Installation notice for adjustable lumber joist pedestal


  • Joists must be made of wood or aluminium Never install a composite wood joist
  • It is appropriate to anticipate a density of pedestals, such that the centre-to-centre distance does not exceed 60 cm in both directions, in compliance with DTU 51.4 (French exterior wood decking construction rules)


Step 1: Analyse your ground surface

  • Soft stabilised ground (grass, dirt…):
    • Excavate the ground
    • Use geotextile fabric (to prevent weed growth under your deck)
    • Cover with gravel to reach the desired height
  • SConcrete ground or stabilised plot (gravel, draining millrun): the pedestals are ready to be installed


Step 2: Calculate the height of pedestals

Height of NIVO® pedestal = height of finished work – height of work structure

X = H-(A+B)


Step 3: Install the pedestals

1.       Install the joist on pedestals, then, using a level, check the flatness of the installation (adjust the height of pedestals by turning the ring).


2.       Install as many pedestals as necessary under your joist, and adjust their height.


3.       Pre-drill the joist with a D=5 mm drill bit. Screw the joist into the pedestals from the top or the side, with a 6×90 mm or 6×120 mm bolt (depending on pedestal size)


Special situations :  :

–          Connection between 2 joists on a pedestal: screw to 27 mm maximum from the middle of the pedestal to avoid blocking the adjustment screw.


–          Length of joist greater than 3 m : It is advised to set the deck spacers in staggered rows to maintain joists in the axis and avoid warping. On both sides of the frame, double the joists to make finishing baseboards extending past the pedestal. This enables positioning of pedestals in low profile, and avoids having these extend above the deck. Joists must be attached at the end of the deck to another structural wooden part screwed with 6×120 mm screws (peripheral belt).


–          Skirting of the deck:  :

On the periphery of the frame

  • Screw, using 40 x 40 mm galvanised flat angle brackets, studs made of 60×80 mm structural wooden part trimmings.
  • Attach these studs under the frame.
  • Attach finishing baseboards (misaligned deck boards) to studs made of 60×80 mm structural wooden parts.

It is better to cover the ends of deck boards with the skirting .This prevents splits and cracks from being visible at the end of the deck board.