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ACO façade channels for barrier-free thresholds

Successful installation of floor-level thresholds

Product certificates cannot replace the following three essential requirements for the successful installation of barrier-free thresholds:

  • Advice in the planning phase
  • Calculation of the drainage capacity
  • Practical experience

ACO supports you in all of these points.

Barrier-free entrance doors

In public buildings, barrier-free entrance doors are always provided.

The transition from living areas to roof terraces, balconies or loggias, which should be as level as possible, as well as the stepless building entrance area are critical construction points that must be carefully detailed, as moisture damage can occur very quickly due to weather influences (driving rain, snowbag formation). Already in the early planning phase, all boundary conditions should be taken into account, e.g. interior and exterior construction thicknesses, ceiling offset and slope.

The barrier-free transition from buildings to the outdoors often leads to conflicts with technical regulations. There are tried and tested solutions for this, but they do not conform to all points of the directive: By laying external drainage channels parallel to the door, protection against moisture can be fulfilled without a major difference in height between the external and internal levels.

The demand not only contradict the formulated requirements for barrier-free construction, but were and are equally regarded as impractical by numerous architects, property managers and flat users. Large threshold heights are undesirable in many circles and are not implemented.

Planning barrier-free door thresholds

All experience gained in reducing the connection height from 15 cm to 5 cm should be used. Procedure for planning barrier-free door thresholds:

Key points to be considered in the preliminary planning:

  • Height planning of the shell
  • Interior and exterior thicknesses
  • Consider thermal insulation
  • Design of the slope

General information on threshold construction:

  • It is a special construction that must be specified by the planning.
  • A drainage channel is mandatory in this area
  • The consent of the building owner is required for this connection detail
  • Coordination between planner and executor is required

Barrier-free threshold: Check list for planning

Evaluation of a planned threshold formation:

  • Hydraulic calculation of a drainage channel must be available
  • Existence of a roof, a closed parapet or lateral weather protection can be supportive
  • Check and observe alignment and main wind direction

Evaluation of the surface drainage:

  • An elevated surface covering with min. 3 cm free space for horizontal drainage is recommended here.
  • Supporting the gravel or chippings layer with drainage mats or spur channels already brings a clear improvement here.
  • Drainage layers consisting only of chippings or gravel have the lowest drainage performance and are most unsafe due to contamination


  • A planned slope of at least 2% of all water-bearing layers.
  • Slope in any case away from the connection point


  • The waterproofing height should be at least up to the upper edge of the gutter system.
  • The waterproofing must be secured to prevent it from running behind the gutter.
  • On-site storage of the waterproofing

Roof drains:

  • At least 2 drainage points are to be provided
  • An emergency overflow can be used as a second drainage point

Drainage channel:

  • Dimensioning according to hydraulic calculation taking into account all boundary conditions.
  • Laying across the entire width at right angles to the direction of travel
  • Maximum distance to the waterproofing connection 5 cm
  • Use of channel bodies perforated on both sides


  • Use of mesh gratings (mesh 30x10, the longer mesh size across the direction of travel).
  • More than 50% free opening cross-section
  • Minimum slot width of 8 mm
  • A dirt fleece underneath the grating is not advisable under any circumstances; the whole system loses its function if the mesh becomes clogged.

Barrier-free lower door stops and thresholds:

  • The tightness of lower door stops can be achieved by using special rubber profile seals or magnetic door seals.
  • The seal must be secured against running behind the door profile.
  • The sealing height incl. door profile should be at least up to the upper edge of the gutter system.
  • Maximum height 2cm


  • The lost connection height of the waterproofing is restored by an ACO façade and terrace channel correctly dimensioned in the preliminary planning
  • Taking into account all the listed boundary conditions, a barrier-free threshold can also be implemented at the same level

Source reference

Essential contents have been taken from the book "Schäden an Balonen" (Damage to Balconies) in cooperation with and with the kind permission of the author
Dipl.-Ing. Nils Oster, Ö.B.U.V. expert, the book "Schäden an Balonen" ("Damage to Balconies")
from the series "Schadenfreies Bauen" of the Frauenhofer IRB Verlag.