Installing Plastic Or Timber Joists & Posts On Soft Foundations

When installing plastic or timber joists & posts ensure the area is clear and free of any obstacles including any cables and pipes1. Measure and mark out the area including where holes need to be dug for posts ensuring posts are spaced every 1200mm approx. If newel posts are used, ensure the holes are dug in the right place

2. Dig 600mm minimum holes into the ground making sure the width of the hole is at least 4 times the width of the post

3. Measure and cut posts to the required height. Posts can be left longer and cut down at the end if preferred

4. Place a layer of gravel into each post hole to help hold the posts in place while the levels are checked

5. Pour concrete into the holes and wait to set

6. We advise using a weed membrane to stop any vegetation growing. Roll the membrane out over the area and cut to size. Gravel or pegs can be used to hold in place

7. Check all dimensions including outer board dimensions allowing any space for Newel Posts where required

Measure and mark the height of the deck taking into account deck boards. We advise creating a decline of 1% – 1.5% away from a property acting as a drainage slope

1. Measure and cut outer joists where required and clamp into place where marked. Pre-drill holes and screw together using 2 coach screws at each post

2. Measure and cut support beams where required for underneath the outer joists. Pre-drill holes and screw together using 2 coach screws at each post

3. Measure and cut inner joists where required. Pre-drill holes and screw together through the outer joists at each end at 300mm max intervals (centre to centre) using 2 coach screws. Add extra support by screwing through the inner joists and into the supporting beams

4. Leave a 10mm expansion gap between joist butt joins

5. Double joist where deck boards meet at butt joins allowing a 3mm gap between joists

* If newel posts are used measure and cut where required. Pre-drill holes and screw together using 2 coach screws through the outer joist and into each post. Ensure the posts are flush with the bottom of the outer joist. If numerous newel posts are used we recommend evenly spacing allowing access to the deck