Guide to Trimming Hollow Core Doors

Do you know what type of interior doors you have in your house?

Most likely, they’re hollow core doors, since these are the most popular internal doors in use today. Even so, the phrase ‘hollow core door’ may not mean anything to you. In this guide, we’ll aim to answer the main questions we get about hollow core doors, including how hollow core doors are structured and the pros and cons of hollow core doors. We will also look at important information about trimming down hollow core doors so they can fit snugly into your doorframes. We’ll cover how to resize hollow core doors, best practices for cutting a hollow core door and how much you can trim off a hollow core door. 

*Check out our range of external and internal doors from Aspire!*

What is a Hollow Core Door?

Wooden doors come in three types: 

• Solid wood
• Solid core 
• Hollow core

As you would expect, solid wood doors are made from thick slabs of wood. They are strong, secure and are good insulators. A solid door is also rather costly which makes them a natural choice for external doors. 

Solid core doors have a thin veneer of high-quality natural wood fixed over a core of engineered wood, such as HDF. 

Hollow core doors, contrary to their name, do not have an empty void at their centre. Instead, they have a thick solid frame and a core made of plastic or cardboard. This core is usually constructed in a hexagonal ‘honeycomb’ pattern; one of the strongest structures found in nature. This makes the doors more solid, robust, and soundproof than if it was truly hollow. 

Hollow core doors are lightweight, easy to fit and inexpensive, which makes them a popular choice for internal doors. They are also very versatile. This honeycomb core can be contained within a variety of veneers that can be matched to any decor. They can even be made to resemble far more expensive solid wood doors.

Why Might You Need to Trim the Door?

There are loads of reasons you might want to trim the door. There may be too much wood in the way of the carpet, or you may need to fit an old door into a new frame. Many doors may need to be slightly trimmed in order to fit in your home.

Some of the most common reasons for trimming doors are:

1. Improper Fit: One of the most common reasons to trim a door is that it doesn’t fit the door frame correctly. This can happen due to various factors, such as changes in the door frame’s dimensions, settling of the building, the use of a non-standard door, or simply ordering a door and finding that it doesn’t fit the frame!
2. New Flooring: If you install flooring that is thicker than your original flooring, you may need to trim the bottom of the door so that it clears the new surface.  
3. Custom Door Frames: If you have custom-sized door frames or openings, you may need to trim a standard-sized door to fit properly.

Additionally, you may have an awkward door frame in a non-standard size that makes purchasing a new door incredibly difficult. You could estimate the size or even misread your tape measure. Mistakes occasionally happen, and can mean that when your new door turns up it’s an inch too tall for its frame.

You may even need to resize old doors. 

Can Hollow Core Doors Be Trimmed?

Because of the “hollow” nature of these doors, there are some precautions to take when trimming; But hollow core doors can, in fact, be trimmed!

Hollow core doors have a strong block outer frame, which leaves a couple of inches of solid wood at the top, bottom and sides of the door. When it comes to allowing for alterations, this frame makes them a lot more forgiving than you might think. This counts for the sides as well as the bottom and top of the door. 

This answer does come with a ‘but’ though. If you cut off too much of the door’s top, bottom or sides you could damage it’s structural integrity.

How Much Can You Trim off a Hollow Core Door?

Removing an inch or so from a hollow core door to allow for a thicker carpet, misread tape measure or wonky doorframe will be fine. 

However, cut off too much – roughly over 2 inches – and you may notice that the edge of the door is no longer solid. As such, while it is possible to trim hollow core doors, it isn’t always advisable to cut them down if serious alterations are needed. 

If you’re unsure of how much your door can be trimmed, ask your supplier for its trimming allowances

If too much is cut off the edge of a hollow core door, the structural integrity of the door can be compromised. This can be fixed by reinserting a block from the bottom of the door inside the veneer using glue. 

Though this may sound simple, it can be fiddly. There is a lot of potential for it to go wrong, leaving you with a door that is even more unsuitable than it was before. In general, it’s advisable to avoid going to these extremes. 

That said, if all you’re looking to lose is a thin layer from your door, then read on for a quick guide on how to trim hollow core doors.

How to Cut a Door to Size: Hollowcore Edition

What you need to trim hollow core doors:

• Sheets or paper to protect the surface of the door
• Tape measure or something with a straight edge
• Masking tape
• Guide wood
• Utility knife
• A saw blade (a jigsaw or circular saw will work)

How to Trim a Hollowcore Door to Size

The first step is to remove the door from the frame. This can be done by removing the hinge pins, beginning at the bottom, then working your way up. Then we can move on the the main attraction: Trimming the door!

1. Measure up

Measure how much you want to shave off the door.

Measure the door frame in three places: along both sides and the middle. This will give you the truest possible reading and minimise the risk of mistakes. 

Remember, you only have about an inch and a half available to lose from the average hollow core door. 

If you need to take off more than that, think about replacing the door instead.

1. Mark the door

Start by drawing a pencil line to show where you’re cutting. Use something with a straight edge like a ruler or tape measure.

Use a knife and a guide to create a cutting line. This helps stop the door from splintering when you start sawing it and helps you adhere to a straight edge.

1. Mask the door

Wrapping masking or painter’s tape around the bottom of the door will also help prevent chipping or splintering. Another tip is to wrap the foot of a circular saw with tape, as this can protect the surface of the door from damage while the saw blade does its thing.

4. Cut the door

The big moment. You can use a hand saw or a circular saw here. Use the cut line as a guide and keep the saw steady to ensure a clean straight edge.

5. Sand the door

Use fine-grit paper to lightly sand off any rough patches on the cut edge. A hand sander will obviously make this job quicker and easier but try to be gentle and restrained, or you may wind up losing more height on the door.

6. Minor Adjustments

Obviously, what you do here will depend on the door’s appearance. You may need to make some additional minor adjustments, such as repainting the bottom of the door. Ensure they are completely dry before you re-hang them. This will benefit your door and your carpet. 

7. Rehang the door

Rehanging an internal door is a simple task with two people. Take the door and very carefully fit the hinge side of the door into the frame. Have one person hold the door in place, while the other person hammers in the hinges. Begin with the top hinge, then move to the bottom and middle hinge. This will keep the weight of the door from bending the hinges.

Final Thoughts

Trimming hollow core doors is possible, but not always easy. It can take a seasoned DIYer, particularly if you’re trying to lose a lot of width or height, and it can be intimidating if you don’t have the right tools.

Hopefully, this post will have helped you trim internal doors on your own!

Interested in learning more about internal doors? We have a wealth of knowledge on our site. Check out some of our favourite informational articles here:

• How to Fit an Internal Bifold Door
• How to Clean and Maintain your Internal Door
• Hardware for Internal Doors