How to attach joists to end rims for deck extension?

Hi,

I am extending my deck and planning to build a long bench on top of it. The bench will weigh roughly 500kg by the time I build the frame using 90 x 45 h3 and then completing it using composite decking boards on the face. The bench will be 4.4m long. I would appreciate some guidance on the flooring frame please. The frame is roughly 6.4m x 1.2. I have supported the rims using stirrups every 1.2m. I have joined the joists to the rim by using two bugle screws (100mm) on each end. The joists are roughly 450mm apart. Is it sufficient to have joists joined using the bugle or is it better to also add joists hangers please to give the structure the strength to support 500+ kgs. The boards on the frame are temporary to walk easily. Many thanks

Community manager's note: Check out How to build a low-level deck for expert advice.

.Existing deck extension

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Comments

Hello @tejmankar

Thank you for sharing your decking project with us. I'm afraid that using joist hangers will not be enough to support the weight of your table. On the condition that the table will be staying in one place, the area where the legs will be positioned must be reinforced to carry the weight of the table and the items that will be put on top of it.

I recommend reading this discussion - Low-level deck that needs to support tons of weight by @Adog. To summarize the recommendations made in the discussion. It's suggested that you double up the joists where the table will be sitting and space them so the legs can sit on the joists rather than the decking boards. It's also recommended to use pedestal feet directly under the legs. This is so that the weight of the table is on the ground and not on the decking frame.

Please keep us updated with your progress, we look forward to seeing your updated deck.

If you need further assistance, please let us know.

Eric

https://www.workshop.bunnings.com.au/discussion/comment/17316#Comment_17316

Thanks for the prompt reply @EricL ,

Essentially, I will be building a seat like this. Please have a look at the photos attached.

The load will be spread across the frame. I have included another photo with the boards removed where the frame of the seat will seat. I will but covering the seat the floor with boards after the fact. FYI, under the weed mat, there is soil. Looking forward to your suggestions

https://www.workshop.bunnings.com.au/discussion/comment/71266#Comment_71266

Hello @tejmankar

Thank you so much for posting the proposed structure you're putting on your deck. The question that comes to mind is, how much space do you have under your deck? I would still go with the original suggestion made earlier, but this time you'll need to find out if you can put a paver and pedestal feet underneath. As the weight is now spread out, I propose putting supports along the length of the footing of the structure. As I mentioned, it would be best if the weight is placed on the ground rather than the frame of the deck.

I suggest putting a Pedestal Foot every meter both at the front and back of the joist where the footing of the structure will be placed. I recommend using Brighton Masonry 300 x 300 x 40mm Charcoal Mypave Paver or similar to serve as a base for the pedestal.

If you need further assistance, please let us know.

Eric

https://www.workshop.bunnings.com.au/discussion/comment/98856#Comment_98856

Thanks for the response. Your suggestions make sense. There is soil under the weed mat so I can dig a little and even pour a little concrete (100mm) and then place the foot on top of it. I have attached another photo with markings on it. The red rectangle is where the bench will be placed roughly. The purple circles is where the stirrups are. If I understand correctly, you are recommending to insert the pedestal foot where I have got the green markings under the joist. Is this correct please? Also, would it be required to have double joists and double noggins if we put the inserts in? Another question is will the joist hangers give the joists additional strength. They are currently held by bugle screws (100mm) Thank you.

https://www.workshop.bunnings.com.au/discussion/comment/116210#Comment_116210

Hello @tejmankar

You've got the idea, my friend. However, I still recommend using the paver as waiting for the concrete to dry will take at least another week to hit full strength. But I leave the decision to you. Using bugle screws is fine adding the joist hangers adds extra strength. Adding extra joists will make your frame that much stronger. I tend to over-engineer things so I agree with your ideas. You can imagine the weight of the seat you are about to build plus the number of people who will be sitting there. It has to be strong to take all that weight.

If you need further assistance, please let us know.

Eric

https://www.workshop.bunnings.com.au/discussion/comment/126118#Comment_126118

Sorry, one more question please. Would you recommend putting some blue metal on the soil and then paver on top or the paver can go directly on the soil please?

