Post by: DannyG on August 14, 2018, 01:34:39 PM
Firstly the deck is on the ground.
I have attached a render of the area but its basically a 6m x 6m main deck with a little 5.4m x 2m extension.
My main question is that according to Aust Standards I need to use double bearers. Is this right? Its not over 1m off the gorund, it is on the ground or around 300mm above the ground.
I was going to use 140mm x 45mm bearers on 90mm x 90mm posts that will be concreted into the ground via post stirrups. Then use 90mm x 45mm joists, 450mm apart as per my flooring requirement. I have used the AS to work out the amount the spacing for the bearers and posts.
I have no problems using double bearers but it seems like an extra cost for a lot of overkill??
Any builders or others that have built decks care to enlighten me? Perhaps show some pics of your decks sub structure?? :)
Thanks for any help.
Post by: WilSurf on August 14, 2018, 02:15:42 PM
Will follow this.
Post by: GBC on August 15, 2018, 04:16:55 AM
Post by: Rumpig on August 15, 2018, 08:07:19 AM
Post by: #jonesy on August 15, 2018, 09:11:33 AM
I bolted up the bearers to the posts and propped them over the holes and poured the concrete. I found it easier to get the levels that way. If it is low enough you could even put your double bearers direct into the stirrup.
Post by: DannyG on August 15, 2018, 09:55:43 AM
Here is a link to the URL for the Australian Standards.
https://www.ozisuzu.com.au/files/85884.pdf (https://www.ozisuzu.com.au/files/85884.pdf)
And here is a link to a good resource for working out bearer spaces, post spaces and bearer/joist sizing. It looks complicated initially but when you read it, its actually quite simple to follow.
https://www.softwoods.com.au/blog/blog-diy/build-deck-step/ (https://www.softwoods.com.au/blog/blog-diy/build-deck-step/)
Post by: tryagain on August 15, 2018, 11:33:31 AM
Post by: #jonesy on August 15, 2018, 01:28:48 PM
In the spot they are way overkill which was a add-on, but further in and around the spans are bigger. It was easier to use them than sit down no go through all the calculations.
Try a few different scenarios to work out your cost. Bigger timbers mean bigger spans. That means less bearers, posts, holes etc.
I used to have a computer program that did all the calculations and work out the prices
Post by: DannyG on August 15, 2018, 01:31:01 PM
I took a pic of one of my bearers are actually 190x45 (x2)
In the spot they are way overkill which was a add-on, but further in and around the spans are bigger. It was easier to use them than sit down no go through all the calculations.
Try a few different scenarios to work out your cost. Bigger timbers mean bigger spans. That means less bearers, posts, holes etc.
I used to have a computer program that did all the calculations and work out the prices
Thanks, what do you have between the bearers and joists? Want me to send you my plans so you can figure out the most cost effective way to build my deck? :D
Post by: Marcus73 on August 15, 2018, 03:46:14 PM
Thanks, what do you have between the bearers and joists? Want me to send you my plans so you can figure out the most cost effective way to build my deck? :D
Geez not bad are ya?
Do you have a go fund me page too?
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Post by: DannyG on August 15, 2018, 04:12:45 PM
Geez not bad are ya?
Do you have a go fund me page too?
Sent from my iPhone using Tapatalk
No but I’ll happily take donations on patreon ;D
Post by: Moggy on August 15, 2018, 06:33:01 PM
Sent from my F8331 using Tapatalk
Post by: #jonesy on August 15, 2018, 09:19:37 PM
So 6 metres width
90 - 1000 bearer spacings. (7 bearers)
140 -2400 spacing (4 bearers)
190 - 3500 spacing (3 bearers)
So basically bigger joists will cost more, but you save on bearers and stirrups.
Then work out the same for bearers. Bigger beaters will mean less holes saving on stirrups and concrete.
It's a bit of fiddling but could save a few dollars.
.
Post by: DannyG on August 16, 2018, 10:11:40 AM
Hyne timbers used to have a program that would give you timber sizes, you simply entered the data. Try Googleing Hyne.com.au
Sent from my F8331 using Tapatalk
We only use Mac, they only have a PC option so I might pull out an old windows laptop and check it out, it looks interesting. Thanks.
