Deck building calculator / help for prices

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6434 posts

Uber Geek

#767361 21-Feb-2013 23:03

Wilko: If any part of the deck is over 1 metre above ground level, a building consent is required. Also, a deck that is more than 2 metres wide from the house requires bracing to the sub-structure, which has to be calculated by someone who knows how to do the calculations!
Even though a permit may not be required, the structure still has to comply with the Building Act. Usually you need to use NZS 3604 as the guide for pile spacing, and bearer and joist sizes and spacing. If there is greater than 1 metre from any of the deck edges to the ground, an approved handrail must be included.
I think that both Placemakers and Mitre 10 have pamphlets which help with building a simple deck, with suggested sizes of joists and bearers. That may give you an idea of how to go about planning and building what you want.
Also, there may be resource consent issues if the additional area of the deck takes the total site coverage over that allowed by the Council's district plan. If you are on a cross-leased section, there may be requirements for obtaining the other people's approval and the plan of the deck may have to be added to the Survey Title (which means lawyers!!).

The rules were changed last year I think. You can build up to 1.5m off the ground now without consent.

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superoman

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Geek

#767362 21-Feb-2013 23:07

Hi
I estimate / order building materials as part of my job

Ill specify a list tomorrow for you

If the piles are 1.6m apart, the bearers can be 2/140x45

Peter

Niel

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#767380 22-Feb-2013 05:48

jonherries: On the Australian "The Block" in the last series, they had some sort of clip in system so no nails and screws. Not sure what the product is but the finished article was impressive.

Jon

Edit: sp

I remember that, it was like a shark tooth stainless Z-plate that you hammer sideways into the decking and then the plate nails/screws down onto the bearers (or do you call them joists?). Looked great. Might find it at boat builders? Again, Anzor is one place to look at because they do only stainless and supply lots of stuff for marine use.

You can never have enough Volvos!

Niel

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#767382 22-Feb-2013 05:55

mattwnz: Best to check with the council anyway to see if a consent is required. Some TAs have their own rules. I think the NZ building cose also has the rules for decks, and that is free on the dept of building website. NZS3604 will have the calculations you need in terms of piles and bearer spacing and sizing, and bracing. Free access at your library to this.

Our neighbour phoned the council a couple of months ago when we wanted to replace the fence at OUR cost to look the same as all the other new fencing we've done. The neighbour phone the council who told them any fence over 1.8m needs a consent. The clerk you get on the phone does not know their own rules, their web site says 2.5m as per the recent code changes.

The only way to get an accurate answer from council is to have a meeting which will cost you a deposit and then after the meeting they will invoice you for the actual cost. Been there, done that.

With Manukau Council all info was on their web site, but now we are integrated into Auckland Council and the web site has very limited information with contradictions. (End of rant.)

Regarding spacings, minimum code is just minimum code for safety and you'll have a much more solid deck if you increase the piles/bearers. Safe does not equal solid, go better than minimum code.

You can never have enough Volvos!

NonprayingMantis

6434 posts

Uber Geek

#767428 22-Feb-2013 09:29

Niel:
mattwnz: Best to check with the council anyway to see if a consent is required. Some TAs have their own rules. I think the NZ building cose also has the rules for decks, and that is free on the dept of building website. NZS3604 will have the calculations you need in terms of piles and bearer spacing and sizing, and bracing. Free access at your library to this.

Our neighbour phoned the council a couple of months ago when we wanted to replace the fence at OUR cost to look the same as all the other new fencing we've done. The neighbour phone the council who told them any fence over 1.8m needs a consent. The clerk you get on the phone does not know their own rules, their web site says 2.5m as per the recent code changes.

The only way to get an accurate answer from council is to have a meeting which will cost you a deposit and then after the meeting they will invoice you for the actual cost. Been there, done that.

With Manukau Council all info was on their web site, but now we are integrated into Auckland Council and the web site has very limited information with contradictions. (End of rant.)

Regarding spacings, minimum code is just minimum code for safety and you'll have a much more solid deck if you increase the piles/bearers. Safe does not equal solid, go better than minimum code.

I'm of the opinion that minimum code is, in many cases, far more than is actually needed.

for example, the OP has a deck that is only 50cm off the ground. by the time you allow for the deck (2.5cm) the joist (~15cm thick) and bearer (20cm thick) your pile is actually only going to stick out of the ground about 12.5cm. Thus is there really any point in having bracing?

I’ve built plenty of decks that are very low to the ground. The building code assumes decks will be built quite high and so the extra bracing etc is needed for that.

But really, if it is quite a large one and sufficiently low (say, 20-30cm above ground level) you don’t even need piles at all since the weight of the deck itself plus a few H5 50x50 stakes hammered into the ground and nailed to the structure will keep it in place just fine.

