Pre-formed, adjustable joists that provide a level sub structure ready to fix the decking of your choice

Proven cost efficacy. Definitely the fastest system to install, and one of the cheapest.

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TYPE A – Starting row of joists*
Place the first row of TYPE A joists against the wall or door entrance (the highest point of the slope). Keep a 12mm gap between the end of the joist and walls/doors. Using a sprit level placed on top, open the joist until it is level. Fix the joist together with 8g x 40 stainless wood screws at 200mm centres.

*For decks with less than a 100mm step down, use Type A-, available in 600mm lengths.


TYPE B – Second row of joists
Place the screw end of a TYPE B joist level with the end of the previous row, and put in first screw. Using a spirit level, open the joist until level and screw together as per row A. With row A and B now end for end, connect them together with the Stainless steel flitch plate, fixed horizontally with 8g x 40 stainless wood screws. (See figure below.)


TYPE C – Third row of joists
Repeat instructions as for TYPE B, connecting row B and C with the flitch plate fixed vertically  (see figure below). At any time a row can be cut to required length.


TYPE D – Fourth row of joists
Repeat instructions as for TYPE B, connecting row C and D with supplied stainless flitch, fixed vertically.

When installing on a 2 degree slope, you will need to place a 45 x 45mm runner under this row (rubber mounts attached). (See figure below.) Screw the joist to the runner with a 10g x 50 stainless steel screw.

1.5° to 2° Slope
The adjustable joists are designed to be used on sloping surfaces from 1.5 degrees to 2 degrees.

6 sizes available
Available in five 1200mm lengths: A, B, C, D, D+, and one 600mm length: A-. They are designed to connect together and allow for the increased height as the deck slopes away.

Observe Max Width
The maximum width of decking before extra runners are needed* is 3.6m  for a 2° slope and 4.8m for 1.5° degree slope. (See figure below.) *Extra runners supplied.


Cutting joists to fit
The width of the deck will determine the joist types needed. To shorten joist to the length of the deck, cut the joist and reposition the flitch. Cut joists should be primed and sealed with an exterior timber primer.

Width adjustment / lateral stability
At any time the last row of adjustable joists can be cut to measure. Once the width is complete the last row end can be supported with nogging to provide lateral stability (if required) prior to screwing the decking on.

Nogging and extra height runners
Adjustable Deckchair Joists are made from H3 treated LVL to reduce any timber warping. Nogging and extra height runners must also be H3 treated timber.

Drilling extra holes
Additional holes may need to be added to joists that have been cut to suit.

  • If required, drill 13mm holes 12mm deep.
  • Apply Holdfast Carbond 940 FC in and around each hole before inserting the nib of the joist mount.
  • Ensure the rows of joists do not exceed 450mm centres, regardless of the type of decking.

Extra Width
For extra width longer than 4.8m, purchase extra TYPE D joists and install by placing on 90mm high  x 45 mm wide runners. (Runners not supplied.)

End of Run
Decks will end over an internal gutter or flush at the end of the deck. (See Detail 1 and 2.) Stainless 50 x 50 Angle to be used in gutter support.


 DECK CHAIR joist mounts provide support and drainage to deck joists. Installing DECK CHAIR joist mounts in any way outside of the specifications below voids all warrantees and claims.





  • Easier to transport
  • Easier to set angle
  • More precise
  • No warping
  • Saves time


  • Requires transport of long lengths
  • Difficult to rip a straight line
  • Requires extra time ensuring lengths are cut to same angle
  • Prone to warping


The installation guide as a PDF version


Place an order for Adjustable Joists


Watch the animated installation process