Calculate the price of a deck - Mother of all posting!!

very informative post. i was quoted $4k by our builder to put decking in our alfresco on a concrete base. i initially thought this was an outrageous price for a few planks of wood, but after reading this it sounds almost reasonable.

I'm a bit confused by the "Decks under the building code must be a minimum of 300mm above the ground" comment. My Draughtsman did a Ground Level Deck/Pergola Plan where the Bearers sit just 25mm above the ground! The Bearers are 100mm x 100mm Galvanised steel, and the Joists are 100mm x 50mm Galvanised Purlin. Council have approved the Plans and I thought that everything was above board and legal, the Pergola roof will be attached to the House Roof using Roof Extenda Brackets so I want to keep everything nice a legal with regard to my Home Insurance.
Is the 300mm above ground for the bottom of the Bearers, or the top of the Decking?
Does using Galvanised Steel instead of wood allow me to go closer to the ground than using wooden Bearers?
Thanks for any information that anyone can supply as I am halfway through the project and have spent roughly $6k so far, so I would hate to find out it was not legal!!

300mm to the bottom of the decking according to the manufacturers - this includes composite decking such as Modwood
An issue when built closer is the moisture levels under the deck, I have seen 4"hardwood boards cup and lift and snap screws on a deck built approx 150mm above the ground where the ground was very damp constantly.
If its over concrete or the ground has good run-off I don't imaginethere would be as much an issue

It's also a good idea to run some 90mm ag pipes under the deck and take any surface water away from underneath. Water sitting thei constantly will take a while to get away as the decking will provide shade for it and wont dry up as quick. Weeds can also grow up through the boards and can be problematic to control

Good idea with the ag pipe. I normally recommend people lay down weed mat to stop weeds growing through when they are that low

OK, thanks for the information. I should have 225mm from ground level to the bottom of my Decking (Stringybark Hardwood), and there will be no pooled water as there are a series of gravel filled trenches under the Deck to carry away any rain water.
Is the 300mm a legal requirement or just a recommendation? I am still a bit concerned about keeping things 100% legal for my Home Insurance.

I found the following information at another Forum, so now I am really confused
Is the 300mm to the bottom of the Decking a Recommendation or a Legal Requirement?
Thanks to the Experts for any guidance that they can give so that I can sleep a bit sounder at night.



Quote:
Originally Posted by Spider Webb View Post
My council (Hornsby NSW) requested minimum 400mm clearance between underside of the lowest timber member and the finished ground level for visual inspection of termite barriers in accordance with Parts 3.1.3 and 3.1.4 of the Building Code of Australia and AS3660.1-2000.

Hope that helps.

Stewart
That's not for decks - most of which are Class 10 (BCA) structures. A deck can sit on the ground if need be so long as it is built using the appropriate treated timber ie: H4 or H5 for timber that is contact with the ground. Generally if the deck is close to the ground the edges are closed in so leaves etc do not build up underneath, but shrubs and plantings can do the same job. Ventilation is rarely an issue for any deck - it will have gaps between the boards at the very least.

Hi All, my first post on this site. I've been enjoying reading the good info - thanks to all!

We are considering building a 3.4 x 6.6 timber deck 400mm above ground level, with polycarbonate roofing / gutter to a water tank. Got an initial quote for $10,260 (including the 5,200 litre tank, worth $900) done in pine. And we have to do all the painting for this price.

I roughly estimated the materials (excluding the tank) at about $2500, up to $3000 max. So it surprised me that the approx labour must be about $4500-$5500. Seems a bit steep.

More than 20 years ago I built a couple of decks myself, and tried to remember how much time it took klutzy me to do the jobs (one was similar size). But it couldn't have been more than about 6 days.

Questions....
1/ What is the estimated fully built cost for decking including polycarbonate roofing, per square meter these days?
2/ We are in Glen Iris, Melbourne. Can you recommend a good tradesman working in the eastern suburbs?

(or maybe I just have to drag the old tools out of the garage, and diy.... )

ohhhhhh can we have a dvd toooooooooooooooo?? been a year for us and still a pile of dirt and weeds

Hi,

We recently just moved to our new house. Its time for me to build a deck.
My area is about 4.4 x 4.5



Looking at Duke's comments, I can have the distance of the bearers about 1.5m of each other. If this is the case, what should be the distance of my posts? it 1.46m enough?

if I will be using the same bearers as wonderland (2 90x45), can I use 90x90 posts? if yes how can I rebate the bearers to the posts?