Just sit down and work out the joists spans for 90, 140, 190 etc
So 6 metres width
90 - 1000 bearer spacings. (7 bearers)
140 -2400 spacing (4 bearers)
190 - 3500 spacing (3 bearers)
So basically bigger joists will cost more, but you save on bearers and stirrups.
Then work out the same for bearers. Bigger beaters will mean less holes saving on stirrups and concrete.
It's a bit of fiddling but could save a few dollars.
.
Thanks Jonesy Ill do some calculations and see what I come up with.
I am a little restricted for height and I dont want to have to excavate too much dirt to gain more space. But until the house is built I wont know for sure what I am left with.
Post by: GBC on August 16, 2018, 10:29:10 AM
Thanks for the replies.
Here is a link to the URL for the Australian Standards.
https://www.ozisuzu.com.au/files/85884.pdf (https://www.ozisuzu.com.au/files/85884.pdf)
And here is a link to a good resource for working out bearer spaces, post spaces and bearer/joist sizing. It looks complicated initially but when you read it, its actually quite simple to follow.
https://www.softwoods.com.au/blog/blog-diy/build-deck-step/ (https://www.softwoods.com.au/blog/blog-diy/build-deck-step/)
I just searched AS 1684 for any mention of compulsory double bearers and there isn't one. The only mention of double bearers is that they are allowed if you cannot source a single section large enough to do the job. I'd send a query to softwoods direct about that line because it sounds weird to me.
Your softwoods doc mentions that they only sell F7 pine for decking. If you are sourcing better graded timber you might be able to step back in section size and/or increase spacings.
What decking material are you using? What will it span?
What bearer spacing are you proposing to use?
Do you have a physical restraint height between the deck level and the ground?
Post by: DannyG on August 16, 2018, 10:49:25 AM
I just searched AS 1684 for any mention of compulsory double bearers and there isn't one. The only mention of double bearers is that they are allowed if you cannot source a single section large enough to do the job. I'd send a query to softwoods direct about that line because it sounds weird to me.
Your softwoods doc mentions that they only sell F7 pine for decking. If you are sourcing better graded timber you might be able to step back in section size and/or increase spacings.
What decking material are you using? What will it span?
What bearer spacing are you proposing to use?
Do you have a physical restraint height between the deck level and the ground?
You are correct. It does talk about double bearers to gain the required thickness if nescasary but in my case I believe I have the required thickness.
4.2.1.4 Double bearers (spaced bearers)
The required breadth of larger bearers may be obtained by using spaced double bearers.
Spacer blocks shall be placed between the bearers and, where relevant, at supports, at the
intervals specified in Table 4.1 (see Figure 4.3).
I think the AS changed in 2010 so perhaps double bearers was mandatory prior to the change, hence the document from softwoods?
I am undecided on the deck material yet but I think it will come down to either Ekodeck from Bunnings or another composite decking from these guys...http://www.ezywood.com.au/products.html (http://www.ezywood.com.au/products.html)
The bunnings one is solid and allows 450mm joist spans, the other one is hollow and requires 350mm joist spacings.
So far I am proposing to use 1.5m bearer spacing using 145x45 h7 treated pine and to have the posts also spaced 1.5m apart. But this is of course subject to change if I am advised otherwise.
The house is not yet build but it is a waffle slab so I am told Ill have around 300-400mm from the ground to where I want the decking to be with out too much excavation.
Post by: GBC on August 16, 2018, 10:59:08 AM
All of the span tables are derived from the old CSIRO handbook which was converted to metric by the Tradac guys - they are getting more complicated and saying less these days.
Post by: DannyG on August 16, 2018, 11:10:48 AM
Have you also thought about steel sub floor? There are plenty of wind up adjustable bearer/joist systems and probably reasonably priced. Its been a while since I did domestic stuff. I have put down a few plastic timber decks commercially. They expand and contract on the joints a bit so they don't reward craftsmanship. They look ok though and they are lasting well. Not cheap.
All of the span tables are derived from the old CSIRO handbook which was converted to metric by the Tradac guys - they are getting more complicated and saying less these days.
I have thought about steel, mainly because the house is being built on a steep hill so there was going to be an opportunity to hang the deck out over a 4m drop. The builder was going to incorporate the steel into the slab.