Thanks,
Tej

https://www.workshop.bunnings.com.au/discussion/comment/132731#Comment_132731

Placing blue metal should be perfect. Make sure to tamp them into place so that the paver will not sink or settle. If you have any other questions about your project, please don't hesitate to post them. Our members are more than happy to provide you with advice and information.

If you need further assistance, please let us know.

Eric

https://www.workshop.bunnings.com.au/discussion/comment/136803#Comment_136803

I have had a stab at it. Please find some pictures attached. Does this look ok ? I might throw some concrete around the edges to hold it steady.

https://www.workshop.bunnings.com.au/discussion/comment/139591#Comment_139591

Very nicely done, but I suggest adding more blue steel to give yourself a good base for the paver. I recommend not removing the weed mat and placing the blue steel over the weed mat.

If you need further assistance, please let us know.

Eric

https://www.workshop.bunnings.com.au/discussion/comment/141493#Comment_141493

Thanks @EricL

I will give it a go later in the week and post some photos. Appreciate the guidance.

https://www.workshop.bunnings.com.au/discussion/comment/141493#Comment_141493

I have mixed cement with blue metal. I have then covered with weed mat and placed paver on top over some more blue metal. It feels sturdy now 🙂 thanks for the guidance. Please find some pictures attached.

https://www.workshop.bunnings.com.au/discussion/comment/142915#Comment_142915

That looks excellent, @tejmankar. Your added effort will ensure the longevity of the project.

Be sure to update us with some images when you're finished.

Mitchell

https://www.workshop.bunnings.com.au/discussion/comment/143907#Comment_143907

Thanks @MitchellMc

I am not sure if I need a separate topic for this question but I wanted to check about an existing deck which has 90 x 45 joists at 450mm distance. I wanted to know if it is generally stronger to have double joists or an additional joist between the two existing joists. i.e. joists at every 225mm.

Thoughts?

Wish you a happy new year

Regards,
Tej

https://www.workshop.bunnings.com.au/discussion/comment/144682#Comment_144682

What's the context surrounding your question? Is the deck bearing weight as was needed here? Whether you laminate two joists together or add one in between, it would add a similar amount of strength and any difference might be inconsequential. You're adding the same amount of timber to the structure either way.

The structure will bear a similar amount of weight either way, but the decking boards get supported better with and additional joists in between as they don't have to span as far. A 450mm spacing is more than adequate for a standard deck, though.

Happy New Year to you too!

Mitchell

https://www.workshop.bunnings.com.au/discussion/comment/145244#Comment_145244

Hi @MitchellMc ,

The work I have just done is to extend the existing deck. Please find attached the photos of the existing deck. The existing deck will also hold a bench in C shape and will be 3.2m long and 1.5m on the sides. Please find attached the design of the upgrade. My concern was to make sure that the deck can hold ~1000 kgs. as the bench it itself will weigh about 550kgs to 600kgs and the people sitting will add to it.. I wanted to make sure that the deck frame is very strong. Any thoughts? I have changed the design to move the bench on existing deck rather than what I just built (extension). The extension will now have the table in the new design and bench will move onto the existing deck. Looking forward to your comments.

https://www.workshop.bunnings.com.au/discussion/comment/145694#Comment_145694

That extra weight is being evenly distributed over the entire area @tejmankar. You don't need to worry about the weight of people. That's factored into standard deck construction. A deck can hold people and additional weight above what would be considered ordinary usage.

If you wanted to make the area really strong, you could add another two posts at the red stars for support and then run additional joists across, as previously mentioned. I don't see any point running additional joists unless you add the additional supports to the mid-bearer. That's the weak point.

Mitchell

https://www.workshop.bunnings.com.au/discussion/comment/146030#Comment_146030

Thanks @MitchellMc

I will also be adding blocks (noggins) every 450/500mm which currently do not exist. Do you see any point in adding joist hangers to the existing joists please? I will consider adding two additional posts before I decide to add joists.

