Structural Engineers Impart Their Wisdom On Vorb

Postby Sims on Tue 4/Aug/15 10:39am

Any structural engineers out there?

Sometime in the 1970ites, the previous owners dug in against the side of the house to install a carport. Concrete was poured against the cutting in order to support the soil and brick footings. A reinforced concrete pad was poured at the base for parking. The poured concrete retaining wall only sits 100~150mm deeper than the concrete pad.

Given how shallow the base of the concrete retaining wall is, do you think that the concrete pad contributes to its strength? Because I'd quite like to remove the concrete pad in order to reset the level on the drive to a single continuous slope.

Thoughts?
pooZ8X3CIzVZhtghm5xVZVJu89pEiv5rxvi4qhMz7WQ.jpeg
Sims
Member for: 15 years 2 months

Re: Structural Engineers Impart Their Wisdom On Vorb

Postby Dougal on Tue 4/Aug/15 11:36am

Do you want to know how dodgy it is or how dodgy it'll become?

I'm not structural, but I think due to the static ground pressure (worse when wet) behind that concrete that it's already dodgy and would need support. I'd be approaching a Structural Engineer for a pile design to hold up that concrete wall and then you can do what you want (within reason) to the driveway beside it.
Dougal
Member for: 14 years 5 months

Re: Structural Engineers Impart Their Wisdom On Vorb

Postby Sims on Tue 4/Aug/15 12:03pm

Dougal wrote:Do you want to know how dodgy it is or how dodgy it'll become?

I'm not structural, but I think due to the static ground pressure (worse when wet) behind that concrete that it's already dodgy and would need support. I'd be approaching a Structural Engineer for a pile design to hold up that concrete wall and then you can do what you want (within reason) to the driveway beside it.


Yes I was thinking it was dodgy. Thankfully that side of the house doesn't get wet. Redoing that wall would at least get rid of the ugly step along the top.

Smells like $$$
Sims
Member for: 15 years 2 months

Re: Structural Engineers Impart Their Wisdom On Vorb

Postby Dougal on Tue 4/Aug/15 12:06pm

Is that brick work a ring foundation?
Dougal
Member for: 14 years 5 months

Re: Structural Engineers Impart Their Wisdom On Vorb

Postby philstar on Tue 4/Aug/15 12:07pm

the concrete that is there will contribute to the structural integrity of the wall, particularly stopping the base of the wall moving out.

are you planning on making the ramp significantly longer? or just smoothing out the ramp that is there?
philstar
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"misanthropic"
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Re: Structural Engineers Impart Their Wisdom On Vorb

Postby gristle on Tue 4/Aug/15 12:33pm

Does the concrete wall have a footing/toe that extends out under the pad?
Not an engineer, but have seen some things when renovating that make you scratch your head (brick walls, no footing...)
gristle
Member for: 10 years 11 months

Re: Structural Engineers Impart Their Wisdom On Vorb

Postby Sims on Tue 4/Aug/15 1:50pm

Dougal wrote:Is that brick work a ring foundation?

Correct - the house is timber piled through out. The height of the earth under the house, roughly follows the base of the red brick work.


philstar wrote:the concrete that is there will contribute to the structural integrity of the wall, particularly stopping the base of the wall moving out.

are you planning on making the ramp significantly longer? or just smoothing out the ramp that is there?

I'd like to get rid of the flat bit, so its just one smooth continuous slope down from the upper concrete part. In other words, I'd be adding fill to build up the back part of the flat pad.


gristle wrote:Does the concrete wall have a footing/toe that extends out under the pad?
Not an engineer, but have seen some things when renovating that make you scratch your head (brick walls, no footing...)

Nope there's no toe. Its just kinda leaning up against the house. :cry:
Sims
Member for: 15 years 2 months

Re: Structural Engineers Impart Their Wisdom On Vorb

Postby philstar on Tue 4/Aug/15 2:33pm

Sims wrote:
philstar wrote:the concrete that is there will contribute to the structural integrity of the wall, particularly stopping the base of the wall moving out.
are you planning on making the ramp significantly longer? or just smoothing out the ramp that is there?

