Double carport with deck above

Forums › Home Workshop DIY › Double carport with deck above

blackjack17

1705 posts

Uber Geek

#269834 10-Apr-2020 11:27

Just a thought / proof of concept exercise but I am trying to calculate the rough cost of a double carport with a deck on top.

We have a 6m by 6m dug out bank with a concrete pad and retaining walls to 1.5m. I would like to build something like this with the ceiling height being at 2m

With a deck on top (couldn't work out how to hide the joists in sketchup).

Is it just me or is sketchup way harder to use now than it was a few years ago

Couple of questions.

Am I running the bearers the right way? i have each bearer supported by two piles.

Would it be better to run two bearers along the piles and then the joists across the 6m span?

But this would lead to needing massive joists so having two sets of bearers might be better? Have two bearers run along the piles and then span the 6m carport with probably flitch beam bearers and then joists on top.

I know at some stage will need to consult an engineer and get consent but just trying to get a rough calculation so we can put it in the spending timeline.

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wellygary

8321 posts

Uber Geek

#2458835 10-Apr-2020 11:50

Having a deck for people on the top is going to increase your compliance processes ( and $) by a fair whack,

At 6*6 you exceed the 20 sqm exemption for car ports so you are going to need a consent from your local council,

https://www.building.govt.nz/projects-and-consents/planning-a-successful-build/scope-and-design/check-if-you-need-consents/building-consent-exemptions-for-low-risk-work/schedule-1-guidance/part-1-exempted-building-work/18-carports/

blackjack17

1705 posts

Uber Geek

#2458836 10-Apr-2020 11:53

wellygary:
Having a deck for people on the top is going to increase your compliance processes ( and $) by a fair whack,

At 6*6 you exceed the 20 sqm exemption for car ports so you are going to need a consent from your local council,

https://www.building.govt.nz/projects-and-consents/planning-a-successful-build/scope-and-design/check-if-you-need-consents/building-consent-exemptions-for-low-risk-work/schedule-1-guidance/part-1-exempted-building-work/18-carports/

Yep any double carport requires consent

But this gives us another 36m2 of useable back yard and long term plan is to put a pool in so this would make up for the loss of yard

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elpenguino

3423 posts

Uber Geek

#2458858 10-Apr-2020 12:15

Don't forget, if your deck is big enough to hold 100 people it needs to be strong enough as well.

</Six60>

I would suggest steel for such a long span.

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afe66

3181 posts

Uber Geek

Lifetime subscriber

#2458868 10-Apr-2020 12:30

We have a deck over the top of your standard 1970's breeze block garage and the deck has extra ?4x4" supports in addition to the concrete block walls.

So are your walls in the picture strong enough?

We have plans to knock our garage down and replace it with a study workshop with a deck running the entire length. Its a two car garage (nose to tail car parking). Will dig down a meter or so to create normal ceiling height inside the extension. The deck will be built over its entire length except for a sky light at the far end over the study.

We needed to get council and neighbour consent as its also close to the boundary.

(Also discovered the true boundary is in the neighbours section but thats another story)

blackjack17

1705 posts

Uber Geek

#2458873 10-Apr-2020 12:37

afe66:
We have a deck over the top of your standard 1970's breeze block garage and the deck has extra ?4x4" supports in addition to the concrete block walls.

So are your walls in the picture strong enough?

We have plans to knock our garage down and replace it with a study workshop with a deck running the entire length. Its a two car garage (nose to tail car parking). Will dig down a meter or so to create normal ceiling height inside the extension. The deck will be built over its entire length except for a sky light at the far end over the study.

We needed to get council and neighbour consent as its also close to the boundary.

(Also discovered the true boundary is in the neighbours section but thats another story)

They aren't walls. That is the existing retaining wall.

I'm picturing it as a standalone deck 2m high with a 6m span

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evilengineer

466 posts

Ultimate Geek

#2458889 10-Apr-2020 13:06

blackjack17:

Am I running the bearers the right way? i have each bearer supported by two piles.

Would it be better to run two bearers along the piles and then the joists across the 6m span?

But this would lead to needing massive joists so having two sets of bearers might be better? Have two bearers run along the piles and then span the 6m carport with probably flitch beam bearers and then joists on top.

I know at some stage will need to consult an engineer and get consent but just trying to get a rough calculation so we can put it in the spending timeline.

Not to sure about your building terminology, to my mind you've drawn a series of four "frames" at 2m centres that consist of beams spanning 6m onto timber posts at each end.

I'd suggest you could probably get that down to three frames (front,middle and back) with joist at 450m centres spanning 3m between each frame and with the decking boards on running left to right over the top of the joists.

You are right that 6m is a pretty big span for timber. You could go with a pair of beams in each frame (probably still 240 or 290 deep) or maybe Glulam or LVL.

Can you get flitch beams for external use? The steel plate would need to be galvanised at least and the timber throughout would need to be H3.2.

Plus you'll need a balustrade (should be suitable details for a domestic situation in NZS3604) and unlike a carport thought will be required to determine how it stands up in an earthquake.

blackjack17

1705 posts

Uber Geek

#2461926 15-Apr-2020 14:14

I am kind of picturing a cross between these two (encountered when randomly walking)

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Brunzy

2016 posts

Uber Geek

Trusted

#2461953 15-Apr-2020 14:35

So , what you’re really looking at is building a deck you can park under, may be easier to get consent.
I suspect you would need another beam running down the middle, there are specs to say how far you can span / cantilever with different joists , how far apart the centres need to be etc.

mrfee

20 posts

Geek

#2462122 15-Apr-2020 19:38

What does the proposed access to the deck look like? I imagine having to build stairs with appropriate balustrading up to the deck from below will add a fair bit more cost than using existing access already at the required height if it exists.

We are actually planning something similar at home so are very interested in this thread and any info you get about a very rough cost.

blackjack17

1705 posts

Uber Geek

#2462130 15-Apr-2020 20:19

This is the area that we hope to have covered. the retaining wall comes to 1.5 m If the deck top is 2.3 then it would only be an 800mm step up to the deck.

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andrewNZ

2487 posts

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Inactive user

#2462143 15-Apr-2020 20:40

The cost could vary considerably based on: the type of ground and the foundations required, the area wind zoning, the intended use (do you want it to support a spa pool, etc

As this wasn't allowed for when the driveway was done, you will probably need to have the concrete cut and proper foundations put in.

The main supporting structure will more than likely need to be all steel, and that might be >$10k alone.

I really have no idea how much, I'm pulling numbers from my butt. However, if you came back in a few months and said the quotes were $30k for the build alone, it wouldn't surprise me in the least.