What if I use 90x90 post, 140x45 bearers and 90x45 Joist is this ok? can I still use the same distances for posts, and bearers? but for bearers I will only use 1 140x45?

Thanks

Thanks

Can anyone give me a company name that does decking at a reasonable price?

Hi guys,

I'm planning out my decking now while my house is being built, I have done a bit of research and put figures into websites to tell me what I need. I just want to know if im on the right track. Then I can start pricing it all.

here are some pics of the decks i plan to build

Alfresco

Verandah

Entry

What sort of timber are you planning on using?
You have joist 100 x 50 mm (normally not seasoned) and bearers 90 x 45 mm
Do you have space below deck to increase bearer size (less holes, posts, concrete)

I think the best advice I can give you is get a copy of the F5 span tables used in the AS1684-2010 (people post it in places, use google) and work out the spacing from this. I used the program you have used when I was starting out and designed it completely differently after getting the tables. If you can, get a copy of AS1684.4-2010, it explains everything you need to know about designing properly.

In order of how to design, work out which way you want your boards to run (this governs the direction of bearers and joists). Then work out your ground clearance to determine the size of structural timber you will need to use (the most common joist/bearer sizes are 90x45 or 140x45). If you can, 140x45 is ideal as it allows long spans between bearers and posts. The bearers will be nail laminated (ie. 2/140x45, nailed together with the grains running in opposite directions).

Space your joists at a maximum of 450mm.

Be aware also that your Alfresco Deck may require a permit (in my council any deck over 10 squares needs one). Check with your council now so your aware.

As far as other comments on your plans,

* is there a reason you have chosen 70mm boards and not 90mm?
* The cantilever on your bearers appears too large for all three decks (the unsupported part of the bearer that runs past the last post. for 2/90x45, max is about 400mm depending upon floor load width
* Change your joists to 90x45 or 140x45 (90x45 may mean you need another line of bearers)
* Make sure any joist cantilever (unsupported part of the joist that runs past the last bearer) is within spec
* I think a border around the deck looks great (like a picture frame). Consider doing this?

Hi Freddo,

What program have you used their for your designs?

Looking for that noobies guide to building decks. Need to build one for the front portico. half on concrete and half on soil.

Hi guys,

I'm looking at building my own deck for our alfresco area and also extending it out either side of it, after reading through the thread I've got some of the information I need, but need a few more details and just wanted to clarify some things...

Our deck is going to be on ground level, can't go more than 2 brick courses up from concrete slab due to termite mesh laid between the 2nd and 3rd bricks. I got a quote from a local pergola/decking installer, he quoted $8k.

He's quoted us on bearers 200x75mm, joists 100x50mm, decking merbau 90x19mm - do my joists and bearers need to be that tall?



In the diagram attached, the bearers are going top to bottom, joists left to right, and decking top to bottom. I've read that joists have to be 450mm apart which is fine, I'm unsure of what spacing the bearers are to be spaced apart and how many posts (stirips concreted into the ground) that I will need/spacing apart?

The blue lines is where I was thinking of bolting joists onto (I read that it shouldn't be done but is the house really going to move that much?) the brickwork, running bearers under that which will be supported by the stirips. The orange square is our alfresco area.

I was also told about a place in Melbourne (I'm in Sydney) from a friend of mine called no nail decking which is a little bit more expensive but you don't have the nails showing (only on the edges), has anyone used this or heard of it? good or bad feedback?

Does anybody know of a cheap timber supplier in western Sydney? I checked out bunnings last weekend and they seem expensive..

Any help/feedback is greatly appreciated guys.

Dave.

My deck is similar to yours, i used 250x90 bearers, 90x45 joists, and 90x19 decking boards.

got the timber for the carcass from Macarthur landscape supplies, and the decking boards from Abbey Timber (was about $3.60/lm)

Has anyone got any photos of their DIY Decks? And can you say whether you regret your DIY or are happy you gave it a go?