Hold-down roof dowels

Application of hold-down roof dowels in flat roof heat insulation systems

Flat roof composes of bearing and roofing structures is the most demanding building structure  capable of  withstanding various extreme loads for the long time:

  • External climatic, including various corrosion stresses
  • Internal micro-climate effects 
  • internal processes of aging  of roofing materials influence their mechanical properties 

When attaching insulation layer toflat roofing, mechanical fastening is used, ensuring spring (telescoric) effect during operation, which makes it possible to avoid mechanical demages of insulation and the fastener under the effect of vertical loads.
The fastener is a combination of hold-down plasic dowel and self-tappig screw, the design of which is defined by the relevant construction basic.
This type of fastening is used  for roof slopes under 10%.

  • Waterproofing layer
  • Thermal insulation layer 
  • Hold-down roof dowel 
  • Steam insulation film
  • Profiled sheet


Hold-down roof dowels are used for fastening of heat insulation materials and products of the waterproofing layer (PVC membrane) on flat roof to construction bases made of concrete, expanded clay layer  of roof pitch, metal profile, or wood.
Hpld-down roof dowels are produced in the Republic of Belarus under EKT brand in accordance with technical requirements TS BY 191235914.005-2014, in accordance with TR 2009/013/BY "Buildings and Structures, Construction Material and Products. Safety." This type of fastening has passed the procedure for assessment of usability and verification of complinance. 

Design options



For fastening of thermal insulation materials and products to flat roof

Hold-down roof dowel

DK-U (with pins)
For fastening of PVC membrane or water insulation of flt roof. *Most effective in combination with single membrane.

4,8х pointed, ceramic coating, TORX25
For direct fastening into wood metal profile up to 0,9 mm.
Or for indirect fastening into expanded clay concrete  using dowel  8х60 Type К.


4,8х bit, ceramic coating, TORX25
for fastening into metal profile, thickness 0,9 - 2,0 mm.

6,1х double thread, ceramic coating, TORX25
For direct installation in concrete into pre-driller hole with diameter of 5,0 mm

Technical parameters

Lenght of the GOK hold-down roof dowel is calculated according to the formula;
Where G is the thickness of the  insulation layer
L=15...25 mm is the gap between the dowel and the base required to ensure flexibility of the fastening joint (telescopic effect)

Calculation of the required length of the self-tapping  screw in accordance  with the expression;
where H=13mm is the  part of the  self-tapping screw located  in the hold-down roof  dowel.

*self-tappng screws with the next largest Ls nenght is selected

The required self-tapping screw is selected in accordance with the list of self-tapping screws presented in the table:

Regulatory requirements

Fastening elements used in roof thermal insulation systems are regulated by the requirements of TR 2009/013/BY "Buidings and srtuctures, consrtction materials and products. Safety. "Fulfillment of the requirements contained  in this key source demands receipt of the technical certificate and the declaration of conformity.

EKT Company LLC provides technical certiificates and declarations of conformity for all fasteners to which the requirements of this technical regulation apply.

In accordance with TCoCp 45-5.08-277-2013, slab insulation of rigid mineral wool slabs and waterproofing membrane must bt fastened by self-tapping screws according to rated loads as per SNiP 2.01.07, but in any case not less than one gfastener per each insulation sheet, based on the rated tear-off strenght of at least 0,5 kN per1m2 of roof and with a spancing of 200mm when fastening along the waterproofing membrane. The number of fastening elements must be increased 2 times at roof section with a width of 1.5 m along drop aprons, averhangs. abutting joints, edge and corner zones.

LLC "EKT Company"
Minsk, Belarus