DIY Deck Build - Advisable?

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#2636585 16-Jan-2021 18:56

If you are using 125 x 125 square piles there should be no real problem cutting them to height. If you have enough length to play with have a few practice cuts above the final level to get your eye in.

tdgeek

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#2636590 16-Jan-2021 19:05

neb:
tdgeek:

Id do it in one piece. Joins will move no matter how they are done.You still need to lift the 7.5 bearer into place, adding a few short posts isnt a great deal more.

There is one consideration in favour of doing it in parts, bringing in and manhandling 7.5m bearers is going to be a bit of a job...

They have to be manhandled anyway. 7.5m isn't that long.

WinNZ90

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#2636600 16-Jan-2021 20:11

Paul1977:

When I was thinking about it last night, the issue is that the bearers will run the length of the deck which is about 7.5m. So could I use the same approach but in sections?

No you don't have to use the full length and 7.5 metre biggers might be hard to find as they are not a standard length from what I have read

https://www.buildmagazine.org.nz/assets/PDF/Build-162-28-Build-Right-Bearer-Joists.pdf?

The mag gives and example of how to do the joint

Paul1977

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#2636716 16-Jan-2021 22:13

WinNZ90:
No you don't have to use the full length and 7.5 metre biggers might be hard to find as they are not a standard length from what I have read

https://www.buildmagazine.org.nz/assets/PDF/Build-162-28-Build-Right-Bearer-Joists.pdf?

The mag gives and example of how to do the joint

But that example is only if I need a join over an anchor pile right (which I won’t have to). Over an ordinary pile can’t I just butt them end to end?

WinNZ90

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#2636738 17-Jan-2021 07:16

No no mate, its for over ordinary piles not anchor and braced piles

Bung

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#2636742 17-Jan-2021 08:00

@WinNZ90 the article that you brought to attention was "What can be done when joints are required in bearers over anchor or
braced piles?" written by a structural engineer. Whether you could rely on that if you had to submit your deck plans for Building Consent is another issue. You should be able to design a deck to avoid complication and stick with NZS3604. Fig 6:19 shows joint over ordinary pile.

WinNZ90

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#2636750 17-Jan-2021 09:18

Sorry about that last post, new baby syndrome lol

No joints over anchor and bracing piles are not a something that should be done but can be done if required as the article states.

Normally you do the joint over ordinary piles without the extra 1 metre bracing for the joint, at least that is how I was taught but I per to use the extra 1 metre to brace the joint whether it’s over a ordinary pile or a bracing pile just for extra measure, yes it adds a little extra timber cost but it’s worth it, especially since this deck is going to be in Christchurch, to have the extra structural soundness.

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wally22

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#2636926 17-Jan-2021 17:57

FYI

[url] https://www.stuff.co.nz/life-style/homed/garden/123971912/grooves-up-or-down-nzs-fierce-decking-debate-finally-settled [url]

neb

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#2636992 17-Jan-2021 19:04

wally22:
FYI

[url] https://www.stuff.co.nz/life-style/homed/garden/123971912/grooves-up-or-down-nzs-fierce-decking-debate-finally-settled [url]

Published 13:04, Jan 17 2021

OK, who's been reading this thread who knows a journalist?

In any case it's just quoting another guy, and the comment "many timber manufacturers actually specify the grooves to be put down, and some even void the warranty if the grooves side is up" is a specific point I've seen in other articles, without any backing evidence, so they could in turn be quoting source A, while source B would say the opposite. If it was that clear there'd be definitive statements in building requirements, guides, manufacturers instructions, etc.

Bung

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#2637061 17-Jan-2021 20:56

If the Stuff journalist had contacted a major timber mill rather than builder's crack it might have been a more "definitive " answer. Speaking of cracks, there is a paper on line "REDUCING THE SURFACE CHECKING OF DECK-BOARDS EXPOSED TO
NATURAL WEATHERING: EFFECTS OF WOOD SPECIES AND SURFACE PROFILING" Reeding is one way of reducing or hiding surface cracks known as checking on the surface of timber. It makes more sense than most of the other explanations that would be better achieved another way.

WinNZ90

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#2637069 17-Jan-2021 21:28

In any case it's just quoting another guy, and the comment "many timber manufacturers actually specify the grooves to be put down, and some even void the warranty if the grooves side is up" is a specific point I've seen in other articles, without any backing evidence, so they could in turn be quoting source A, while source B would say the opposite. If it was that clear there'd be definitive statements in building requirements, guides, manufacturers instructions, etc.

I saw your post and I thought to myself, I wonder if there is any standards requirements for grooved timber and low and behold there are

'Timber decking is typically grooved on one face and smooth on the other. Uncoated, profiled timber has a slip resistance of 0.45–0.6 at 90° to grooves so it meets the requirements of clause D1, while smooth timber only has a slip resistance of 0.2–0.35'

This article is about slatted decking but it has the above paragraph in it.

https://www.buildmagazine.org.nz/assets/PDF/Build-136-28-Build-Right-Slatted-decking.pdf?

Paul1977

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#2637442 18-Jan-2021 15:23

Below is a plan of the deck. It's next to the house but not attached, so freestanding. The bearers will be cantilevered a little over the posts, and joists will be cantilevered over the bearers.

Currently holes are all dug to depth for ordinary piles (expect one where I ran into a shallow stormwater from a nearby downpipe at approx 200mm). Any holes that need to be anchor piles I can dig out more.

Does my proposed placement of the anchor piles look correct? I believe it's right from how I'm reading of NZS3604, but would be great of someone more experienced could take a look.

As long as the 200mm hole over the storm water is in good solid ground, I think that would be compliant depthwise - but can I concrete essentially directly on top of the pipe? If not, what other options do I have to get around this?

Thanks

Click to enlarge:

wally22

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#2637453 18-Jan-2021 15:40

I would bridge over the shallow storm water pipe by placing piles on either side. I would not concrete over the pipe and add weight to it.

Note that is what I have done in the past with a similar situation.

1 more pile and 2 more holes to dig.

Paul1977

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#2637458 18-Jan-2021 15:52

wally22:

I would bridge over the shallow storm water pipe by placing piles on either side. I would not concrete over the pipe and add weight to it.

Note that is what I have done in the past with a similar situation.

1 more pile and 2 more holes to dig.

Didn't draw it on there, but the pipe is running almost horizontally when looking at that plan, so not sure I'll be able to get one on either side along the same bearer line.

wally22

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#2637485 18-Jan-2021 16:56

OK.

Make a bridge at right angles to the pipe that the bearer can rest on. If the horizontal piece of the bridge ends up below ground at all, use a pile(H5) for it.

Earlier you mentioned cutting piles. Always paint the cut ends with Metalex Concentrated Timber Preservative using appropriate safety precautions.

Alternatively and preferably, don't cut any piles. Some builders will happily cut piles and not treat the cut ends. The treatment is an envelope system so any break in the outside of the envelope should be retreated, but will not necessarily be as effective as the original commercial pressure treatment.

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