DIY Deck Build - Advisable?

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143 posts

Master Geek

#2636268 15-Jan-2021 19:55

On the note of hole depth actually, doing a little research here now.

Placemakers says the feet 'concrete at the base' need to be 200 by 200 square and if you post is 300 in the ground, your hole needs to be 400 deep to allow 100mm of concrete underneath the post to do a proper footing.

Paul1977

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Uber Geek

#2636280 15-Jan-2021 20:51

I’ll probably just leave the hole depths as they are, it just means slightly longer posts required or a little more concrete - thinking about it some more I’m not sure it’s worth the time or effort to fill them in to try to save a few bucks.

For those who asked, I’m in Christchurch and I haven’t done an exact measurement for height yet but it is a fairly low deck (hence the need for more posts as I can’t use thicker bearers or joists as they’d make it too high). They’ll easily have more than 1/3 of the post below the ground - more like 2/3!

Bung

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#2636281 15-Jan-2021 20:57

WinNZ90:
Also going off stuff that Mitre10 and Bunnings says in their tutorials, I have found them to be very biased.

I read and watch their stuff but never just do it how they say, otherwise you spend more money than the professionals would

I find placemakers do better all around informationals and they don't force their stuff down your throats like the others do.

NO I DON'T WORK FOR PLACEMAKERS, NEVER HAVE NEVER WILL, I find them to be far to over priced

You are required to comply with the NZ Building Code not a tutorial put out by any supplier. The Placemakers guide is for a deck extending only 2m from the house so it avoids having to deal with any bracing. This means it doesn't cover the wider, deeper footings of a bracing or anchor pile. You can go straight to the NZS 3604 Light Timber Framed Building standard that covers the details as it is now a free download. From what I've seen of the Mitre10 guide it is better in covering the requirements with reference to the Standard. If you shop around for the hardware and aren't competing with every other Tom, Dick & Harry for timber in short supply at Xmas you can do a better job than " professionals" for less.

neb

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#2636289 15-Jan-2021 21:19

Paul1977:
For those who asked, I’m in Christchurch

And you're worried about the holes being too deep and stable? :-).

mdf

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#2636293 15-Jan-2021 21:31

Paul1977:

I’ll probably just leave the hole depths as they are, it just means slightly longer posts required or a little more concrete - thinking about it some more I’m not sure it’s worth the time or effort to fill them in to try to save a few bucks.

<snip>

If you're starting out and not able to do everything at once to hang your deck before concreting, I really like this type of pile foot/starter: http://www.space-it.nz/ (other brands are available). It makes sure you get enough concrete under the post and you can do individual posts/work at your own pace. Do the outside corners first and take care. Then you nail a long piece of scrap (or a joist) to these to make sure all the later posts line up. Try and get them reasonably plum, but for low posts like you're doing, nailing them to your joist will probably be enough to keep them plum. You won't need to worry about height since you can trim the tops off afterwards.

duckDecoy

194 posts

Master Geek

#2636298 15-Jan-2021 21:52

As many have stated here, don't be too driven by cost. If you've saved a few hundred dollars on [whatever] but it sinks and you have to tear it down and rebuild because its on a lean you'll be kicking yourself. A few hundred bucks across 20 years is nothing

WinNZ90

143 posts

Master Geek

#2636304 15-Jan-2021 21:55

Bung:
WinNZ90:

Also going off stuff that Mitre10 and Bunnings says in their tutorials, I have found them to be very biased.

I read and watch their stuff but never just do it how they say, otherwise you spend more money than the professionals would

I find placemakers do better all around informationals and they don't force their stuff down your throats like the others do.

