Need help with deck substructure plan

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coursefindernz

6 posts

Wannabe Geek

CourseFinder

#280432 14-Dec-2020 22:35

Hi All,

I am planning to build an L shaped LOW LEVEL deck (290mm above ground) next to a house with concrete foundation and I will be using joist hangers as I do not have sufficient ground clearance. I got the deck plan and started planning the framing but stuck with questions regarding the bearers overhang and pile positions next to the foundation. Could someone please help with the details.

Attached is an image of deck dimensions, timber details etc.

The questions I have are:

1. One end of the bearers will be towards the foundation. How close can I place a place next to foundation and how much can I overhang the bearer ?
2. At the end of bearers, can I place the joists between bearers using angle brackets or concerealed face fix joist hangers ?

Please let me know if any further details are needed. Appreciate your help with the queries

Thank you

Krish

Clima

130 posts

Master Geek
+1 received by user: 38

Lifetime subscriber

#2621570 15-Dec-2020 00:03

Your deck details were not attached. Bearers can cantilever up to 300mm. It's a tight design at 290mm. Timber less than 150mm from ground should be H4.

coursefindernz

6 posts

Wannabe Geek

CourseFinder

#2621632 15-Dec-2020 07:19

Here are the deck details (rough sketch of the frame, please ignore the piles not aligning in picture :-))

coursefindernz

6 posts

Wannabe Geek

CourseFinder

#2621633 15-Dec-2020 07:22

Deck plan top view

Ruphus

469 posts

Ultimate Geek
+1 received by user: 181

#2621654 15-Dec-2020 08:14

Download and have a read of NZS3604:2011, section 6, table 6.4. With the current pile placements, you'll need to review the bearer size as it appears to be under spec'd. If you add more piles so the max span of the bearer is 1.3m and the loaded dimension is under 1.2, then you'll be able to use 100x100mm for the bearers giving you more height to play with.

As the bearer spacing are closer, you'll then be able to adjust your joist size accordingly.

Paul1977

5171 posts

Uber Geek
+1 received by user: 2192

#2621976 15-Dec-2020 12:55

Related question. What diameter hole do you need to concrete in a 125x125 pile? I've borrow a post hole digger, but the auger is only 200mm diameter and I'm not sure if I'll need to widen the holes a little?

Ruphus

469 posts

Ultimate Geek
+1 received by user: 181

#2621993 15-Dec-2020 13:37

Paul1977:
Related question. What diameter hole do you need to concrete in a 125x125 pile? I've borrow a post hole digger, but the auger is only 200mm diameter and I'm not sure if I'll need to widen the holes a little?

Table 6.1 of 3604 has the footing size. 200mm (sq) appears to be the minimum but it all depends on the span of your joists.

HP

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chevrolux

4962 posts

Uber Geek
+1 received by user: 2638
Inactive user

#2622002 15-Dec-2020 13:56

Have you seen the Mitre 10 guide?....

https://www.mitre10.co.nz/guides-and-advice/guide/how-to-design-a-deck

Download that PDF, and it walks you through each step and keeps it inline with the regs.