I'd like to get rid of the flat bit, so its just one smooth continuous slope down from the upper concrete part. In other words, I'd be adding fill to build up the back part of the flat pad.


like so?
download-147818-480v .jpg


if that is the case you may be able to leave some (or maybe all) of the concrete pad there. just depends on how dodge you want to be, but you will be in a better position than it is now with the extra fill if you make the new retaining wall (on the near side of the photo) properly.
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"misanthropic"
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Re: Structural Engineers Impart Their Wisdom On Vorb

Postby Sims on Tue 4/Aug/15 2:42pm

Correct

I could potentially pour a small tongue at the base of the wall, and tie it back in with structural steel. Once that was sitting under a half meter of fill it would add a fair bit of strength. The top of the concrete tongue could form the curb for the new driveway level.
Sims
Member for: 15 years 2 months

Re: Structural Engineers Impart Their Wisdom On Vorb

Postby Dougal on Tue 4/Aug/15 2:50pm

Sims wrote:Correct

I could potentially pour a small tongue at the base of the wall, and tie it back in with structural steel. Once that was sitting under a half meter of fill it would add a fair bit of strength. The top of the concrete tongue could form the curb for the new driveway level.


That's basically undoing the original dodginess.
Dougal
Member for: 14 years 5 months

Re: Structural Engineers Impart Their Wisdom On Vorb

Postby philstar on Tue 4/Aug/15 2:51pm

Sims wrote:Correct

I could potentially pour a small tongue at the base of the wall, and tie it back in with structural steel. Once that was sitting under a half meter of fill it would add a fair bit of strength. The top of the concrete tongue could form the curb for the new driveway level.


where you need the most strength is at the end of the wall (bottom of the ramp)
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"misanthropic"
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Re: Structural Engineers Impart Their Wisdom On Vorb

Postby Sims on Tue 4/Aug/15 3:01pm

Dougal wrote:
Sims wrote:Correct

I could potentially pour a small tongue at the base of the wall, and tie it back in with structural steel. Once that was sitting under a half meter of fill it would add a fair bit of strength. The top of the concrete tongue could form the curb for the new driveway level.


That's basically undoing the original dodginess.


We're getting there slowly... Wiring dodgyness has been fixed (TRS wiring in the roof :cry: ), drainage dodgyness has been fixed (stormwater went into mystery drain that dead-ended)... Now starting to think about this side of the house.
Sims
Member for: 15 years 2 months

Re: Structural Engineers Impart Their Wisdom On Vorb

Postby gristle on Tue 4/Aug/15 3:14pm

You could also put a timber retaining wall offset from the house by approx 400-500mm, roughly following new drive gradient. Drainage behind and metal backfill. Means you don't weaken existing wall while building. Will need to punch holes through existing drive for posts.
gristle
Member for: 10 years 11 months

Re: Structural Engineers Impart Their Wisdom On Vorb

Postby KieranC on Tue 4/Aug/15 7:11pm

have a look at this https://en.wikipedia.org/wiki/Retaining ... nction.jpg

One good tieback anchor in the middle should be enough to hold it back, the walls I've helped build only had 1 good anchor to each 5m section for a 1.5-2.5m high wall x 400-500mm deep concrete/rock (so had heaps of weight to keep it down too)

if you drill through the retaining wall and stick a galv/SS treaded rod through with a decent size washer to spread the load and attach an anchor of your choice to the under house side. You might be able to incorporate it into the house pilings, rather than digging in and concteting a T shape anchor or similar.

However if it hasn't moved in the last 30-40 years what are the chances of it going in the next 40? any signs of stress?




im not a qualified BTW
:baaa:
KieranC
Member for: 10 years 11 months

Re: Structural Engineers Impart Their Wisdom On Vorb

Postby happybaboon on Wed 5/Aug/15 3:08am

Ball peen on it as hard as you can for twenty minutes. If your house doesn't fall down in the month afterwards it's sweet as.
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