NO I DON'T WORK FOR PLACEMAKERS, NEVER HAVE NEVER WILL, I find them to be far to over priced

You are required to comply with the NZ Building Code not a tutorial put out by any supplier. The Placemakers guide is for a deck extending only 2m from the house so it avoids having to deal with any bracing. This means it doesn't cover the wider, deeper footings of a bracing or anchor pile. You can go straight to the NZS 3604 Light Timber Framed Building standard that covers the details as it is now a free download. From what I've seen of the Mitre10 guide it is better in covering the requirements with reference to the Standard. If you shop around for the hardware and aren't competing with every other Tom, Dick & Harry for timber in short supply at Xmas you can do a better job than " professionals" for less.

Very true but they are a good place to get useful advice, however I don't know why I didn't think of this sooner tho, check out this mag:

https://www.buildmagazine.org.nz/assets/import-content/20140521/Build%20139%20Timber%20Decks%20Supplement.pdf

this mag covers everything you need to know

neb

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#2636306 15-Jan-2021 22:00

mdf:
If you're starting out and not able to do everything at once to hang your deck before concreting, I really like this type of pile foot/starter: http://www.space-it.nz/ (other brands are available).

+1 for those, or equivalents. The builders here used equivalents, it's the high-tech version of the usual "chuck a brick under it".

Paul1977

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#2636368 16-Jan-2021 09:23

WinNZ90:

Very true but they are a good place to get useful advice, however I don't know why I didn't think of this sooner tho, check out this mag:

https://www.buildmagazine.org.nz/assets/import-content/20140521/Build%20139%20Timber%20Decks%20Supplement.pdf

this mag covers everything you need to know

Thanks, that does have a lot of info and gives better context to the building code requirements so makes them easier to interpret.

WinNZ90

143 posts

Master Geek

#2636376 16-Jan-2021 09:50

I was just wondering, just how high in mm's is the deck going to be from the ground to the top of the decking once its all built. I was just thinking about what you wrote and how it is not going to be that high of the ground at all and was thinking anchor piles are going to have to be the ones you need to use for your deck, which means a 900mm deep hole.

So how low is it actually going to be? and all other dimension would be good too

tdgeek

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#2636404 16-Jan-2021 11:41

Paul1977:

I thought I'd read (possibly years ago) on Geekzone, that the easiest way to do the posts is to attached them to the bearers first and brace the whole thing in place, then concrete the holes.

Does that sound right, or am I misremembering?

I would definitely do that. Its all square. Pop the bearer length over the post holes, suspend as required to get it level, then concrete in, check and adjust straight after in case it was moved during concreting.

Paul1977

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#2636415 16-Jan-2021 12:04

WinNZ90:

I was just wondering, just how high in mm's is the deck going to be from the ground to the top of the decking once its all built. I was just thinking about what you wrote and how it is not going to be that high of the ground at all and was thinking anchor piles are going to have to be the ones you need to use for your deck, which means a 900mm deep hole.

So how low is it actually going to be? and all other dimension would be good too

Approx 340mm high, so yes, too low for braced piles. Deck will be approx 7500x4000 and piles will be at 1100mm centres.

Paul1977

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#2636416 16-Jan-2021 12:07

tdgeek:

Paul1977:

I thought I'd read (possibly years ago) on Geekzone, that the easiest way to do the posts is to attached them to the bearers first and brace the whole thing in place, then concrete the holes.

Does that sound right, or am I misremembering?

I would definitely do that. Its all square. Pop the bearer length over the post holes, suspend as required to get it level, then concrete in, check and adjust straight after in case it was moved during concreting.

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?

Paul1977

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#2636418 16-Jan-2021 12:08

On another note, thanks to everyone offering advice and encouragement. It's really fantastic.

tdgeek

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#2636473 16-Jan-2021 12:57

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?

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.

Another option is you have all the postholes dug. Assuming its level, you have the posts cut to size. Pop them in the holes and attach the bearer to each. Even if the first one is attached while the post and bearer are leaning, as long as the post is cut square attach it. It will be square. Lift the other end of the bearer on top of the last post, steady it temporarily and attach it. Attach the in-between posts and done.

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