Are my bearer and joist spans correct for large deck?

[Scottydont85]

Hi All

With the weather warming up, I'm getting ready to embark on my large outdoor deck. Hoping to have it finished ready for Christmas.

Just want to get some advise on my proposed stump/bearer and joist spans. Pretty confident in building the deck as Ive done a couple of years supervising a small tiny home company. Just was hoping to get an experts opinion to confirm my spans are correct. (pictured below)

NOTE: The top of the plan is where the deck will be connected to the house with a wailing plate. (hence the cantilever)

Thinking of using the following materials

135 x 19mm spotted gum decking

90 x 45mm treated pine joists

140 x 45mm double bearer

90 x 90mm treated pine posts

galvanised stirrups/high wind anchors

[Akanksha]

A warm welcome to the Bunnings Workshop community, @Scottydont85. We're delighted to have you join us. 

You obviously have plenty of knowledge and experience to share with the community so we are looking forward to seeing more of your posts soon. Please let me know if you ever need a hand getting the most from the site. We're here to help.

I'm sure our resident Bunnings D.I.Y. expert @EricL will be able to review your plans when he's back online later today. I'm also tagging experienced renovators @Adam_W, @ProjectPete, @diy_hausdesigns and @redbournreno for their thoughts in the meantime. 

Please do keep us updated as your deck project progresses. We'd love to see details and photos of your process. 

Akanksha

[EricL]

Hello @Scottydont85 

Allow me to welcome you as well to the Bunnings Workshop community. It's wonderful to have you join us, and thanks for sharing your question about your decking frame.

It looks very well laid out and the double bearer are sure to provide excellent support. I often over engineer my projects and usually have my posts only one meter apart. But I suppose it depends on how high this deck will be. Is it a low-level deck or will it be very high? Do you expect the deck to be conservatively occupied at one point? Will a lot of people be standing on it during a party? If you expect a crowd, I recommend reducing the space between bearers to one meter as well.

Let me call on our experienced members @Dave-1, @homeinmelbourne and @Adam_W for their recommendations.

If you need further assistance, please let us know.

Eric

[Dave-1]

Good Morning @Scottydont85 

Thats a nice layout of your deck. 

The post spacing I would reduce the distance between them

I like @EricL 's suggestion of  the 1250mm down to 1000mm between bearers.

I used the same type of stirrups and from memory had to chisel 10mm off my post bottoms. I also left the timber 10mm above the bottom of the U plate so the post would never sit in water.

Only other bit of advice I could say to look into is apparently there is a recomendation of some kind of weather strip? that is placed betwwen the joists and the timbers of the deck itself to help stop decay? Not sure if this is right but someone in here mught know.

I over enginerered my deck (built it from recyled hardwood) acording to my carpenter mate lol Thing is its still standing 11 years after I started building it. I need to do a tiny bit of maintance on it (couple of boards feel a little bouncy and the timber has weathered) but I think over engineering has prolonged its life. (I do intend to post the project, just havnt got there yet)

Cant wait to see the deck being built and that is a tight timeframe at the speed i work!

Dave

[Scottydont85]

Thanks @Dave-1 I think you and @EricL are right. I will probably reduce my bearer spacing to a metre. I like the though of it being over engineered. I want it to last a long time.

I am looking into the joist tape to protect the joist from rotting.. its a great idea and seems like a simple step to add longevity to it.

Scott

[EricL]

Hi @Scottydont85 

If you're looking for even more protection, I suggest painting the bottom and sides of the frame with Gripset Betta 1L Waterproofing Membrane Bitumen Rubber.

Please keep us updated with your progress, we look forward to seeing the start of your decking assembly.

Eric

[Scottydont85]

Hey @EricL  @Dave-1, @homeinmelbourne and @Adam_W    If I reduced the spacing of the posts to 1250mm and the Bearer span to 1000mm do you think I would still need to double the bearers? Or could I get away with just 1 140 x 45mm Bearer? (Image below)

[Dave-1]

Morning @Scottydont85

Thinking about your question, When you say "double the bearers" are you meaning side by side or two very close to each other?

Id go for a single bearer. I dont think there would be any bounce with the berares and spans you mention.

Hoping to see the pics of the project by Christmas

Dave

[EricL]

Hi @Scottydont85 

I would suggest reducing the space between posts even further down from 1250mm to 1000mm. This will provide you with very secure footing and should be possible for you to use a single bearer.

Eric

[Scottydont85]

Thanks @EricL and @Dave-1 Yes, I meant two laminated 140 x 45 timbers to create the thicker bearer.

But yes, I will reduce the posts to 1000mm and just go for the single bearer.

Hoping to start this weekend, but I imagine its going to take a few weekends over the coming months.