Fitting interior doors – what rules should I follow?  

6 minutes

Many professionals offer installation of internal doors for a fee. While the use of such a service for a single door is not a major burden on the household budget, for several doors it is quite an expense. You might as well do it yourself, especially as the subject is not particularly complicated. All you need to do is keep a few rules in mind and follow reliable step-by-step instructions. 

When is the best time to install internal doors?  

If you are trying to install the doors yourself, remember to do it after the renovation work has been completed – after plastering, plastering, painting the rooms and laying the floor. You should also wait long enough (preferably several days) to make sure that the walls are completely dry. Knowing when to install interior doors will avoid the risk of staining or damaging the doors as well as the walls and floors. 

What will we need for door installation?  

What door installation tools do you need to make the activity go smoothly? Here’s a list of essential items:  

  • measuring tape,  
  • spirit level,  
  • protractor,  
  • wedges (plastic or wooden),  
  • drill,  
  • screwdriver,  
  • installation foam – preferably low-foam,  
  • hammer,  
  • carpenter’s glue,  
  • door struts,  
  • painter’s tape to protect the frame,  
  • screws, bolts and anchors. 

Some of the items in the list above should come with a door with a door frame, so check exactly what you already have and what you need to get.  

Choosing the right door size for the wall opening  

This buzzword is a bit of a subversion, as the optimum process is to first select the door you want to install in a catalogue or shop and decide on the size of the door, and then prepare an appropriately sized opening in the wall (we wrote about what the dimensions of a door opening should be HERE). Although this is technically the only correct order, there are still many people who approach this task from the end. So remember that the dimensions of the internal door are the first parameter we need to determine, and it is to this value that we will adjust the size of the wall opening accordingly.   

Assembly of the fixed frame  

Lay out the individual frame components on a clean floor. Do this gently so as not to damage or scratch the frame. Precisely connect the top beam to the side beams, ensuring that there are perfectly right angles at the corners. You can do this using screws, fasteners or glue. Place the frame in the opening and carefully verify that it is seated straight and evenly. Place spacer blocks between the wall and the frame and stabilise the structure with wedges and adjustable struts. Installation of the fixed frame requires precision, so check the horizontal and vertical once again using a spirit level. Fix the frame with dowels, placing them under the seal so as not to spoil the aesthetics. Fit the sash and make sure the whole thing works properly and looks good. After this test, remove the door and, at the level of the corners and struts, inject mounting foam and leave it to dry (preferably for 24 hours). After this time, remove the struts, wedges and any excess foam. 

Fitting an interior door with a fixed frame is quite an easy undertaking if you follow the steps precisely. We have included detailed step-by-step instructions on how to install a fixed frame HERE.  

Assembly of an adjustable frame  

The installation of an interior door with an adjustable frame starts with the installation of the frame. It may be packaged by the manufacturer already as an assembled whole or be in several parts that you have to assemble yourself. Lay all the components on a protected surface. Be vigilant and ensure that no object lying on the floor scratches the frame. Begin the assembly of the adjustable frame by connecting the top beam and the two side beams together. Use fasteners, glue, screws or clamps to do this. At this stage, it is crucial that the beams form right angles with each other in the corners. 

Once the frame is prepared in this way, insert it into the wall opening and carefully check – using a spirit level and tape measure – that it is evenly seated. If it is, use mounting wedges and stabilise the frame. Place adjustable spacers at the height of the upper and lower hinges and the handle. We can now put the sash on for a test to verify that the whole is evenly assembled. After this test and stabilising the frame with metal screws, we remove the door (the holes and fixing should be done under the seal, taking care of the visual aspect). Between the wall and the frame, at the height of the struts, inject mounting foam and leave it for 24 hours. The adjustable angles should be connected together with special fasteners and inserted; if the adjustable element is too wide – the tongue of the angle should be trimmed. If it happens that the foam sticks out, the excess must be removed. Wedges and spacers must also be removed.  

Fitting an internal door – what to look out for?  

Once the door frame is in place, the question arises as to how to install the internal door. We suggest what to pay attention to during door installation:  

  • mask the installation foam with frame mouldings,  
  • check the length of the leaf, if it is too long – shorten it (this advice does not apply to leafs with ventilation holes or slots at the bottom),  
  • the hinges may need to be adjusted – a screwdriver and allen key will come in handy for this,  
  • finally, install the handle or knob.  

Fitting interior doors is easy if you follow the instructions. They should be included with every door, but we also provide them HERE.