

How do you fix nicks in a wooden door? ›

How to Fix Gouges in a Wood Door
  1. Choose a Filler That Accepts Stain. ...
  2. Remove the Door From the Frame. ...
  3. Clean the Door. ...
  4. Scoop Out Some Wood Filler. ...
  5. Squeeze Hardener Onto the Wood Putty. ...
  6. Blend the Filler and Hardener. ...
  7. Install the Filler. ...
  8. Trim Away Excess Filler.

Will wood glue seal cracks? ›

Yes, wood glue will work for filling in gaps and cracks in wood. It dries clear, so you most likely will not even notice it. The wood glue is even less noticeable if you sand it after it has had time to dry.

What causes wood doors to crack? ›

Humidity and temperature changes are the main reasons. When humidity is high the wood absorbs the moisture causing it to swell and expand. In less humid months, typically winter, the moisture evaporates out of the door, causing it to contract.

Can you repair wood door? ›

Repair wood with polyester filler: Apply wood hardener and filler. To repair rotted door frame, first remove rotted wood with a 5-in-1 or other sharp tool. Then coat the rotted door frame area with wood hardener as shown. Mix polyester wood filler or Bondo wood filler and press it into the recess with a putty knife.

What is the easiest wood filler to use? ›

Water-based wood fillers are easy to use, generally don't have strong odors, and usually dry quite quickly, some within minutes. Most contain gypsum, cellulose, or wood fibers. They can usually be thinned with water if needed, and clean up with just soap and water.

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