Deck build - few questions

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33coupe

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#293345 14-Jan-2022 17:02

Hi there,

I'm having a deck built by a friend of a friend and I am a little unsure if it's being built correctly (half framing done) . I've tried looking online to see what's right etc but Im really not sure.
I was just wondering if someone were able to pm me and I can send some photos, or if someone was local and wouldn't mind a quick look over to put my mind at rest or raise some flags, would be really appreciated.
West Christchurch
Thanks

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Smpl Mnmlst
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#2850947 14-Jan-2022 17:34

Could you post some photos here with comments on things about which you’re dubious? If the sub-frame is only half done, it should be fairly easy to see how it’s being done - deck sub-frames are extremely simple in most cases. The important factors are timber treatment, timber cross-section dimensions and the spacing between the components.

These may help you:

https://www.onestopdeckshop.co.nz/piles-decking-timber/

https://www.google.com/search?as_q=Deck+sub+frame+construction+&as_epq=&as_oq=&as_eq=&as_nlo=&as_nhi=&lr=&cr=&as_qdr=all&as_sitesearch=Nz&as_occt=any&safe=images&as_filetype=&tbs=

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Jase2985

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#2850961 14-Jan-2022 18:34

Mitre 10 has a good video on the process. May or may not be the same as whats going on at your place but there is more than one way to skin a cat.

https://www.youtube.com/watch?v=4Sw6YJOcVWk

But as above post some pictures, they speak a thousand words

33coupe

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#2851092 15-Jan-2022 10:19

Thanks for the replies, apologies for the delay.

I'm not very good at putting pics on here, hopefully the link works.

https://photos.app.goo.gl/FigARaAQ6qQ2vZEp8

Some questions are

it has been nailed to the fence, when asked he said it was temporary
Seems quite high, I thought it would go under the door seal. He said there's still 10mm clearance

Thanks again

eracode

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#2851101 15-Jan-2022 11:40

Hmmm, where do we start? Overall IMO it looks pretty dodgy but it’s still a bit hard to tell from the photos.

The builder is a friend of a friend. What is his experience? Is he builder? Are you paying him for his work?

Are there piles concreted into the ground? - hard to see any in the photos. If there are piles, how many are there, how deep are they concreted in and what is the spacing between them?

What are the dimensions of the bearers? What is the spacing between the bearers? How are the bearers attached to the piles?

What are the dimensions of the timber being used for joists? In the photos, some look like they are 100x100, others look like 150x50 or 100x50 but it’s hard to tell.

What timber will be used for the decking itself? What will be the spacing between the joists?

As you say, the deck looks like it will be very high where it appears to adjoin the house.

I have many other questions and I really don’t want be alarmist or dramatic but I would be tempted to stop all this before it goes any further. I think you’re right to be concerned.

(Disclaimer: I am not a builder but I have built about 10 DIY decks over a 40-year period and I’m big-headed enough to think I understand the whole process very well - it’s not complicated).

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Edit: OP has added photos that now show piles and wider views/greater detail.

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Jase2985

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#2851103 15-Jan-2022 11:50

i am not a builder in any sense of the word but i don't think that looks like it will be strong enough.

Those bearers are tiny, like 100x50's, given the deck is quiet low to the ground and you can use 2x the width to give more strength, so 2x 100x50's to make a 100x100. sandwich them together and nail/screw.

Doesnt look to be any preservative on the tops of the piles to make them last longer.

The joist spacing looks to be too big too. and they look to be 75x50's joists.

Decks low to the ground are a challenge as its hard to get all the components into the space needed.

Personally wouldn't use black polythene under it either as it will pool water.

As eracode i would be pressing pause till you get someone to check it out.

If you can provide measurements of the timber etc it would help too.

FYI here is a picture of my deck framing.

125x125 piles, 90x90 bearers, and 90x45 joists, with composite decking on the top. Joist spacing is 400mm.

33coupe

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#2851110 15-Jan-2022 12:11

eracode:
Hmmm, where do we start? Overall IMO it looks pretty dodgy but it’s still a bit hard to tell from the photos.

The builder is a friend of a friend. What is his experience? Is he builder? Are you paying him for his work?

Are there piles concreted into ground? - hard to see any in the photos. If there are piles, how many are there, how deep are they concreted in and what is the spacing between them?

What is the spacing between the bearers? How are the bearers attached to the piles?

What are the dimensions of the timber being used for joists? In the photos, some look like they are 100x100, others look like 150x50 or 100x50 but it’s hard to tell.

What timber will be used for the decking itself? What will be the spacing between the joists?

As you say, the deck looks like it will be very high where it appears to adjoin the house.

I have many other questions and I really don’t want be alarmist or dramatic but I would be tempted to stop all this before it goes any further. I think you’re right to be concerned.