But as it turned out I was only willing to pay for one row of deep piers under the slab so the house is now set back a couple of metres away from the drop, so the deck is basically on the ground, albeit right at the edge of the drop off so thats why I have now gone back to wood thinking it would be cheaper.....but ill investigate steel.
You can sort of see the drop off here.
Post by: GBC on August 16, 2018, 11:18:01 AM
Got a local Stratco? Send them your rough plan with some dimensions and they will detail it and price it up (should).
Post by: #jonesy on August 16, 2018, 12:48:58 PM
I just searched AS 1684 for any mention of compulsory double bearers and there isn't one. The only mention of double bearers is that they are allowed if you cannot source a single section large enough to do the job. I'd send a query to softwoods direct about that line because it sounds weird to me.Supplement to AS1684 table 49. Specifies double bearers.
Your softwoods doc mentions that they only sell F7 pine for decking. If you are sourcing better graded timber you might be able to step back in section size and/or increase spacings.
What decking material are you using? What will it span?
What bearer spacing are you proposing to use?
Do you have a physical restraint height between the deck level and the ground?
https://www.scribd.com/doc/309660524/AS-1684-2-2010-Supplements-Non-Cyclonic# (https://www.scribd.com/doc/309660524/AS-1684-2-2010-Supplements-Non-Cyclonic#)
Post by: achjimmy on August 17, 2018, 11:32:55 AM
Post by: WilSurf on August 17, 2018, 01:26:33 PM
Just redoing my deck. Got the span tables from onesteel and all the bearers will be duragal . Proper RHS steel and span distances are good. Won’t rot (previous deck) won’t burn going to use rolled steel joists . Prices compared to timber are reasonable and every piece comes straight ;D
That's something for me to think about.
I want to install decking around our spa, on top of the pavers.
Post by: prodigyrf on August 20, 2018, 12:02:58 AM
Post by: prodigyrf on August 20, 2018, 12:33:01 AM
That's something for me to think about.
I want to install decking around our spa, on top of the pavers.
Did that for a client once and they wanted to keep it low so we used 50x50x1.6 square galv joists and a heap of window packers with construction adhesive for levelling and then wingteks for the decking with dampcourse between the galv and decking although you can use bituminous paint on the steel if you're not fussed about spillage.
https://www.ebay.com.au/itm/TRADEMARK-PACKERS-Mixed-40x75mm-500PK-WINDOW-PACKERS-SHIMS/223031818945 (https://www.ebay.com.au/itm/TRADEMARK-PACKERS-Mixed-40x75mm-500PK-WINDOW-PACKERS-SHIMS/223031818945)
https://www.buildex.com.au/products/steel-frame-housing/6-on-site/16-wing-teks/ (https://www.buildex.com.au/products/steel-frame-housing/6-on-site/16-wing-teks/)
Construction adhesive to the packers and pavers/concrete is just to hold the galv joists in place while you fix the decking as it's not going to move once it's all decked
Post by: Nomad on August 21, 2018, 10:24:27 PM
I currently have 2 x 245 x 45 (by 5 metre) treated timber bearers failing due to exposure to weather, I think they were holding water between them...
Had the engineer over, who wants some cash so is doing me a fee proposal to look at my whole house >:( >:( >:( >:(
Anyway my plans show that the builder had to options when he built, the above 2 x 245 x 45 in a treated pine or a 250 x 75 hardwood.
That may be where the double bearer come into your scenario.
I am simply replacing with a hardwood beam this time.
Post by: prodigyrf on August 27, 2018, 11:03:00 AM
and manufacturers like CCH give you the design tools at your fingertips- https://www.chhsoftware.com/designit-for-houses/ (https://www.chhsoftware.com/designit-for-houses/)
Horsey, here plenty water, horsey no drinky, horsey go thirsty :'(
Post by: GBC on August 27, 2018, 12:33:05 PM
Supplement to AS1684 table 49. Specifies double bearers.
https://www.scribd.com/doc/309660524/AS-1684-2-2010-Supplements-Non-Cyclonic# (https://www.scribd.com/doc/309660524/AS-1684-2-2010-Supplements-Non-Cyclonic#)
I didn't get a chance to get back to this. It look as though rather than being mandatory, they are specified for seasoned hardwoods. You can still use big section rhw, just probably less common these days so they have made allowances for laminating smaller seasoned sections as well. Happy to have someone with current experience give me a lesson here.
