A drop-down seal may look like a relatively simple door component, but the available solutions differ in construction, operating method, and intended use. A different solution is needed for exterior doors exposed to rain, another for interior doors where acoustic comfort is most important, and another for sliding or glass doors.
That is why, when choosing a threshold, it is worth starting not with a specific model, but with the answer to the question: what task should the seal perform and in what door will it work?
In the Alumaster range, drop-down thresholds have been divided into several groups corresponding to different applications – among others: IDROZERO, CHRONOSOFT and CHRONOCLICK, thresholds for sliding doors, Glassline systems for glass doors, and Aline thresholds.
IDROZERO – when protection against water is especially important
IDROZERO is a sealing system for the lower door area, intended for constructions in which, in addition to a flat passage, increased protection against water and weather conditions is important. It works well in places exposed to driving rain and wind, as well as in modernization projects where the existing floor cannot be disturbed, for example in some historic buildings.
The system combines an automatic drop-down seal with additional sealing elements for the lower corners of the leaf and frame. In a properly prepared construction and with correct installation, it can achieve watertightness up to class 9A according to EN 12208, corresponding to wind loads at a pressure of 600 Pa, without using a fixed threshold on the floor.
Depending on the variant, the solution can be used in PVC, timber, aluminium, and steel doors, including burglar-resistant constructions.
When is IDROZERO worth considering?
Primarily for doors:
- exterior
- exposed to driving rain and wind
- requiring increased watertightness in the lower area
- where a flat passage without a fixed threshold is needed.
Basic parameters of the IDROZERO family: profile cross-sections from 17.8 × 28 mm to 24 × 20 mm, lengths from 430 to 1530 mm, standard trimming range up to 100 mm. Clearance under the leaf up to 12 mm, seals designed for gaps from 8 or 10 mm.
CHRONOSOFT and CHRONOCLICK – when comfort and controlled dropping matter
CHRONOSOFT and CHRONOCLICK use a patented hydraulic delayed-drop mechanism. The seal lowers only after the door is closed, so it does not rub against the floor while the leaf is moving. This reduces noise and wear and helps protect floors and carpets.
CHRONOSOFT operates gently and silently, and full sealing occurs after about 5–8 seconds. It is suitable wherever quiet operation and acoustic comfort are important.
This solution may be especially useful in:
- hotels
- consulting rooms
- offices
- conference rooms
- apartments and houses
- rooms where acoustic comfort matters
- rooms where the flooring must not be damaged.
CHRONOCLICK makes a quick drop, after the door is closed, accompanied by a characteristic click. It provides a more distinct actuation of the mechanism.
Basic parameters of the CHRONOSEAL family: profile cross-sections 14 × 35, 15 × 30 and 25 × 20 mm, lengths from 330 to 1530 mm, trimming possible up to 150 mm and drop up to 12 mm. Depending on the model, acoustic insulation reaches Rw 51.5 dB, and fire resistance up to 120 minutes. Exact parameters should be checked in the documentation for the selected variant.
Drop-Down Thresholds for Sliding Doors
Sliding doors require a mechanism adapted to the horizontal movement of the leaf. After they are closed, the seal lowers onto the floor, and while the door is sliding it remains hidden in the profile.
Sliding doors require a mechanism adapted to the horizontal movement of the leaf. After they are closed, the seal lowers onto the floor, and while the door is sliding it remains hidden in the profile.
Basic parameters of the group: profile cross-sections from 8 × 20 to 18 × 30 mm, lengths from 330 to 1830 mm, trimming possible up to 150 mm and drop range from 10 to 14 mm. For selected models, confirmed acoustic insulation is up to Rw 41 dB. Parameters depend on the door construction and the specific variant.
Glassline – drop-down thresholds for glass doors
In glass doors, the seal remains a visible part of the construction, so it must be matched both technically and aesthetically. The Glassline line includes acoustic models, solutions with hydraulic delayed drop, and variants mounted directly on the lower edge of the glass.
Depending on the model, the seals are designed for glass thicknesses from 8 to 14 mm. They can be installed without drilling, using high-adhesion tape
Basic parameters of the group: lengths from 330 to 1830 mm, trimming possible from 50 to 150 mm, seal drop from 12 to 20 mm and acoustic insulation from Rw 32 to 50 dB – depending on the model and configuration. Profiles are available in several finishes, including anodized silver, stainless steel, matte black, and champagne.
Aline – universal drop-down thresholds
Aline is a group of thresholds intended for a wide range of standard door constructions. They can be used in doors made of:
- wood,
- aluminium,
- PVC,
- steel.
The mechanism operates automatically. When the door is closing, the activating element works with the frame, triggering the lowering of the seal and closing the gap between the lower part of the leaf and the floor or threshold plate.
The advantage of this group is its wide range of applications. Aline thresholds can be used both in new door constructions and, after checking installation feasibility, in existing doors.
Their use helps reduce the passage through the gap under the leaf of:
- sound,
- drafts;
- cold air;
- light;
- heat loss.
For this group, acoustic insulation is up to Rw 52 dB, with drop adjustment up to 14 mm.
Are There Other Types of Drop-Down seals?
The division presented covers the most popular products. There are many more possibilities. Depending on the project, solutions are also available for more specialized constructions, pivot doors, systems with increased acoustic requirements, or doors for which specific fire-resistance properties are important.
If you would like to learn about the benefits of using a drop-down threshold, the types of doors it can be installed in, and the key factors to consider when choosing the right seal, read the article: “Drop-Down Thresholds for Doors – How They Work and When to Use Them.”
Not sure which drop-down threshold to choose for your project? Contact us. We will help analyse the door construction, required parameters, and installation method, then select a solution suitable for the specific application.
If you would like to explore other threshold solutions, visit the Threshold Technology section. If you are looking for door or window hardware, discover our range of door hardware and window hardware solutions.
