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Installing the back door

A back door can also be installed independently – i.e., without a craftsperson – because no expensive special tools or special skills are required. However, focussed, planned work is important, because the entire "back door" system can only comply with the manufacturer's specifications for thermal insulation and other properties if the door system is installed correctly.

Detailed instructions for installing a back door are therefore essential for a smooth process

Material list

  • Building foam
  • Washers
  • Vapour diffusion open foil or trioplex sealing tape (or alternatively compriband)
  • Door frame screws
  • Vapourproof film
  • Acrylic / silicone

Tool list

  • Building foam gun
  • Spirit level
  • Stone or wood drill (6 bit)
  • Tape measure
  • Drill
  • Impact drill or impact wrench

In order for the masonry to be optimally prepared keep the following ready: adhesive, building foam and floor rails to be able to seal the back door perfectly. A vacuum cleaner should also be kept ready so that old plaster or adhesive residue can be removed immediately.

1. Preparation for assembly

The door system, which is usually delivered as one unit and consists of a door leaf and frame as well as various accessories, should be laid out in as structured a way as possible together with the required tools before starting the actual installation. In order to be able to install modern back doors made from uPVC, wood or aluminium with as little effort as possible, the door leaf should be lifted out of the frame in advance.

a) Taking the door leaf off its hinges

The door leaf for a modern back door can generally be dismantled without assistance. However, with a helping hand, lifting it out is easier and faster – the risk of damaging the door is also reduced. It is particularly easy to remove the back door when the door leaf is at a 90° angle to the frame. If it is tilted away from the frame, the lower hinge part of the frame detaches almost automatically from the upper hinge part of the door leaf (Fig. 1).

b) Preparations and material required to install the door

A back door often comes with protective foils and covers. The foils can remain glued over a large area in order to avoid damage during installation. However, they should definitely be removed from the outside of the frame. The other foils should be completely removed no later than three months after delivery, but preferably immediately after installation, since the binding agent contained in the adhesive can form permanent residues on the back door. In order to be able to ideally fit a back door frame, some materials that are often not included in the scope of delivery are required for installation (Fig. 2).

2. Insulating the frame

Before the frame can be installed, it must be prepared for one of three types of insulation. There are three levels at which the back door can be sealed.

  • On the one hand, an insulating layer can be attached to the inside of the frame. This insulation separates the outdoor from the indoor climate. This means that it must be vapour diffusion sealed, i.e., it should prevent the spread of water vapour. For this, a vapourproof film or acrylic grouting is used (Fig. 3a).
  • The middle sealing level is between the door frame and the wall. Insulating material like 1-component PU foam or filler like mineral fibre material should be installed in this space (Fig. 3b).
  • The outer level is the weather protection level. The insulation installed here must be vapour-diffusing and driving rain-proof for a long period of time. This can be done using special vapour diffusing foils or sealing tape. The joint can also be sealed with silicone after installation (Fig. 3c).

As soiling often occurs when working with building foam and adhesive, it is also advisable to have a bucket of water and a cloth to hand.

3. Inserting the frame

After the preparation, the frame can be installed in the embrasure opening. Aligning the door frame using a spirit level is arguably the most important step for a back door that fits perfectly. If the frame falls to one side, the door leaf closes or opens automatically after installation.

The correct fit is achieved by aligning it using washers, wooden wedges or small pressure pads that can be pumped up by hand to the nearest millimetre. The alignment should be checked on all sides using a spirit level.

4. Fixing the door frame into place

In order to hold the frame in its final position, it is screwed into the masonry. If the holes required for this have already been drilled into the frame, you only need to pre-drill the embrasure at the appropriate points. If the holes have not yet been made, the mounting holes are distributed as follows:

  • Mark two holes at an equal distance from yourself and the edge of the frame on the upper cross strut
  • Also drill four holes at the same distance from each other on the hinge side of the back door.
  • The lower and upper screws on the locking side must be at the same height as the screws on the hinge side.
  • The two inner screws are located just above and slightly below the locking system.

After pre-drilling the frame, the necessary holes should also be drilled into the embrasure – the holes just created in the door frame can be used as a kind of template to achieve a flush result. The frame can then be screwed into the masonry (Fig. 4).

The screws should be flush and should not press the frame onto the washers and wooden blocks introduced during installation to prevent warping after removing the placeholders.

5. Sealing and foaming the spaces

After all the screws have been attached, check how the back door hangs should be checked using the spirit level. The spaces between the frame and the embrasure can then be filled with building foam.

  • The foam is initially carefully applied at the corners and edges, then completely injected around all the sides. During this step, you should ensure that you do not apply too much foam and that the foam has completely dried before you remove the placeholders in order to avoid warping of the frame after installation (Fig. 5a).
  • As soon as the foam has hardened, the back door can be sealed from the inside and outside. This can be done using cover strips or with silicone and acrylic (Fig. 5b).
  • In order to be able to attach or apply the sealant, excess building foam should be removed with a knife. Then side panels can either be attached and glued on or the existing joints can be grouted using acrylic. Sealing using silicone is recommended for joints that may be exposed to standing water (Fig. 5c).

After application, acrylic can be sprayed with a mixture of water and washing-up liquid and then pressed into the joint using your finger. A smoothing spatula is used to remove excess insulation layer residue.

6. Installing the door leaf

This step is easiest to do if you have a second pair of hands. For installation, the sash for the back door must be placed in the middle of the frame. You can then install the door leaf parallel to the frame (Fig. 6). Once it sits in the hinges, the locking pins are inserted. You should now check how the door hangs and adjust it if necessary. windows24.com also provides helpful tips for installing the back door.

When all the steps have been carried out carefully and the door leaf has been ideally adjusted, the back door installation is complete and it will provide reliable protection against weather conditions and possible break-in attempts.

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