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How to Install a Single Internal Door

Installing and fitting new doors can add a touch of style and a professional finish to your new interior design. Not only do modern internal doors look great, they can also make your home feel more cosy and welcoming, and improve your property’s energy efficiency too. A good quality door will save you money over its lifetime by significantly cutting your heating bills.

In this comprehensive guide, we will walk you through the process of replacing a standard internal door. This tutorial covers essential steps, from measuring the door’s size to discovering the ideal placement for hanging. If you’re wondering how to fit a door with precision, this guide has you covered.

Which Door Should I Choose?

There are dozens of different door styles out there, to suit period homes, contemporary interior design, and everything in between. The main things that you will want to think about are the style, the material, and the finish.

Panelled doors offer good privacy and look luxurious and elegant. You can stain, paint or varnish them to match or contrast with the rest of your décor.

Glazed doors are ideal if you want to let more natural light into a room. They can make smaller rooms feel brighter, airier and more welcoming.

Fire doors offer 30-60 minutes of protection in the event of a fire. Depending on the size and layout of your home you may be required to have fire doors fitted. Talk to your local authority for advice about this.

Most interior single doors are made of wood. Wooden doors can be solid hardwood, veneered, or hollow core moulded. The most affordable option is hollow core moulded, and these doors are sold either pre-painted, with a woodgrain or smooth finish, or ready to paint – making them ideal for people who have a colour in mind. Solid hardwood doors are durable and long-lasting, but tend to be a little more expensive. Veneered doors are a good compromise, as they have a hardwood veneer, but are lighter and use less wood to make, so they are usually more mid-range in price.

How Do I Measure the Space?

When you are shopping for a replacement door, make sure that you measure the size of the opening (from frame to frame) instead of measuring the existing door. This will ensure that the door is a good fit.

You should take five measurements:

  • Measure the width of the door at the top, middle and bottom, and take the widest measurement, in mm.
  • Measure the height of the door – taking the vertical side of the frame from the floor to top. Take into account a small allowance for the carpet or other floor covering. Measure the frame on each side, and use the highest measurement, in mm.

Doors, even hollow ones, come with hardwood lippings around the door edge and the outsides which can be planed or sanded to make the door fit into an opening if it is too tight.

There are several standard sizes of door, based on the most common openings. If you live in an older property your interior doors may not be one of the more common sizes, and you may need to get a bespoke door made. If you have very large door openings, then one option is to get a standard sized door, and add sidelights to fit the rest of the opening.

How Do I Fit an Internal Door? 

Some doors are supplied ‘ready to hang’ with all the hardware and fixings included. In other cases, when you buy a door, you just get the door, and you will need to fit the handles, etc yourself. These instructions assume that you are buying a door slab that will be hung in an existing frame.

Usually, if you buy a standard-sized door, it will be a tight fit in a standard-sized frame, and you will need to trim a little off the height and the edge. Try to remove an equal amount of lipping from both sides of the door, rather than cutting down one side significantly.

You can make the job much easier if you use the same size of hinge on the new door as you did on the old one, since this means that you will be able to keep the original hinge, screw holes, and hinge positions. If you are unable to do this for whatever reason, try to stick as close as possible to the guideline positions – placing hinges 15cm from the top of the door frame, and 22.5cm from the bottom of the frame. If you need a third hinge to support a heavy door, place this in the middle between the other two hinges.

You can re-use your existing handles, assuming that the latch works well. If you need to replace the handle (or even just the latch), then this is usually easy to do – although you may need to make a new slot in the frame to accept the latch plate. When doing this, take care to chisel away from the body, and keep your hands well behind the cutting edge. If the original latch or the door hinges are stuck because they have been painted over, you can use a screwdriver to prise them off, breaking the paint.

