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

One day soon after moving into our current house, I noticed streaks of sunlight sneaking through the front door.  Not around the front door.  But literally through the front door.  About a dozen hairline cracks in the wood door, about 1-2 inches long in the wood. 

How to Fix Small Hairline Cracks in Wood Door with Wood Putty.  Why do wood doors crack? #woodendoor #cracksinwood #fixdoor
Hairline crack at top left & bottom corners

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???

Step by Step Tutorial on How to Repair Hairline Cracks in Exterior Entry Door #frontdoorrepair #easyhomeimprovement #minwax #hairlinecrack

This post contains affiliate links, including but not limited to, Amazon Associates. As such, I earn from qualifying purchases. Full disclosure located here.

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.

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).  

How to Fix Hairline Cracks in Wood Door Panel Using Wood Putty #woodputty #cracksindoor #DIYwithMinwax #wooddoorfix

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.

Why do wood doors crack? Our mahogany front door. Nice door, but the style does not match our Craftsman home (in my opinion). #tiredfrontdoor
Our mahogany front door. It’s a beautiful door, but the style does not match our Craftsman home.

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.  

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).
Courtesy of YouTube

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 to Minwax Wood Finish stains to make wood repairs easier.  
  3. Honestly, it was a good price on Amazon.  

Who is Minwax? Minwax offers a variety of woodworking products for preparing, staining, finishing, cleaning, maintaining & repairing wood. 

Minwax 13613000 Wood Putty, 3.75 oz, Red Mahogany

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).  

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.  

How to Repair Small Hairline Cracks in Your Front Wood Door #doorrepair #woodworking #crackeddoor

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. 

Dap 21506 Plastic Wood Filler, 16-Ounce

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.  

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.  

Apply wood putty with a toothpick to get in the grooves of wood panel for exterior door #minwax #woodputty #quickfix
Apply wood putty with a toothpick to get in the grooves of wood panel for exterior door

4. Smooth and Wipe Excess Wood Putty 

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

Exterior door repaired with Minwax Wood putty in Red Mahogany color #minwax #crackeddoor #woodfiller
DONE! Hairline cracks in my wood door filled!

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 fix cracks in old doors using wood putty easily and simply #DIYfix #simplerepair #wooddoor

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