Wooden doors for exterior use - the solution for a strong bond

Of all the types of wooden doors, the most tried and tested are those for the exterior. Humidity and low temperatures in winter, high temperatures and the aggressiveness of UV radiation in summer are tests that doors have to face. In order to make them as durable as possible, they are made of wood with higher humidity than furniture wood, construction solutions are adopted that allow dimensional variation, varnishes and exterior adhesives are used. If the doors are made of solid wood with glued elements, then glue undoubtedly plays a very important role.

Natural aggressions to which exterior wooden doors are subjected

Let's take a closer look at what wood doors are subjected to and what this means for the adhesive. In winter, when temperatures drop below 0°C, the humidity drops very low. The reason for this is that water in the air turns to ice. The balance is broken and rebalancing is done using the available moisture. One source of moisture is water in wood. This is how cracks appear in wood in winter.

The stresses that occur in the wood due to water removal also put pressure on the glue lines. If they are not elastic, the solder can fail. When the glue is of good quality and suitable for the place and area of use of the object, the glue is strong and cracks will always appear in the wood, never in the glue line.

Summer is the enemy of the sun. If the door is dark and in the sun between 10am and 5pm, the surface temperature rises sharply and can damage the adhesive. It needs to be sealed with an adhesive with very high temperature resistance. This way, regardless of the temperature, the glue line will retain its characteristics.

Also important are the finishing materials and how they are applied. Protection on all sides, on both sides and edges, the use of semi-transparent products with pigment content, a lower gloss varnish, are "details" that can make a difference.

The solution found by Szolvegy Târgu Mureș for timber framed doors and planks

The most commonly used construction solution for doors is frame and panels. The panels are not glued but are fixed to the frame so they can vary in size depending on the humidity in the environment.

I have told you on other occasions that the best solutions are found when supplier and customer work as partners. That's what happened in this case. A door manufacturer was having problems in the summer with solid wood doors with a frame. Especially the ones in very dark colours. He asked the adhesive funder for help to solve the problem.

Solvegy Târgu Mureș specialists started from the idea that each of the door elements reacts differently under the action of the sun. The frame, being made of whole elements joined at the ends, needed a very elastic adhesive that would ensure a very strong bond. The panel, made by gluing several elements together, had to be made in such a way as to resist the aggression of the summer sun. A very strong adhesive was needed, which was totally 'indifferent' to any aggression it was subjected to.

The saving solution - combining the qualities of 2 adhesives

After tests they concluded that the best results are achieved by combining the qualities of 2 adhesives. They used a D3D adhesive for the frames, i.e. a D3 adhesive with improved qualities, and a D4 single-component polyurethane adhesive for the boards, with very good results on the outside.

It looks like they made the perfect choice because doors made this way never had any problems. The solution has also been proposed to other manufacturers who have thus significantly reduced the number of complaints during the summer. They are convinced that it is the best solution for such doors and recommend it with confidence to all customers.

Because they are superior adhesives and can be used successfully for other joints, a brief introduction to each one might be useful.

TISZABOND D3D adhesive

It is a polyvinyl acetate (aracite) based adhesive, which has reactive groups that improve its qualities. The adhesive has increased wet tack, frost resistance, even to repeated freeze-thaw cycles and the resulting film is softer and more elastic. Glued wooden elements can move in case of humidity variations without the glue line suffering. In wooden door frames this is very important because of the long sides. Dimensional variation is noticeable and the adhesive must be able to take it up.

It is suitable for demanding work such as producing indoor stair treads, kitchen worktops, folding chairs, restaurant chairs, sauna elements.

Can be used in construction for indoor bonding that is not subject to high humidity. As an example, it can be used for gluing wooden steps to concrete stairs.

TISZPUR Adhesive D4 4401 Special

It is a one-component polyurethane adhesive that reacts with moisture in the atmosphere. The resulting film is highly elastic, very adhesive and has very good resistance over time.

Its main quality is its resistance to outdoor conditions, where high humidity is one of the problems. For this reason it can be used in construction. Due to its very good moisture resistance it can also be used in shipbuilding.

The adhesive bonds wood to plaster, brick, metal or concrete without problems. Unlike other adhesives that are disturbed by water in the material, the presence of water in this adhesive guarantees a good bond.

Another area where TISZPUR D4 Special polyurethane adhesive can be used is for gluing exotic wood. It is already known that exotic wood offers all sorts of unpleasant surprises. The large variety of salts and tannins contained can lead to weakening of the glues. By using polyurethane glue this risk disappears.

Also in the construction sector, the adhesive can be used for bonding insulation materials in the form of tiles or mattresses. Regardless of the nature of the insulation material - expanded polystyrene, glass wool, plasterboard, wood fibre boards - The bonding is very strong and safe.

In conclusion

Doors used outdoors are subject to variations in air humidity, temperature variations, weathering and UV radiation. Therefore, when manufacturing wooden doors for outdoor use, the construction solution and materials must be chosen to resist these aggressions.

As for the adhesive, it must be very elastic and have high moisture resistance. Szolvegy has found the right solution by combining 2 adhesives with very good qualities. It is the solution that solved a customer's problems and that he recommends to all those who produce doors of this type.