(Disclaimer: I am not a builder but I have built about 10 DIY decks over a 40-year period and I’m big-headed enough to think I understand the whole process very well).

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Thanks for the reply
From what we've been told and been shown photos he is a deck builder. Yes we are paying him, quite a lot less than other companies would charge (I know I know about buying/paying cheap, just thought being friend of friend doing cheaper cash job etc)

I'm not sure how many piles and how deep sorry, will count them and report back. Bearers are nailed to piles
From memory piles are 1300mm apart, bearers 1300 and 1600 apart (less distance at other end) with joists being 450mm apart

Bearers are 100x50, joists 70x50

Kwila to go on top

eracode

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#2851123 15-Jan-2022 13:12

It looks like you may have added photos that show the layout and piles more clearly.

The deck needs to conform with NZ Building Standard NZS3604. The standard does not contemplate 70x50 joists - that's very (too?) light for a joist. The smallest joist in the standard is 90x45 and the maximum joist span for those, when you have 450mm spacing between the joists, is 1.5m. With your smaller/lighter joist, the max span would be a lot less than 1.5m. This means that your bearer spacing of 1.6m is too wide - with 70x50 joists the deck will not be strong enough and will sag or spring when you walk on it.

I think you need deeper joists - but that's probably ruled out by the already too-high level of the deck. Alternatively you could add another line of bearers to put more support under the 70x50 joists.

I do not know but guessing that using 70x50 joists puts you outside the standard.

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wally22

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#2851147 15-Jan-2022 14:45

Others have raised their concerns and so will I. We will need more information about the dimensions of the deck. Then we can see if it anywhere near the building code. Note that I have always upped the spec from code for decks I have been part of, with agreement from the customers as the code is a minimum, assuming defect free timbers. From what I see from your photos you will have a very springy deck. I only saw what looked like 1 concrete pile? in the 2nd to last photo. The polythene is obscuring views of any piles. Kwila is only 19mm so needs close joists or it will flex.

Can you do a quick sketch of the plan showing dimensions and post it?

You should stop any further work until we have dimensions and work it out for you. 75x50 is doable if there is no other option, but you will need more of them and more joists and bearers, depending on overall dimensions of the deck.

Jase2985

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#2851148 15-Jan-2022 14:51

Man, those extra photos you have added just make it look even worse :(

what ever happened to evenly spacing things?

I dont think that deck will last very long without there being issues with it being springy, warping or getting all out of shape.

I would not be very happy with the work done thus far.

33coupe

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#2851158 15-Jan-2022 15:41

Thanks everyone. I've just been out there and done some measurements, have added the photo to the album, hopefully it can be read. If not please let me know.

I also tried treading on a piece of 30mm timber in between the bearers and you are right, slight spring/soft so not good! Will let them know to stop any more work, will need 2 more bearers.

eracode

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#2851176 15-Jan-2022 16:59

33coupe: Thanks everyone. I've just been out there and done some measurements, have added the photo to the album, hopefully it can be read. If not please let me know.

I also tried treading on a piece of 30mm timber in between the bearers and you are right, slight spring/soft so not good! Will let them know to stop any more work, will need 2 more bearers.

Sorry, don’t understand this - why 30mm?

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Clima

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#2851189 15-Jan-2022 17:51

Its about 20 years since I designed my son's deck. It had to comply with NZS3604 as it was on sloping ground and the front was about 2M above ground. I don't think compliance with NZS3604 is mandatory unless any part of the deck is 1m or more above ground - clearly yours is not. However it is a guide that should be followed if you want a secure surface that will not collapse under a close group of guests or bounce as you walk on it. All timbers within 150mm of the ground should be H4 - that looks like all your bearers.

The plastic underneath is probably not a good idea. In the photos it appears that it is holding puddles which will provide a damp atmosphere for the structure. The puddles will refill with every shower as the water drips through the decking.

eracode

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#2851191 15-Jan-2022 18:00

Clima:

I don't think compliance with NZS3604 is mandatory unless any part of the deck is 1m or more above ground …

FWIW, on their website, Mitre 10 say “Your deck must adhere to the NZS3604 Building Standard. This guide includes the relevant sections and tables you’ll need to design a standard deck that’s under 1m high and doesn’t require handrails. Work through these details step by step to design yours to standard.”

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tchart

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#2851268 15-Jan-2022 22:13

If you look at systems like nuraspike or tuffblock none of those would be compliant. Surely for a low deck like the one on the thread there is no danger of serious injury so it wouldn’t need to meet building standards?

https://www.onestopdeckshop.co.nz/wp-content/uploads/nurajack.jpg

Clima

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#2851274 15-Jan-2022 22:24

OOPS thank you. Yes all decks should meet requirements of NZS3604. Deck under 1.5M do not need consent.

The NZS3604:2011 is currently free to download. There is a link on this NZ Standards page

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