Wrexters Deck Build

**wrexter** · 6th Feb 2016, 06:10 PM

Hi All,

I would greatly appreciate some advice: as I am soon about to embark on my decking for my landscape project (which i am covering here: WREXTER'S REAR LANDSCAPING JOURNEY).

Total area is about 40sqm, looking at using the following:

I have built a Jarrah deck in the past with my father in law, but it was smaller.

Decking Boards: 20x89mm Jarrah (Picture framed)
Joists: 90x45 MGP10 Treated Pine
Bearers: 2 x 90x45
Posts: 300mm x 90mm Pryda Stirrups

Dimensions & Layout:

Below sketch shows the dimensions & overall layout. The red lines show where there is a wall:

Sub-Structure Layout:

Bearers are spaced @ 1200 centres but some are @ 1000 centres as shown. Joists are @ 450 Centres max. As the deck is picture framed, i have had to triple up on joists on some sides as the section sketch below will show:

A few questions:

1. are the double 90x45 bearers an overkill?
2. What is the maximum spacing i should run the joists? or is the 450mm spacing optimum?
3. is the 50mm gap clearance (between bottom of bearer and sand) sufficient? i already have to dig out 4 cubes of sand to bring down levels

4. should i place anything on top of the sand (Perth) before i start laying boards. i.e. weed mat, blue metal etc.

If anyone has any reccomendations on where i can best source all the timber here in Perth for good prices, i would be very appreciative. Best price i have found so far for 22x90mm Jarrah Decking is from Absolute Timbers, $45 per square meters.

Thanks for the help in advance.

Cheers

**PlatypusGardens** · 6th Feb 2016, 06:17 PM

Hello and welcome

Originally Posted by wrexter

1. are the double 90x45 bearers an overkill?

2. What is the maximum spacing i should run the joists? or is the 450mm spacing optimum?

3. is the 50mm gap clearance (between bottom of bearer and sand) sufficient? i already have to dig out 4 cubes of sand to bring down levels

4. should i place anything on top of the sand (Perth) before i start laying boards. i.e. weed mat, blue metal etc.

1. Not overkill I usually go double 140x45.
Bigger bearers = greater span = less holes to dig

2. 450mm centers max

3. I would think that's ok for Perth sandy conditions, but others may disagree

4. I wouldn't, but again - others may disagree.

**wrexter** · 7th Feb 2016, 05:39 PM

Thanks for the reply

Was just reading koppers build thread and looks like as he did I will have to leave a 20mm gap go house for termite inspections. Therefore I can't install wall plates to house .

**wrexter** · 9th Feb 2016, 01:27 PM

I have re-designed the deck structure. as there needs to be a 20mm gap to the house (for termite protection warranty) the deck is now mostly freestanding, except in one spot where it needs to be tied using a wall plate as i am limited by installing another post.

as you can see, to achieve a picture frame, i will need to install 3 x joists on the sides.

from the deck span tables i can see that with the 2 x 90x45 MGP10 bearers, i can install posts @ 1900 ctrs. my posts area spaced at mosly ~1600 ctrs or 1250 ctrs. am i over engineering this, should i go up to under 1900 spacing to reduce posts? would it still be rock solid so to speak?

bearers are spaced @ 1200 ctrs, joists are spaced at 450 max ctrs.

feedback appreciated.

**David.Elliott** · 9th Feb 2016, 03:31 PM

Try THE TIMBER BLOKE | Timber for any project you have in mind

Used him recently. Boards are all air dried, then KD, then milled to order...

**Bloss** · 10th Feb 2016, 05:50 PM

As I say often close up the spaces for bearers and/or increase sizes and close up spaces on joists too. Costs very little to do so and makes a big difference to the 'feel' of the deck. Minimum standards (e.g.: maximum spans for bearers of a particular size or max 450mm centres for 90x45 joists) are the worst you are allowed to do by law - not the best of even good practice! I know that what people do and if you are trying to make buck then doing what is the minimum can make sense, but if you are building it for your self then building better makes more sense IMO. So PlatypusGardens on using larger bearers (and reduces the number off holes to dig too!) with closer spans and reducing even to 425 centres rather than 450mm will make for a better deck. Just my view of course . . .

**maxdacat** · 10th Feb 2016, 10:45 PM

Wait, so you are planning then building.....interesting

**wrexter** · 11th Feb 2016, 12:12 AM

Originally Posted by maxdacat

Wait, so you are planning then building.....interesting

haha is that not the norm around here?

Anyways, considering whether to go 90mm or 140mm wide boards, im leaning towards 140mm due to the size of the area but still not sure. i did a layout, but still not 100%, any thoughts?

Also, wanted to get your thoughts on the best way to layout my framework so support the picture frame timber boards:

I have see both methods below and my preference is now option B (right) to reduce length of joist used, thoughts?

**Marc** · 11th Feb 2016, 07:53 AM

Do you have to have such a complicated perimeter? Doing the picture frame is not going to be much fun.
140mm wide decking boards must be better than 19mm thick or they will cup.

**PlatypusGardens** · 11th Feb 2016, 09:21 AM

Originally Posted by maxdacat

Wait, so you are planning then building.....interesting

Yeh....where's the fun in that?

**David.Elliott** · 11th Feb 2016, 11:01 AM

Yeah...could that possibly be where I've been going wrong all these years.

Much easier to build, then make the plans to match. Impress your friends with your new found ability to make, draw and follow plans.

**PlatypusGardens** · 11th Feb 2016, 11:16 AM

Originally Posted by David.Elliott

Yeah...could that possibly be where I've been going wrong all these years.

Much easier to build, then make the plans to match. Impress your friends with your new found ability to make, draw and follow plans.

Hahahaha

I just dig a bunch of holes and start concreting stuff in the ground and go "bugger, that should have been over there"

**Bloss** · 11th Feb 2016, 11:28 AM

BTW - if you haven't already list Forum member Blocklayer's site Deck Calculator - Metric

**Marc** · 11th Feb 2016, 12:13 PM

Originally Posted by David.Elliott

Yeah...could that possibly be where I've been going wrong all these years.

Much easier to build, then make the plans to match. Impress your friends with your new found ability to make, draw and follow plans.

Hei ... that is what I do all the time

Only no one to impress really.

**wrexter** · 11th Feb 2016, 02:39 PM

Unfortunately yes, the deck is fitting around an alfresco, planter boxes, pizza oven stand etc.

Originally Posted by Marc

Do you have to have such a complicated perimeter? Doing the picture frame is not going to be much fun.
140mm wide decking boards must be better than 19mm thick or they will cup.

**Snipper** · 13th Feb 2016, 12:48 AM

I'd use a 90 mm border / picture frame and 140 for the rest. I usually use a 90 x 45 joist doubled up and hang the 90 mm border / picture frame over the outside edge 25 - 30 mm then a butt a baseboard up underneath and screw into that.

**wrexter** · 14th Feb 2016, 02:10 PM

Can you please show me a photo of your deck. Would love to see 90mm border with 140 boards

**PlatypusGardens** · 14th Feb 2016, 02:16 PM

Originally Posted by wrexter

90mm border with 140 boards

I did that here http://www.renovateforum.com/f82/tim...ogress-100341/

Ok....not a lot of border.....but I also did the opposite and framed the 90mm boards with 140mm on the seats....

**wrexter** · 21st Jun 2016, 02:03 PM

Bit of an update on this deck, bearers are in!

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