How to build a freestanding deck?

boundxless

Hi guys,

Looking for some help with a deck frame.

Planning on doing a freestanding 3.2m x 4m deck to fill a spot in our yard. Single level frame. Can use 140x45 for all framing, but also happy to do 90x45 for joists. Whatever ends up cheaper.

Just trying to gather an understanding/draw up what’s actually needed for this - mainly how many posts will need to be done/where, how many bearers/joists as such will be needed, along with how far apart. Plan on a 400mm joist centre.

I have trouble planning and am a massive visual person – so having a drawn up one works well, but I can’t find a way to calculate it myself based off span tables.

The decking will be laid in the 3.2m length.

Previously built a 2.5x3m (halfway mark pictured below), was winging it and realised I went overkill on what was needed. Ended up having over 25 posts under it, noggins everywhere, etc. Every single joist/bearer had multiple posts and extra supports as I couldn’t understand spanning tables and again, am a visual learner/planner.

Thanks!

JacobZ

Hi @boundxless,

If you ended up with 25 posts underneath that deck, it would certainly be solid, but yes, it is way overkill.

I have written a few articles that I had hoped would clear up some of the confusion people have when designing decks. I think a lot of the confusion comes from a misunderstanding of what makes a bearer a bearer and a joist a joist, so How to understand deck components should hopefully help to clear this up. When you understand what the components are, it is much easier to understand the span tables. How to understand deck span tables should hopefully help you to understand the span tables better and put them into action.

Here's a design that will work with your dimensions that uses 140x45. It will give you a solid deck that is well within the limits of the bearer and joist span tables and will only use 12 posts total.

The bearers sit on posts that are spaced either 900mm or 950mm apart, which is well within the allowable 1400mm span for a 140x45 acting as a bearer.

The joists span approximately 1932mm between the bearers, which is well within the 2600mm allowable span when they are covering a single span.

Let me know what you think, and if there are any alterations required or if you'd like me to explain my reasoning behind anything, please let me know. 

I really enjoy designing decks and would love to help you understand them better if I can, so please don't hesitate to ask questions if you have any.

Jacob