Timber QLD current doc attached still showing single and double bearer span tables.
http://www.google.com.au/url?sa=t&rct=j&q=&esrc=s&source=web&cd=9&ved=2ahUKEwjhlriOlYzdAhWFQd4KHTVUCA8QFjAIegQIAhAC&url=http%3A%2F%2Fwww.hyne.com.au%2Fdocuments%2FFeature%2520Documents%2FTQ_07_Timber-Deck_final.pdf&usg=AOvVaw2KzoVp2RnFNR4feLJj-l-R (http://www.google.com.au/url?sa=t&rct=j&q=&esrc=s&source=web&cd=9&ved=2ahUKEwjhlriOlYzdAhWFQd4KHTVUCA8QFjAIegQIAhAC&url=http%3A%2F%2Fwww.hyne.com.au%2Fdocuments%2FFeature%2520Documents%2FTQ_07_Timber-Deck_final.pdf&usg=AOvVaw2KzoVp2RnFNR4feLJj-l-R)
Post by: tryagain on September 11, 2018, 08:24:30 PM
I didn't get a chance to get back to this. It look as though rather than being mandatory, they are specified for seasoned hardwoods. You can still use big section rhw, just probably less common these days so they have made allowances for laminating smaller seasoned sections as well. Happy to have someone with current experience give me a lesson here.
Timber QLD current doc attached still showing single and double bearer span tables.
http://www.google.com.au/url?sa=t&rct=j&q=&esrc=s&source=web&cd=9&ved=2ahUKEwjhlriOlYzdAhWFQd4KHTVUCA8QFjAIegQIAhAC&url=http%3A%2F%2Fwww.hyne.com.au%2Fdocuments%2FFeature%2520Documents%2FTQ_07_Timber-Deck_final.pdf&usg=AOvVaw2KzoVp2RnFNR4feLJj-l-R (http://www.google.com.au/url?sa=t&rct=j&q=&esrc=s&source=web&cd=9&ved=2ahUKEwjhlriOlYzdAhWFQd4KHTVUCA8QFjAIegQIAhAC&url=http%3A%2F%2Fwww.hyne.com.au%2Fdocuments%2FFeature%2520Documents%2FTQ_07_Timber-Deck_final.pdf&usg=AOvVaw2KzoVp2RnFNR4feLJj-l-R)
What I suspect (haven't actually looked into it) is that the double bearers thing is a way of keeping everything simple/uniform. Basically at the ends, as there is only half of the tributaory area for the bearer, only half the strength is needed. So a way of keeping everything economical and simple, maintaining the same bearer size and spacing throughout is to just specify double bearers for all of the middle bearers.
Post by: prodigyrf on September 17, 2018, 02:18:49 AM
We've cut down the decent timber years ago so the stuff that's left is pretty ordinary now so it's plantation pine to keep up but better still for serious load bearing is engineered timber that is straight and true with no weak knots or shakes in it. It's guaranteed along every part of its length which you can't say about any natural cut timber but old habits die hard.
Post by: Fullberries on September 18, 2018, 05:36:06 PM
Look up g tape beat tape out there. Like a super masking tape that sticks to the joist so the water cant penetrate
Post by: Fullberries on September 18, 2018, 05:37:06 PM
Post by: #jonesy on September 18, 2018, 05:46:22 PM
this (https://www.bunnings.com.au/protectadeck-45mm-x-25m-pvc-joist_p0915409)
Post by: Rumpig on September 18, 2018, 06:54:36 PM
Post by: #jonesy on September 18, 2018, 08:56:32 PM
Post by: Rumpig on September 18, 2018, 09:53:27 PM
I think it stops it sitting on top of the joist. In my last 2 houses I've had to replace the rocks. The top of the joist between the decking boards was rotten. Under the decking boards were okay. The bearers were pretty much rotten on the entire top. Both were hardwood, Vic Ash or similar which isn't any good for outside. We don't have good hardwood in Victoria.yes it does supposedly protect them, but I do wonder how well really.....that is also why ripple deck was invented, allows airflow between the decking and joists to help dry them out and stop the rotting. As you say, Vic Ash is not suitable for doing such a job, we used it all the time for lintels inside house frames, but never outdoors.
Post by: Fullberries on September 19, 2018, 06:32:17 AM