Goosey

2336 posts

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#767431 22-Feb-2013 09:37

Theres the old saying "check before you dig" i.e. any power, wastewater, sewage and phone lines in that area?
How far down are you piles going? will this deck become an issue if any of those services are underneath e.g. access to drains for block drain cleaning etc?

NonprayingMantis

6434 posts

Uber Geek

#767435 22-Feb-2013 09:42

Gooseybhai: Theres the old saying "check before you dig" i.e. any power, wastewater, sewage and phone lines in that area?
How far down are you piles going? will this deck become an issue if any of those services are underneath e.g. access to drains for block drain cleaning etc?

if the piles only need to stick out 12cm, then they only need to be buried 20cm into the ground.

there should be no utility pipes or cables buried that shallow.

Goosey

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#767574 22-Feb-2013 12:34

Out of interest are you laying weed matting under the deck?

I find it a pain trying to weed spray the odd weed from time to time.

Wilko

60 posts

Master Geek

#767578 22-Feb-2013 12:38

NonprayingMantis:
Gooseybhai: Theres the old saying "check before you dig" i.e. any power, wastewater, sewage and phone lines in that area?
How far down are you piles going? will this deck become an issue if any of those services are underneath e.g. access to drains for block drain cleaning etc?

if the piles only need to stick out 12cm, then they only need to be buried 20cm into the ground.

there should be no utility pipes or cables buried that shallow.

The requirement for a deck is that the piles must extend to "Good Ground", then tries to explain what good ground is (it is fairly complicated!). The absolute minimum footing size is 200x200x200 concrete with the pile bedded so there is 100mm of concrete beneath it. The actual footing size depends on the bearer and joist spans. If anchor piles are required for bracing purposes, they are required to be 900mm deep.
The design of a deck is based on 2kPa floor loading, wet in service timber.
If a building consent is required, the design and construction must be carried out by a Licenced Building Practitioner. However, the Building Act was changed last year to allow minor works to be carried out by an owner but they are still subject to council inspections. The definition of minor works is really only determined by the council and their definitions may vary, but I am pretty sure a deck would be classed as minor.

NnprayingMantis -

AFAIk you don't need a permit for a new deck unless it is more than 1.5m off the ground

If you go to http://www.dbh.govt.nz/blc-building-consentinspect-process#map1, some examples of what requires or does not require a consent are given. You will see that any deck over 1 metre high does require a consent. Retaining walls only require one if over 1.5 metres. Maybe that is what you were thinking of.

timmmay

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#767580 22-Feb-2013 12:39

Consider what the water will do under there, you don't want it going under the house. When I redo my deck I'll do some kind of concrete foundation to channel water toward the drainage system.

Goosey

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#767588 22-Feb-2013 12:46

stamped / coloured / brick / slab concrete pavers with raised edged garden/planters anyone?
dedicated bbq area.

Would be easy to clean, wont rot, wont stain as easy... you still retain some sort of garden type look !

Goosey

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#767591 22-Feb-2013 12:48

ya wont have to worry about loading, the deck pulling off the house/garage, council consents

NonprayingMantis

6434 posts

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#767630 22-Feb-2013 13:32

Wilko:
NonprayingMantis:
Gooseybhai: Theres the old saying "check before you dig" i.e. any power, wastewater, sewage and phone lines in that area?
How far down are you piles going? will this deck become an issue if any of those services are underneath e.g. access to drains for block drain cleaning etc?

if the piles only need to stick out 12cm, then they only need to be buried 20cm into the ground.

there should be no utility pipes or cables buried that shallow.

The requirement for a deck is that the piles must extend to "Good Ground", then tries to explain what good ground is (it is fairly complicated!). The absolute minimum footing size is 200x200x200 concrete with the pile bedded so there is 100mm of concrete beneath it. The actual footing size depends on the bearer and joist spans. If anchor piles are required for bracing purposes, they are required to be 900mm deep.
The design of a deck is based on 2kPa floor loading, wet in service timber.
If a building consent is required, the design and construction must be carried out by a Licenced Building Practitioner. However, the Building Act was changed last year to allow minor works to be carried out by an owner but they are still subject to council inspections. The definition of minor works is really only determined by the council and their definitions may vary, but I am pretty sure a deck would be classed as minor.

NnprayingMantis -
AFAIk you don't need a permit for a new deck unless it is more than 1.5m off the ground

If you go to http://www.dbh.govt.nz/blc-building-consentinspect-process#map1, some examples of what requires or does not require a consent are given. You will see that any deck over 1 metre high does require a consent. Retaining walls only require one if over 1.5 metres. Maybe that is what you were thinking of.

