How to fit a pre-hung doorset

A pre-hung doorset  is the term given to a door which comes ready-assembled in a frame, and often has most of its hardware already fitted. This can also be called a door set or door assembly. They will usually be more expensive than buying the separate parts, but should be significantly easier to install. Make sure you follow the manufacturer's instructions for individual door sets. Measure the rough opening carefully before you order you doors so you can select the correct door set. These should already be set straight, level, and plumb ready to be installed with minimum effort. For more information see: How to measure for a new door set

Always remember that when an external door frame is being replaced, like when you're installing a ready hung complete doorset, it will be considered a 'controlled fitting' under current Building Regulations. This means you'll have to notify Building Control of your plans or you can use a 'competent person who will be familiar with the Regulations you need to follow.

Step 1 - Check door set

You should check the pre-hung door  when it first arrives so you can report and fix any problems straight away. All hardware and fixings should be in the right place and working correctly. You should also place the door set against the rough opening to check it is the right size, known as dry fitting. You also need to check if it requires any treatment before being installed or the guarantee for the door can be invalidated and the life of the door will be significantly reduced.

Step 2 - Remove old door and frame

For external doors, you should wait until the new door set and anything else you need is already on site before you remove any old doors. This will mean the opening is not secured for as short a period as possible. Once you are ready you can remove all the old door, frame, and architrave. For more information see: How to remove and old door and How to remove an old door frame and architrave

Step 3 - Unpack door set

Remove the packaging from the pre-hung door when you're ready to install it. This will include any temporary fittings which you'll often find holding the door shut within the frame for transport. You should clean and dust the opening. You want a clean opening to work in.

Step 4 - Install door set

Pre-hung doors can be particularly heavy, especially for external doors, and you might need help to install it. Only place the jambs of a pre-hung door directly on the floor if the floor is fully finished, with the correct flooring installed, or if the flooring will go around the jambs. If the door is external you'll need to make sure and appropriate waterproof barrier is installed around the opening where the frame will fit.

If the floor isn't finished you can use spacers to place the jambs on. The spacers can be something like pieces of plywood which are an equal thickness to what the flooring will be. The clearance for the flooring should have been taken into account during the measuring for the door set, and if the set includes a sill, you'll need the flooring to be in place when you install the door.  

Once the floor is ready with fitted flooring or spacers you can insert the frame carefully into the rough opening. Sometimes this is done with the door fitted to the frame, other times you should remove the door first. Directions should be given in any instructions. You should have enough space between the frame and the wall for you to make slight adjustments – this will help you get the door and frame straight, level and, plumb.

Step 5 - Adjust door set

Push the frame in so that it's flush with the wall, or about 1mm proud of it. This is so the architrave will fit correctly with no gap between where it meets the actual frame. Any gaps between the wall and architrave can be filled. Insert suitable packers or shims around the frame so it fits securely in the opening. Use a hammer to knock them in if you need to, and use a spirit level to check all the sides of the frame remain level. 

You should see an equal gap between the door and the frame all the way around. This is usually about the thickness of a two pence piece. If it is not equal, you should adjust the frame within the wall until it is. Any adjustments can be made by inserting more shims or packers. Use them to push out sections of the frame slightly wherever it's needed. Keep checking with the level until all sides are correctly lined up. 

Step 6 - Fix to wall

Fix the frame to the wall with appropriate fixings, these will usually be indicated in the specifications of the door set. They must also be suitable for use with the type of wall you are fixing them too. You should drill starter holes for all fixings to prevent the frame from splitting. 

You will usually use about five to ten fixings on each jamb, but it will depend on individual doors, so always check. You should try to place the fixing equal spaces apart and at a minimum of 150mm from the bottom and from the top. 

Keep checking that the frame is completely level as you place each fixing as it can move slightly every time a new fixing is installed. You may need to remove some seals or other parts of the frame to attach fixings. It's usually recommended to remove the centre screw on the hinges and replace it with a fixing which will go through the frame to the wall. Check specifications to see if there is a particular hole in the hinges of your door you should use for this.

Step 7 - Finish

Once the door is secured all around you can trim or snap off any packers or shims which protrude, making sure they're flush with the wall. If it's an external door you should fill the space between the frame and the wall with an insulating sealant so it's fully weather proof. If you need to, you can now re-attach the door and any seals or fittings you removed during installation. 

Finally, you should check that the door and any hardware are operating correctly. If the gaps around the door and frame are correct the door should open and close easily with not parts sticking. The door set should now be ready to have any architrave, other trimmings, or any additional hardware fitted.

For more information see: How to fit door architrave