Installing the Door: Step by Step Instructions

  1. Measure and Purchase a New Door: Measure the dimensions of the existing door, including width, height, and thickness. Purchase a new door that matches these dimensions.
  2. Gather Tools and Materials: Make sure you have all the tools and materials listed above before you start the process.
  3. Remove the Old Door:
    • Open the old door.
    • Remove the hinge pins by tapping them out with a hammer and screwdriver.
    • Carefully lift the door off its hinges.
    • Check that the doorframe hinges are still good for use
  4. Remove the Hinges:
    • Use a screwdriver to remove the hinges from the door.
    • Check if the hinges are in good condition; if not, consider replacing them.
  5. Prepare the New Door:
    • Place the old door on top of the new door.
    • Trace around the old door onto the new door to ensure the correct dimensions.
    • Trim the new door if necessary (see below)
    • Use a pencil to mark where the hinges will go on the new door.
  6. Install New Hinges:
    • Place the new door flat on a stable surface. Keep the door steady by securing it.
    • Align the hinges with the hinge recessess on the door. If the door doesn’t have hinge recesses, then you’ll have to measure the old door’s hinge positions to make sure it will fit in the frame.
    • Mark the screw holes for the hinges on the new door.
    • Use a drill to create pilot holes for the screws.
    • Attach the hinges to the new door.
  7. Install the New Door:
    • Place wooden shims on the floor to lift the new door slightly (about 1/8 inch) off the ground.
    • Insert the new door into the door frame with the help of a friend if needed.
    • Ensure the top of the door is level.
    • Insert the hinge pins into the hinges.
  8. Check Alignment and Adjustments:
    • Check the alignment of the door within the frame.
    • Adjust the shims as needed to ensure the door is level.
    • Open and close the door to ensure it swings smoothly.
    • Make any necessary adjustments to the hinges or shims for proper operation.

This is a general guide, and the specific steps might vary based on the type of door, frame, and other factors. Always prioritize safety and follow any manufacturer instructions provided with your new door. If you’re not confident in your DIY skills, consider seeking professional help for installation.

How to Fit A Door: Trimming The Door

Planning Your Door Fitting

  • When you’re ready to replace an internal door, align the new door hinges with the existing hinges on the frame. If you need to replace the hinges, they should be approximately 150mm from the top and 225 mm from the bottom of the door, as well as a centre hinge for stability. You can use a tape measure to make sure everything is in alignment.
  • Make sure the new door is the same thickness as your door frame.
  • Given the many different varieties of internal doors size, materials, and finishes, it’s important to pick a design that aligns with your requirements. Keep in mind that standard door might not match all door frames, especially in older residences. Because of this, you may have to trim your new door to fit within the existing frame.
  • If you have to trim the door, consult the manufacturer’s guidelines as the amount you can trim varies from door to door.
  • If you’d like to paint your door, check out our hub article on How To Paint Your Internal Door.

Fitting Your Door – But Doing It Right and Staying Safe

  • If you need to resize your door, make sure that all changes are made equally on each side of the door.
  • Be careful of wood splitting when trimming your door to size. This can happen when chiselling with the grain. Avoid this by making small cuts rather than large ones with a sharpened chisel.
  • Drill pilot holes before adding in any screws.
  • Wear safety goggles when drilling or sawing.
  • Wear gloves when handling timber.
  • Direct chisel movements away from your body.
  • Secure the door to a workbench, and lay the door flat while you’re working onit.
  • Be careful when lifting the door.

Door Fitting Aftercare

  • While internal doors generally demand minimal maintenance, it’s a good practice to keep them clean and free from dust and grime.
  • Only use products suitable for your door’s surface to ensure its longevity.

What Should I Do With The Old Door?

Once you have successfully replaced the old door with a new one, you have a few options for what to do with the old door:

  1. Reuse or Repurpose: If the old door is still in relatively good condition, you might consider repurposing it for another project. Old doors can be transformed into all kinds of cool things; tables, headboards, shelves, or even decorative pieces. Get creative and see if there’s a way to give the old door new life.
  2. Donate: If the old door is in decent condition and still functional, consider donating it to a local charity store. Some organisations might be able to use it in their projects or sell it to raise funds.
  3. Recycle: Check if your local recycling centre accepts wooden doors. If the door is made of a recyclable material, you can dismantle it and take it to a recycling facility.
  4. Sell: If the door is antique or has some unique features, you could try selling it online through platforms like Gumtree, eBay, or local online marketplaces.
  5. Dispose: If the door is in poor condition and cannot be repurposed, reused, donated, or recycled, you may need to dispose of it. Check with your local waste management authority for guidelines on how to properly dispose of bulky items like doors. They might have specific procedures for large items or offer special pickups.

Before making a decision, assess the condition of the old door and consider its potential value for other uses. Additionally, always check with local regulations and disposal guidelines to ensure you’re handling the old door in an environmentally responsible way.

Final Thoughts

If you’re in the market to fit a new internal door, then you’re definitely in the right place. We have the products and the know-how to make it all happen!

Take a look at some of our popular internal doors below.

Want to learn more about fitting doors and DIY projects? Take a look at these popular hub articles!


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