Advice Needed: Construction of Merbau Platform Steps

maxer81 · Mar 12, 2014 5:33 pm

Hi,

Just seeking some advice on constructing 5 platform steps.
I currently have a 1m high deck in my backyard. I would like to construct platform steps (each step 1200mm wide by 1200mm long) leading up to the existing deck. With the highest platform a 180mm step down from the existing deck (so finished deck height on this platform would be at 820mm off the ground). My question begins with this platform: Initially I was thinking I would construct the platform frame by fixing 90x45 treated pine onto the face of the 4 posts (at 801mm off the ground to allow for 19mm deck that will be concreted in once I work out how I will construct the frame) using nails and batten screws, then nail and batten screw two joists in at the same level (same as a wall frame) and simply lay the deck ontop, then proceed to the next 180mm step down platform and repeat the process by fixing the next 90x45 frame off the two posts I have already concreted using nails and batten screws and onto the face of two more posts I will concrete in 1200mm from the last pair. Is this technique structural? or am I better off sticking with the traditional way of fixing bearer on top of post and joist on top of bearer? the only thing I can't get my head around doing it that way, is that each platform would require four posts meaning two posts from the previous platform will be right infront of two more posts a step down for the next platform.

Sorry if I'm not explaining things enough or lacking depth of detail but hopefully someone understands what I'm trying to work out!

Cheers.

Stewie D · Mar 14, 2014 8:18 am

You'd be using more posts than you really need doing it that way. Each two posts at the rear of each landing should also support the joists or bearers for the next one up as you indicate in the first half of your description.
I'd bolt the bearer to the posts parallel to the front of the step then have four joists sitting on that @ 90º.
If I've got time I'll do a quick drawing this morning.

Stewie

maxer81 · Mar 14, 2014 12:18 pm

Cheers Stewie, that would be much appreciated!

In saying that, is using 90x45 treated pine as a bearer "structural" in this case? or should I be looking at 140x45 as the bearer?

Stewie D · Mar 14, 2014 2:34 pm

Something like this... ?
http://i1212.photobucket.com/albums/cc455/stewiesno1/WoodenSteps_zpsb8fe8f54.jpg

Stewie

Stewie D · Mar 14, 2014 3:14 pm

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All green coloured timber = treated pine - other is merbau 90 x 18mm decking.
90 x 90 posts
90 x 45 joists
90 x 45 upper bearer ( not really a bearer as it sits on the joists below but it is probably the easiest way to get your 180 step height )
140 x 45 lower bearer.
Just make sure you get the treated pine posts that are rated to go in the ground.
I'd also concrete in the base of these for a footing pad and fix the bearers to the posts with gal bolts.

Stewie

maxer81 · Mar 15, 2014 6:11 pm

Onya Stewie!!!
That is spot on mate, I really appreciate your time and detail, I'll let you know how it pans out once I get around to doing it.
Thanks again mate!

maxer81 · Nov 15, 2015 11:11 pm

*Bump*

So, almost two years on I've finally found the time to get the ball rolling on this project!

Just a couple of fixing and structural questions using the design method Stewie has advised, to whom can answer them.

First of all, slight change of that I won't be digging holes for the posts as the surface is now a concrete slab. Will be using the Pryda bolt down post anchor stirrups and Ramset 10x100mm AnkaScrews. The first question begins here.

1. The slab is on a slight slope, so to make the posts level when sitting in the stirrups can I pack under one side of the stirrup on the concrete with either plastic window packers or cut up some joist hangers and then bolt down the stirrup so when I place the post in, it will be near enough level? or bolt the stirrup down with the fall of the sloped concrete then pack under the post in the stirrup?

2. Should I use 1 or 2 M10 Bolt, Nut, Washer to fix post to stirrup? (Or 1xM10 and 1x100mm Batten screw)

3. Should I use M10 bolts in only the 140x45 bearers and just nail and batten screw the 90x45 "upper bearer" to the face of the post? or bolt both?

4. Although the posts will be off the ground sitting in the stirrups, is it over kill to water proof the bottoms?

Thanks in advance guys!

StructuralBIMGuy · Nov 16, 2015 8:51 am

Hi Maxer81
A 1 metre high deck will require planning/building approval, and a structural plan from an Engineer by your council
Please check with your Local Council

maxer81 · Nov 16, 2015 10:20 pm

StructuralBIMGuy

Hi Maxer81
A 1 metre high deck will require planning/building approval, and a structural plan from an Engineer by your council
Please check with your Local Council

Appreciate the reply mate,

However, what made you think I was building a deck? and specifically one at a metre high?

Maybe you should re-read the original post and all of the replies to get a jist of what's actually going on here.

Then maybe you could help with the recent questions involved as you seem to be a person who would know.

Cheers.

Stewie D · Nov 18, 2015 10:11 am

Use galv bolts for most of the post to bearer and the post to stirrup connections. Ant stuff ups or re-levelling required and it is easier to resolve than trying to pry out nails. A bit more up front costs but well worth it. You could dig the holes, assemble most of the frame and attach the stirrups before you pour the concrete. Just temporarily support everything and you shouldn't need any packing for anything.
Waterproofing the bottom of the posts certainly wouldn't hurt.

Stewie

maxer81 · Nov 18, 2015 5:57 pm

Stewie D

Use galv bolts for most of the post to bearer and the post to stirrup connections. Ant stuff ups or re-levelling required and it is easier to resolve than trying to pry out nails. A bit more up front costs but well worth it. You could dig the holes, assemble most of the frame and attach the stirrups before you pour the concrete. Just temporarily support everything and you shouldn't need any packing for anything.
Waterproofing the bottom of the posts certainly wouldn't hurt.

Stewie

Cheers Stewie!

However as I said, there's a slight change as I won't be digging holes or pouring any concrete as the surface is now a concrete slab. Going to use the Pryda bolt down post anchors, which only require AnkaScrews/Dyna Bolts.

So still seeking some advice on question 1?
And question 3 (are bolts required for 90x45 "upper bearer" if the 140 will already have them)?

Thanks!

Stewie D · Nov 18, 2015 10:46 pm

Yeah, get the stirrups as level as possible by any means. Plastic wedges are a good idea.
I'd still bolt the upper bearer as well.

Stewie

maxer81 · Nov 20, 2015 9:12 pm

Stewie D

Yeah, get the stirrups as level as possible by any means. Plastic wedges are a good idea.
I'd still bolt the upper bearer as well.

Stewie

Really appreciate your time and advice Stewie.

Good on ya mate ??