Concrete stumps cracks

[Enhineyero]

Anyone have lots of expierence with un-reinforced concrete stumps? Inspected a house that have a cracked internal concrete stumps (100mm x 100mm) height of stump is no more than 1m. Loads are relatively small that an equivalent 100x100 hardwood post would work.

 

[Trippelsewe]

100mmx100mm x 1000mm high is very slender unreinforced. Are those dims correct?

 

[MotorCity]

Maybe this terminology is a regional thing, but what exactly is a concrete "stump"?

 

[dhengr]

MotorCity:
Concrete stumps..., I suppose they kinda grow (stand) up 1m out of the ground, kinda like a tree stump. Except, the tree stump has some roots to give it some lateral stability and uplift resistance, and its material fibers run in a direction which gives it some canti. bending resistance above grade. At 100mm by 100mm and canti. up out of the ground by 1m, this sounds like supporting the building on some toothpicks, and hoping for the best. Since these conc. posts are unreinforced, you would want to be careful in handling them, so you didn’t break them in the middle while installing them. There is no mention of how they are embedded, supported at grade, any footing, connection details at floor framing, or bracing, etc. The existing posts cracked because they saw a little lateral loading or may have started cracking during installation. I’ve seen worse, when people used 6' or 8' long 4x4 wooden posts stuck in the ground a couple feet. They stood there during construction, as long as nobody leaned on them.

 

[LittleInch]

Many of the hits seem to be Australian.

Like this one

http://buildinspectaustralia.com.au...nspection-frankston-fretting-concrete-stumps/

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Tomfh]

Unreinforced 100mm x 100mm stumps? That’s weird. They normally have a central bar. See pic.

How are these ones cracked?

 

[hokie66]

Yes, the terminology is uniquely Australian. 'Stumps' can be either concrete or timber, occasionally steel. If masonry, they are usually called piers. It just means a short column. For concrete, they were once cast in place, now invariably precast as in Tomfh's picture. 100 x 100 is too small, most are at least 150 x 150.

 

[Enhineyero]

Unreinforced 100mm x 100mm stumps? That’s weird. They normally have a central bar. See pic.

There is a central dia 6 bar.

Yes, the terminology is uniquely Australian. 'Stumps' can be either concrete or timber, occasionally steel

Wasn't sure if they had the same terminology in America and hoped that engineers from AU/NZ will respond. Luckily you did.

Are th

100 x 100 is too small, most are at least 150 x 150.

I work in a non-cyclonic area and 100x100 stumps are pretty common.

 

[hokie66]

What is orientation of the cracks? I have seen many concrete stumps which have split (cracked vertically) due to corrosion of the reinforcement.

 

[Enhineyero]

What is orientation of the cracks? I have seen many concrete stumps which have split (cracked vertically) due to corrosion of the reinforcement.

Vertical/slightly diagonal. I'm guessing the same. However, I thought these rods are galvanised. Is it likely galvanising got damaged during construction/transport? How do you avoid this from happening? applying cold gal to the bar prior to placing bearers?

 

[hokie66]

Not necessary to galvanise reinforcement when the environment is not aggressive, which you would not expect under most houses. Has there been flooding at some stage under the house?

The problem is with the concrete. Likely poor mix design, not enough cement, too much mixing water. Do you know how these were made? If cast in place, that would have required a very soupy, poor quality mix.

Restumping of houses is an industry in itself in parts of Australia. Just be sure to use precast stumps as in Tomfh's post above, as the concrete is of high quality.

 

[Enhineyero]

Restumping of houses is an industry in itself in parts of Australia. Just be sure to use precast stumps as in Tomfh's post above, as the concrete is of high quality.

I believe its precast, its smooth and markings of the fabricator can be seen. There might have been some flooding but not high enough to reach the underside of bearers.