System for placing structural posts

[AnerleyBoy]

In a TV building programme I saw a system for placing structural posts - to support a biggish veranda for a house, I think. They drilled a 1m hole with a motorised auger, put a large inverted plastic funnel in the hole, poured concrete into the funnel, pushed a steel post down into the concrete in the funnel and back-filled. Quick, accurate, stable and economical.

Structural post system

• AnerleyBoy
• 29 Sep 2013
• 1

An inverted plastic funnel is placed in a hole; concrete is poured into the funnel; a post is...

Has anyone else seen this? What do you call the plastic funnels and/or this system? Where can I get more information?

 

[noseall]

Whilst i admire the engineering and the effort they have put into resisting uplift, it would be considered excessive and a waste of time in most cases.

The reason being is that a majority of post supported structures will have a weakness elsewhere and would give before the concrete lifted out of the ground.

A standard hole dug in the ground combined with a post with a foot welded to the bottom and concreted in, will usually do.

 

[AnerleyBoy]

Good points, Noseall.

I think the builders would say that they're employing a system to achieve consistent quality while saving labour and concrete; they score budget points and eco points.

The auger is a substantial specialised machine but probably costs no more than a mini-digger, for example. A contractor would hire one for a day and a labourer would put in a dozen or more holes easily (in the right ground, of course).

The funnels are recycled plastic, no doubt - a bit like garden water-butts or compost bins.

The funnel gives a big footprint for stability and to resist subsidence while being economical in its use of concrete. It can easily be positioned very accurately before the concrete is poured; probably there are some clever jigs on the neck to ensure accurate centring of the post. In the case in point, I think that steel beams were to be bolted to the steel posts, so accurate positioning was very important.

I hadn't thought about uplift but the programme was probably made in Canada or the northeastern US, where frost heave must be a major concern.

Anyway, the question is still, Does anyone know what this system is called?

 

[noseall]

Are you fitting about 30+ verandas or is this a one off?

 

[tony1851]

The funnel gives a big footprint for stability and to resist subsidence while being economical in its use of concrete. called?

The funnel isn't economical in concrete, quite the reverse. The footprint could equally well be formed in a normal concrete pad. with some rebar sticking up. What matters is the connection between the base and whatever it is supporting.

 

[noseall]

What matters is the connection between the base and whatever it is supporting.

Yeah I think that was what I mentioned earlier..

 

[big-all]

The funnel gives a big footprint for stability and to resist subsidence while being economical in its use of concrete.

if you fill the funnel with concrete then fill the hole with concrete then you will use an identical amount off concrete minus the plastic volume and trapped air volume

 

[AnerleyBoy]

Thank you, everybody.

For the sake of argument:
(1) If the cube has Volume V then a cone of the same height and base width has volume V x (pi/12); that's roughly V/4. Of course that cube would have a bigger footprint by a factor of (4/pi) - about 25% bigger.

(2) When I said, "backfill" I meant "put back into the hole the stuff you've taken out" not "pour in more concrete".

(3) What is the ratio of the volumes of a cone and a cube that have equal footprints and height?

(4) I said earlier in the thread that in the example I saw on TV years ago I think the (steel) post was to be bolted to steel beams.

(5) Hands up if you've ever happily pointed out the flaws in a system or product - and found yourself using it all the time a little while later?

If only we knew the name of this system we could batter the manufacturer with these points - they've probably all been raised and answered. The manufacturer is/was trying to sell to builders, after all.

Now, puh-leeeez, back to the topic - which I should have titled "Do You Know What This System Is Called, However Useless You Might Think It ?"

 

[big-all]

yes that makes sense
although i tend to do it the other way like a mushroom
it would be interesting to know which gives better support

 

[Deluks]

I think I remember seeing this on Holmes on Homes, he kept banging on about sonotubes, essentially giant bog rolls!

 

[AnerleyBoy]

Thanks, Deluks. I've had a quick look at Sonotubes' website and it's interesting stuff but not what I'm talking about - unless it's elsewhere on their site.

I think the Big Upside-Down Funnel must have appeared on 'Holmes' or 'This Old House'. Bike Mike built a two-storey veranda/deck for a woman whose original construction had collapsed under her and her friends. He put in posts for the new one, of course.

 

[jerryhubbard]

They are called a big foot system and mainly used in Canada where they have heavy frosts.
The sonotube (large bog roll) is similar but doesn't have the large footprint at the bottom and are generally used for smaller projects.

 

[AnerleyBoy]

Well done, Jerry. Many thanks to all contributors.

Concrete post system

• AnerleyBoy
• 2 Oct 2013
• 1

Big Foot and Sonotube (or similar former)

My memory was faulty in several matters (big surprise!) -
the Big Foot is smaller and flatter than I remembered;
its neck is made to fit into a Sonotube or similar;
presumably post and foot are poured at the same time.