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5 reasons why water on the roof stays behind after rain

Józef Baar
Menedżer produktu
zalegająca woda na tarasie z desek kompozytowych
Do you also have water on the roof terrace after raining in undesirable places? We explain the reasons why water on the roof terrace remains.
In this article you will learn:
Why can the water on the roof surface of the rooftop terrace persist for a long time
What can residual water on the terrace lead to?
How to deal with this problem

If you are concerned about the residual water on the roof top terrace, be sure to read this article. We will explain everything from scratch.

To start with, the terraces are divided into two basic divisions:

  • traditional terrace (wooden or composite on joists or made of tiles glued to the terrace base).
  • ventilated terrace (wooden or composite on joists or made of ceramic tiles 2 cm on support pads or adjustable pedestals).

If your terrace is installed using the traditional method, that is:

  • in the case of a terrace made of wooden or composite boards (boards screwed to the joists of the substructure and those based directly on the ground)
  • and in the case of terraces / balconies made of ceramic tiles permanently glued to the substrate with mounting adhesive

The first and most important reason for water on the roof top terrace retention on it’s surface is uneven ground or improper slopes. 

If it is the fault of the unevenness of the ground, it is no wonder that the water in the roof top terrace areas. It is not dependent on the top cladding. The fault is in the floor. And it is from its alignment that repairs should begin. 

The second possible reason is the poor quality of the finishing elements, i.e. boards or tiles.

If the terrace base has been properly prepared and the edges of the tiles are bent upwards or the boards are boat-like, the fault is on their side.

The cladding needs to be changed. This will solve our problem.

Traditional terrace bases are usually prepared with a slope towards the outer edge of the balcony / terrace / loggia or on roofs towards the downpipe, so if the screed was made in accordance with the construction art, the fault lies on the side of the top product. 

Third, remember that each material has its own strength.

The strength of a component is a numerical value for the weight of pressure that the material can withstand until it fails. The strength value is always provided by the manufacturer.

Often, the lack of knowledge of the value of the maximum weight that can be set on our deck's finishing surface causes damage to it.

The ceramic tiles break and the boards bend. Often even irreversible damage that necessitates replacement with new ones.

Be sure to familiarize yourself with the strength of the material you plan to install, so that you know how much weight you can put on your terrace / balcony / loggia.

The above examples where water is kept on the roof terrace also apply to ventilated terraces. Those placed on adjustable or support pads.

However, in this case, there are a few additional points to note:

When leveling terrace tiles or composite boards with the use of adjustable pedestals, it is important to meet all the parameters that determine the correct leveling of the installed terrace surface

And here:

Fourthly, the most important thing is to choose the right type of adjustable pedestals for the planned loads.

When it comes to the terrace development plans, we probably already have the final arrangement in mind.

If we know where we want to place heavy pots, grill or even a pool. It is good to strengthen these places.

Reinforcements are made by additional positioning of the adjustable pedestals. In this way, we will make another adjustable pedestals for the wooden or composite boards or ceramic tiles. And thus strengthen their strength.

The fifth and last important point to pay attention to.

The one that causes the water on the roof terrace to remain in inappropriate places are all the side elements of the structure

Regarding point 5 for water on the roof terrace and all othert terraces, we are talking here about:

  • rubber pads under the adjustable pedestals, e.g. made of SBR rubber pads
  • tape securing the joist
  • using the correct gap spacer when installing terrace tiles
  • using an adapter to screw the joists to the adjustable pedestals
  • whether to level the tiles of each tiles separately and with respect to each other.

Maintaining all technical parameters of adjustable plinths will ensure the correct leveling of each terrace surface. And a balcony. Also, there is no stagnation of water on tiles, boards or terrace ceramic tiles. Of course, everything is in accordance with the montage instructions.

It is always better to make a terrace with a slope from the building. Then the rainwater will be able to run off the surface freely. Regardless of whether they are composite or wooden boards or terrace tiles, the water will have a free flow, compatible with gravity. 

First of all, if the water stagnation on the ventilated terrace is caused only by the unevenness of the boards? Secondly, maybe it's the rustic nature of the boards?

Then there is nothing to worry about.

The system of ventilated terraces makes it possible to adjust the height at any time.

Re-level the substructure adjustable pedestals and enjoy the beautiful terrace.

However, if you have located the problem and it is in the construction, repair the problem immediately.

Don't allow further degradation.

This can damage the entire structure of the terrace as a result in the future, its destruction.

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