Decking joist spacing?

darkwarrior

I'm trying to build a small deck as a DIY project. I was following a plan in a book but realized that it isn't incredibly specific in all the stages for things like joists and support beams. It has diagrams but no measurements.

The bulk of the frame is made from 76x48mm wood and support beams that are 75x75mm.

It's 2.4x2.4m, has a 2.4m central joist with two centre cross joists and a 75mmx75mm support block at each intersection. I'm not looking at adding the extra joists and the legs but this is where the guide kind of falls apart for me as reading/viewing other guides seems to suggest that only using corner supports will leave it spongy in the middle. And the amount of joist spacing also seems to differ.

Does anyone know based on these measurements what kind of spacing I need to be looking at? The guide says every 400mm which would mean 4 additional joists on each side of the deck. I'm also considering replacing the 75mm support blocks with additional legs. Necessary or no?

27col

Nip into Wickes and pick up their decking leaflet.

muckybutt

Alternatively .... http://www.richardburbidge.com/media/50788/outdoor-building-your-deck-fact-sheet.pdf

BoxerfanUK

I built a smallish deck (approx 10 sqm) in a corner of my garden but used 5" x 2" deck joists. 4" x 2" would have also done the job but I wanted to ensure it was really sturdy.

I constructed the complete frame in the middle of my garden and then when complete moved it (with some help) into position. It is supported by 4" x 4" posts concreted fairly shallow into the ground and coach bolts attach the frame to the support posts. I dug the holes, cut the posts to size, bolted the coach bolts through and then concreted using ready mixed postcrete from Wickes. It is as sturdy as anything and doesn't bend or flex at all even with half a dozen or more people on it. In terms of how many support posts I used, I just estimated where I needed the supports when the frame was in place.

Hope this helps