I'm thinking of this:

http://www.dbh.govt.nz/UserFiles/File/Publications/Building/Guidance-information/pdf/dbh-guide-for-building-work-consent-not-required.pdf#page=31

"guidance
A building consent is not required for decks, balconies, platforms and bridges, and similar structures where it is not possible to fall more than 1.5 metres."

also here

http://www.aucklandcouncil.govt.nz/EN/RATESBUILDINGPROPERTY/BUILDINGCONSENTS/DOINEEDBUILDINGCONSENT/Pages/Home.aspx

Some examples of exempt building work are:

replacing a hot water cylinder
minor drainage work that does not affect the connection to the public system
replacing windows so long as it doesn’t affect the structural stability of the building
changes to entrance and doorways to improve accessibility so long as it doesn’t affect the structural stability of the building
changes to timber framed internal walls so long as it doesn’t affect the structural stability of the building
walls and fences under 2.5 metres high
decks under 1.5 metres high.

berry

61 posts

Master Geek

#767688 22-Feb-2013 14:55

I always get confused between the 1m and 1.5m - I think 1m is for needing a railing, and the 1.5m is the new consent limit?? But it should be easy to find out from the council (well as easy as getting anything useful from a council, ie not that easy).

I saw those clip in decking systems at our local ITM - they looked kind of nifty but they looked like they would be expensive, didn't actually check how much they were though.

roughly your deck is 8.2m by 4.4m ~ 36m2
Decking (definitely go for the larger grade ex40mm not the ex25mm) average about 94mm wide so 10 boards per m wide is plenty - that would give 360 lm - you have 350m so that sounds right.

Joists - you want these about every 450mm to eliminate any bounce - so across your 8.2 you'll want around 18 joists, without knowing the angle I'lll assume they are max 2.6m long - so about 50m - you had 90m so maybe i've missed something?

I assumed your decking is going same direction as your lines on the new bit??

I think someone else calculated piles and bearers for you.

I'm pretty sure anything going into the ground needs to be H5 these days.

Wilko

60 posts

Master Geek

#767703 22-Feb-2013 15:14

NonprayingMantis:
Wilko:
NonprayingMantis:
Gooseybhai: Theres the old saying "check before you dig" i.e. any power, wastewater, sewage and phone lines in that area?
How far down are you piles going? will this deck become an issue if any of those services are underneath e.g. access to drains for block drain cleaning etc?

if the piles only need to stick out 12cm, then they only need to be buried 20cm into the ground.

there should be no utility pipes or cables buried that shallow.

The requirement for a deck is that the piles must extend to "Good Ground", then tries to explain what good ground is (it is fairly complicated!). The absolute minimum footing size is 200x200x200 concrete with the pile bedded so there is 100mm of concrete beneath it. The actual footing size depends on the bearer and joist spans. If anchor piles are required for bracing purposes, they are required to be 900mm deep.
The design of a deck is based on 2kPa floor loading, wet in service timber.
If a building consent is required, the design and construction must be carried out by a Licenced Building Practitioner. However, the Building Act was changed last year to allow minor works to be carried out by an owner but they are still subject to council inspections. The definition of minor works is really only determined by the council and their definitions may vary, but I am pretty sure a deck would be classed as minor.

NnprayingMantis -
AFAIk you don't need a permit for a new deck unless it is more than 1.5m off the ground

If you go to http://www.dbh.govt.nz/blc-building-consentinspect-process#map1, some examples of what requires or does not require a consent are given. You will see that any deck over 1 metre high does require a consent. Retaining walls only require one if over 1.5 metres. Maybe that is what you were thinking of.

I'm thinking of this:

http://www.dbh.govt.nz/UserFiles/File/Publications/Building/Guidance-information/pdf/dbh-guide-for-building-work-consent-not-required.pdf#page=31

"guidance
A building consent is not required for decks, balconies, platforms and bridges, and similar structures where it is not possible to fall more than 1.5 metres."

also here

http://www.aucklandcouncil.govt.nz/EN/RATESBUILDINGPROPERTY/BUILDINGCONSENTS/DOINEEDBUILDINGCONSENT/Pages/Home.aspx

Some examples of exempt building work are:
replacing a hot water cylinder
minor drainage work that does not affect the connection to the public system
replacing windows so long as it doesn’t affect the structural stability of the building
changes to entrance and doorways to improve accessibility so long as it doesn’t affect the structural stability of the building
changes to timber framed internal walls so long as it doesn’t affect the structural stability of the building
walls and fences under 2.5 metres high
decks under 1.5 metres high.

You are correct - I have learnt something today. It seems as though it has been changed from 1 metre to 1.5, but the old height still has to go through parliament to be deleted! The dbh website is confusing things by having the two different heights in seperate places on their website.

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