Also, in terms of additional joists - The current width is 2700 with the bearer at the centre so the span is roughly 1350. Would it be ok if I add joist from one end (using joist hander) and rest it on the centre bearer do the same from the other end and then join them together in the centre using a piece of timber. Essentially they will be 1350mm (90x45) resting on the centre bearer and joined in the centre using an overlapping piece of timber. Reason for asking is I can't find 2700mm timber easily but I do have 2m lengths which I can use. Thoughts? 🙂

https://www.workshop.bunnings.com.au/discussion/comment/146322#Comment_146322

As long as the existing joists are sufficiently connected, I see no reason for adding additional joist hangers.

You could graft the two 1350mm joists together in the middle. However, they'll be far stronger in a single length. With your proposed method, the central bearer will be carrying the majority of the weight, whereas if the joists are of a singular length, they'll be bearing some of the weight.

Mitchell

https://www.workshop.bunnings.com.au/discussion/comment/146555#Comment_146555

Thanks @MitchellMc

I will wait for the timber to become available and continue. Will send some photos after

Regards,

Tej

https://www.workshop.bunnings.com.au/discussion/comment/146756#Comment_146756

I'm building a small deck myself at the moment and have also been held up by timber supply issues @tejmankar. I finally managed to source some joists the other day.

I can't wait to see your project finished. Keep us updated.

Mitchell

https://www.workshop.bunnings.com.au/discussion/comment/146911#Comment_146911

When I started digging to add the two additional posts, I found an ag line roughly 400mm from the surface where the first post should be located? What are my options here please? Will I need to reroute the agline or can I pour concrete over it ? Haven't dealt with aglines before 🙂

Also, where I dug for the second post I found that the storm water drain pipe is cracked. Is there a way to repair it please? Thanks.

Thanks,
Tej

https://www.workshop.bunnings.com.au/discussion/comment/147045#Comment_147045

You're very close to that stormwater pit as well @tejmankar. Probably not the best idea to place a footer directly above and agline.

I'm not sure why I didn't notice this earlier but is that bearer doubled up? What's the thickness? I presumed it was a single 45mm thick bearer spanning (approx) 1.8m(?) to the post, and that's why I advised additional posts in-between. If that bearer is two laminated timbers at 90mm thick, it's should be fine as is and the deck appears to be already over-engineered. I now don't feel a post is necessary where the drain is.

Mitchell

https://www.workshop.bunnings.com.au/discussion/comment/147150#Comment_147150

The bearer is doubled up 190 x 45 x 2. Please find photos attached with distances. I managed to dig out the ag line if a post is required and I have also dug up to repair the cracked pipe. You reckon the additional posts are not required please? Can I add the additional joists without the additional posts? Look forward to your thoughts? thanks.

https://www.workshop.bunnings.com.au/discussion/comment/147248#Comment_147248

Even a single 190 x 45mm would be adequate to span those distances @tejmankar. The two are more than capable. I don't believe other posts are necessary, even with the additional joists.

Mitchell

https://www.workshop.bunnings.com.au/discussion/comment/147332#Comment_147332

Hi again @MitchellMc ,

One more question. Since I have got all the material now and dug up everything, if I am wondering if I should just install them. I can move the ag line easily now. How far do I have to be from the storm water pit to install the post please?

Other option is to return everything back 🙂

Thanks,
Tej

https://www.workshop.bunnings.com.au/discussion/comment/147417#Comment_147417

Might as well install them now @tejmankar. If you can set the footer back 10cm from the pit that should be plenty.

Mitchell

https://www.workshop.bunnings.com.au/discussion/comment/147481#Comment_147481

Thanks @MitchellMc and in terms of distance from the storm water pipe, would that be 10cm as well please?

Regards,
Tej

https://www.workshop.bunnings.com.au/discussion/comment/147541#Comment_147541

Yes, @tejmankar. Just enough gap that they wouldn't touch each other with any movement. You could likely bring the pipe right next to the foundation; I just don't want it to settle and crush the pipe on you.

Mitchell

https://www.workshop.bunnings.com.au/discussion/comment/147591#Comment_147591

The posts are in. Please find some photos attached.

20220107_125405 C.jpg

20220107_125417 C.jpg

Post copy.jpg

https://www.workshop.bunnings.com.au/discussion/comment/147641#Comment_147641

Looking rock solid there @tejmankar! Sensational work.

Mitchell

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