TWN TI: A Revolution in Two-Stage Flat Roof Drainage

The conventional installation of the second stage of drainage is relatively complex, imprecise, and involves multiple steps. Unfortunately, it also includes several potential points of error that may compromise roof integrity or reduce the functionality of the roof outlet. This issue is now addressed by our innovative product — TWN TI.

Classic installation of the second drainage stage (TWN Extension)

After completion of the protective roof layer, i.e. the vapour barrier, one or more layers of thermal insulation are installed in various forms, such as polystyrene boards. Once all insulation layers, as well as the separation and protective geotextile layer, are installed, the main waterproofing layer follows (most commonly mPVC membranes).

At the drainage point (roof outlet), it is necessary to leave or cut an opening in the thermal insulation for installation of the TWN extension. In most cases, this opening has a rectangular shape (cut using a saw or by omitting insulation boards) and is larger than the dimensions of the extension itself. After installation of the TWN extension, it is recommended—where possible—to fill the remaining gaps between the extension and the thermal insulation with foam.

Another demanding step is the standard recommendation to lower the TWN extension by 20–30 mm below the surrounding waterproofing level to ensure optimal water drainage. This height reduction must be created within the thermal insulation, which is both time-consuming and labour-intensive.

To eliminate these shortcomings and simplify installation, we developed a heat insulating element that effectively resolves the issues described above.

Heat insulating element TWN TI

Many of the challenges associated with conventional two-stage drainage installation are solved by our new heat insulating element. It significantly speeds up and simplifies installation by completely eliminating the need to modify or create openings in the thermal insulation. The roof outlet extension is inserted directly into a precisely shaped recess in the polystyrene insulation board.

The heat insulating element made of EPS 150 expanded polystyrene is designed for roof outlet extensions and has dimensions of 600 × 600 × 100 mm. It is primarily intended for use in two-stage flat roof drainage systems with the following types of non-heated TWN roof outlet extensions: TWN v220, TWN v300, TWN v500.

Installation procedure for the TWN TI heat insulating element

1. The heat insulating element can be installed directly onto the vapour barrier layer. In cases where the thermal insulation thickness at the roof outlet location exceeds 120 mm, the element is placed onto the thermal insulation layer.
2. The heat insulating element replaces the thermal insulation at the location of the TWN roof outlet extension, therefore the insulation must be omitted in this area. The plan dimensions of the element are 600 × 600 mm, with a height of 100 mm.
3. We recommend anchoring the element to the load-bearing substrate at four points using telescopic fasteners. If the TWN roof outlet extension itself is anchored, separate anchoring of the TWN TI element is not required. The top surface of the product should be at least 20 mm below the level of the adjacent roof surface.
4. Installation then continues with placement of the TWN extension and the roof waterproofing membrane.

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Simplify and accelerate your projects with another reliable product from TOPWET. For more information visit our website www.topwet.com and do not hesitate to contact us for technical support or professional consultation.