Why cast with cardboard tubes?

[pbol]

Hello,

Maybe a dumb question, but a common way to cast footings seems to be with paper tubes. But what function does the tube serve? The paper will decompose and leave a space?

/peter

 

[Fotografen]

The tube's task is to hold the concrete until it has set. I suspect the reason the tubes are made of cardboard is that they are easy to cut and handle otherwise.

 

[skutten11]

As the Photographer says
Cardboard tubes are used for footings during casting and can remain in place or be removed; rotting and leaving space is not something accounted for, but anything can be used for formwork, building yourself with wood, large sewer pipes, spiral pipes, etc.

 

[pbol]

As the Photographer says
Paper tubes are used for concrete pillars and can be left in place or removed, the idea of them rotting and leaving space is not something that's considered, but you can use anything for the form, build it yourself with wood, large sewer pipes, spiral pipes, etc.

I'm mostly thinking that if you want a maximally stable pillar, you drill a round hole and pour concrete directly into the hole. Thus, you achieve maximum stability against the ground because you're casting against solid ground that hasn't been dug up, nor pipes that rot away. If you're going to dig a big hole anyway, you might as well place a ready-made pillar.

 

[Daniel 109]

If the terrain makes it possible, then it's probably not a bad idea. In practice, it likely doesn't work in very many places.

 

[ceson]

I only do that now, drill and cast directly in the hole.

 

[kurt]

But often you should also cast the foundation a bit above the ground, if nothing else, it is very practical if you want to ensure that all foundations are at the same level.

 

[Plupp 173289]

Exactly. The pipe doesn't need to go all the way down to the bottom of the hole if it stands steadily.

 

[Maestrof]

I mostly think that if you want a maximally stable pier, you drill a round hole and pour concrete directly into the hole. Thus, maximum stability against the ground because you're casting against firm ground that hasn't been dug up, nor any pipe that could rot away. If you're going to dig a large hole anyway, you might as well place a ready-made pier in it.

From what I have read and learned, it seems to primarily be about reducing the amount of concrete you use. With a pipe, you know it will be a pier where all the concrete is joined together securely. If you cast directly in the ground, there will likely be some narrower parts of concrete that don't provide any support. At the same time, the pier is shaped according to the hole, and as you say, it should provide more support.

 

[droopy]

I mostly think that if you want a maximally stable foundation pier, you drill a round hole and pour concrete directly into the hole. This provides maximum stability against the ground because you cast against solid ground that is not dug up and not a tube that might rot away. If you're going to dig a big hole anyway, you might as well place a ready-made pier down there.

When casting piers for more serious purposes such as house foundations, the piers should be reinforced and ideally also rest on a "slab." For example, I cast 12 piers where the bottom is a slab 500x500 mesh-reinforced with 4 pieces of 8mm iron upwards in the tube, which was 1200mm long (dug down to 1400 and bedded with single plus tamp the single.

This was on ground that was not frost-susceptible (sand and gravel). But the extension hasn't settled even a mm.

When drilling a hole and filling it, it's also difficult to get rid of any air bubbles in the concrete. I was admittedly a bit over-ambitious when I happened to borrow a small vibrator that fit in the tubes, so the piers were also "nice" and smooth without any bubbles. Pleasant for the part that is visible above ground.

 

[Workingclasshero]

I mostly think that if you want a maximally stable post base, you drill a round hole and pour concrete directly into it. This provides maximum stability against the ground because you're casting against solid ground that hasn't been dug up, and there's no pipe that will rot away. If you already have to dig a large hole, you might as well place a ready-made post base in it.

If possible, you just dig a hole and cast in it, the problems are that it requires more concrete and you can't cast higher than ground level. In several places, I've lowered pre-cast post bases, super convenient, but they don't end up frost-free......Papprör can be placed exactly where you want and at exactly the right height.