I'm hoping to embark on a decking project, but there are some challenges. I've attached some photos of the site, a diagram of posts, bearers and joists I found elsewhere and a rough drawing of the planned deck. At its front edge away from the building it will be almost at ground level. I found some good information on here but my issues are as follows:
The ground under the deck does not slope away, would it be ok to build a deck on this ground as long as the concrete footings are proud of ground level and don't allow water to gather?
I'd prefer to run bearers along the long axis and joists coming out perpendicular to the building, allowing me to run the decking lengthways across the front of the building, would this be an issue?
There are pipes running down the side of the building which would interfere with a one piece ledger board, how do I remedy this?
With regard to stairs to climb from the lower ground level to deck level, how are these created, mounted and attached to the deck/secured to the ground?
I can put in concrete footings and mount stirrups no worries, but do bearers have to be attached on top of posts or can they be bolted to the side of posts? If only to be mounted on top how do I make sure all my posts finish level?
I'm sure I have more questions but these are just the ones that immediately supporting to mind
Welcome to the Bunnings Worskhop community. It's fabulous to have you join us, and thank you for sharing your questions about building a deck.
It's great that you've found some useful information about deck building in the community. To keep your deck safe from water accumulation underneath, I suggest installing at least two french drains running parallel and equally spaced to provide adequate drainage for the area. Should you encounter very strong rain the french drains you've installed will protect your deck from getting water trapped underneath.
There are no issues with your plan on the framing layout, however, I would recommend drawing your own plan so that you'll be very familiar with the distance of the footings. Please keep in mind that the timber framing you'll be using will determine the distance you can place your footing.
Having pipes running along the wall means that you'll have to modify your deck framing and possibly add extra footing to support this part of the deck. Extra noggins and an independent free-floating frame are some of the things you'll have to consider when going around your pipes.
The good news is that you can purchase stair stringers that are pre-made saving you from having to make them. You'll need to build a cement base at the bottom of the deck for the stringer to be anchored on. As to the mounting of the bearers, you can do either one, in order to level the posts, I suggest using a builders line to mark each post.
Bunnings also has a seven-part series on how to build a deck:
Here are some handy links:
If you have any other questions we can help with, please let us know.
Thank you so much Eric for the detailed reply. As I thought it has generated more questions.
Should the French drains run across the slope, one about half way and one at the bottom? I do have a 2 cubic metre rubble drain nearby for stormwater from this building and a nearby shed.
Do decking boards come longer than 6m or will I have to have joins (staggered) on a deck section longer than 6m? Or would you recommend running the decking boards the other way to prevent butt joins?
No doubt there will be more questions along the way.
I suggest putting the french drain in parallel to the length of your deck pointed toward your rubble drain if possible. I'm afraid 5.7 meters is the longest length you can get in Merbau or composite decking.
As to decking panel orientation, it all depends on your preference regarding which way the boards face. If you wish to have a uniform look, I suggest using a picture frame layout with breaker boards. You can then calculate the lengths you'll need without having any butt joins.
If you need more advice or information, please let us know.
I've found 6m decking boards:
Now I'm thinking I'll run the stairs off the short edge of the deck so the deck space will end up 6m x 3m or so, plus stairs and I can run the 6m boards lengthwise.
I've put some pegs in which gives me a better idea of the fall under the deck. The deck finished height is roughly the underside surface of the board in the photos. The shortest peg is 370mm so I've got plenty of room for concrete footings, stirrups and varying length posts, with 120x45mm for bearers and 90x45mm for joists, plus 19mm decking.
With the height of the deck I can probably also do some minor earthworks so that ground falls away from the deck, which will be covered anyway so the ground under the deck won't receive any direct rainfall through the deck.
With the bearer and joist sizes mentioned how far apart should the joists be at a maximum (i.e. what's the minimum number of joists I could get away with)?
Also does anyone have a ballpark figure of the difference in price per square metre between treated pine and merbau decking? This deck is 18 square metres.
It's great that you've found some 6-meter length decking boards. I suggest having a look at the Hyne Span Table, it should give you a very good idea of how far the bearers and joists should be. I also suggest having a look at this discussion - Low-level composite deck over concrete slab by @Nat2. It's a very good example of a single-level deck frame with uneven mounting to the house.
Pine decking at 6-meters is currently priced at $23.88 and the per linear cost of Merbau is $6.60, when multiplied by 6-meters gives you a value of $39.60. Merbau decking is pre-oiled and should be something you should take into consideration. It is also classified as hardwood and technically will last longer than the pine decking panel.
Doing a bit of earthworks is always a plus and will prevent the bottom of your deck from getting water logged.
Please keep us updated with your progress, we look forward to seeing the start of your decking project.
Is this the right sort of timber I'm looking for in bearers and joists?
120 x 45mm Framing MGP10 H2 Blue Pine
I suggest using H3-treated timber instead. While H2 is treated, it is used for indoor framing. Whereas H3 is treated not only for insect attacks but against the weather as well.
I have another question that's probably easily answered about fixings.
Fixing the posts to the anchors/stirrups and fixing the anchors/stirrups into concrete I know about, but if the bearers sit on top of the posts, and the joists on top of the bearers how are these all fixed together?
The parts you mentioned are actually fixed to one another, there are several methods on how to join them together. But before we go any further, I suggest looking at the rules and regulations of your local council on building a deck. There possibly will be preferred methods and fixings that they require.
However, I suggest having a look at parts four and five of the Bunnings building a deck series that shows how the bearer is attached to the post and the joist attached to the bearer.
Bunnings build a deck series parts four and five:
If you need further assistance, please let us know.