help with cementing in stirrups for deck

[marc28]

hi all,

I am building a rear timber deck with pretty low clearance. I am using steel stirrups to lay my bearers on and am not sure how they are supposed to cemented in. How much concrete should be under the base of the stirrup?
and what depth?

any help would be great

thanks

marc

[journeyman Mick]

Marc,
it really depends on the loads imposed by the structure and the bearing capacity of the soil. If there's no roof on your deck (or if these footings aren't taking a roof load) and your backyard isn't a swamp or landfill then 300 x 300 x 600 deep is a good starting point.

Mick

[marc28]

thanks mick,

one more question.....how much concrete should be under the foot of the stirrup. (it is a deck only no roof)

ta

[sandant]

marc
as journyman said also the stirrups shpuld be no more than 7 cm out of the ground as for the concrete im not sure exactly but what i have done and has lasted a few storms so far was to put any bits and pieces of steel you have laying around into the holes for rio then fill your hole up to just below ground level my holes at 600 took about 30 kg bag of concrete.

ok thats about all i have to share with you make sure your stirrups are level a slight slant at the bottom means quiet a large one at the top!

[journeyman Mick]

Marc,
dig your 300 x 300 x 600 hole, fill it with concrete and poke in the stirrup, leaving it up off the concrete by 30 - 50 mm. If you prefer you can set the stirrup up to hang in the hole off a peg and a bit of framing at the correct height and in relation to your stringlines.

Hang on, I just realised you're sitting your bearers on the stirrups, not posts. I'm not sure if they make extra long stirrups for this application, or even wether stirrups would be strong enough if you poke them out a fair way. How far off the ground are your bearers sitting? It would probably pay to set up some profiles and run stringlines so you know where you're at. I wouldn't feel comfortable extending the stirrups out of the footing too far, I'd be more inclined to use a pair of heavy fish plates instead. Stirrups can flex somewhat whereas a pair of fishplates at each footing will take a lot more side loading before they'll flex.


Mick

[marc28]

Mick,

i have run the stringlines and the heighest point will be no more than 100mm.

Haven't heard of fishplates? is 100mm to high out of the ground?

marc

[Geno]

I have set bearers into Pryda stirrups before and had no problems with movement. They come in a range of lengths and the Pryda web-site has all the specs and guidelines you need, but I will think you will find them plenty strong as long as you adhere to the specs as to how far from the footing they can protrude.
In my case the stirrups are being used in a deck that has a 4 ton spa sitting on it so I think you be well safe in a more conventional load bearing scenario.
Highest protusion in my case is about 300mm.

I think the other major brands are pretty much the same (i.e this is not an ad for Pryda).

Depending on soil composition the figures provided by Journeyman are fine - and he would now better than I.

http://www.pryda.com.au/

[sandant]

mark
i have only just got an approval for my deck it will be 2m x 5m/ as part of the approval i had to give dimensions of timber ect, i was told by the approval guy that the stirrups could be no more than 7 cm out of the ground.
thats the shaft part.

[Geno]

I am not sure where this guy is coming up with the magical 70mm out of the ground figure. I can only assume it is a very short stirrup. I have seen stirrups that range in length from 650mm to 6000mm, so surely logic would dictate that the height that the stirrup can protrude from the concrete will vary commensurate with the overall length of the stirrup.
As you need to raise the height out of the ground of the stirrup you simply get a longer one.
My 600mm stirrups are set 300mm into the footing which leaves me with 300mm of height. This option is much better IMHO than setting 20 short stirrups into place and then stuffing about cutting 20 posts to height. Cheaper, stronger, more durable and less work. Not my idea by the way. I was going to order 20 short stirrups and 7 liner meteres of 100x100 timber for the posts until the bloke who runs the timber yard (a chippie by trade) suggested the tall stirrup option. Saved me a heap of work.

An extract from the Pryda specs;
"The distance from the top of the concrete to the underside of the post anchor should not exceed 300mm".

[sandant]

geno
dead right about the length of the stirrup should dictate how high you could have it out of the ground, in my case we are talking about stirrup length of 400mil so maybe thats where hes comming from i also made a slight mistake its 750mil not 700.

did the pryda specs mention about the length of the stirrup?

also those stirrups you used bloody long buggers!!
6000mm thats a 6 metre stirup is this a mistake ?

[alexeib]

My 6000mm stirrups are set 3000mm into the footing which leaves me with 3000mm of height.Gees, stirrup set 3 METERS deep into concrete -- that is going to last. :-)
One too many zeroes or you do have a stirrup that sticks out by 3 meters?

[Geno]

It doesn't take long does it? After I had shut the PC down I thought to myself - did I just type 3000 when I meant 300? I had a liquid lunch\afternoon and was a bit riddled when I banged that out - apologies to all and thanks for advising me. Have corrected the wrong part of the post.