View Full Version : Engineer specified pad footing where I have existing strip footing
14th Feb 2012, 04:22 PM
I'm doing a two story house extension as owner builder. Just got the engineering docs back. The existing strip footing for internal brick walls is only 300x300mm and not strong enough to support the top storey. As a result I need to add "pad" footings as per the engineers calculations (approx 500mmx500mm).
Question - how do I do this where I have strip footing in the way? Do I just encase the old/ existing footing. Digging around the strip footing is going to be a right pain. And how do i add the reo? And which trade to I get to do this? Concreter?
Thanks in advance
14th Feb 2012, 10:57 PM
So the engineer has not provide drawings? As to the trade - a builder . . . :(
16th Feb 2012, 10:29 PM
my house is on 300W by 200 deep strip footings and with where I have excavated under the engaged piers 400 deep supporting 2 stories for over 50 yrs, looks like they dont make concrete like they use to. Up the road the new ext the engineer only specified 350x350 edge beams, so you must have reactive soil/clay
19th Feb 2012, 11:14 PM
Hi bloss. Yes, the engineer did provide drawings but now instructions :)
I can see what type of pad footing and where, but wondering how to retrofit the existing strip footing.
Regarding your response re trade... I'm doing the extension as an owner builder so your suggestion doesnt help me. A couple of builders I know are basically project managers. They used to be tradies (carpenters) but dont pick up tools these days - they will just sub out the work. I was asking for confirmation re which tradies they might use.
19th Feb 2012, 11:16 PM
Soil is clay/ reactive. Class M. I've noticed some cracks in some of the original internal and also external walls (these are double brickl!!)
1st Mar 2012, 11:01 PM
Still looking for advice/ instruction as to how I install 4 steel posts in a solid brick internal wall where existing strip footing 300x300 is not deep or wide enough (need to be at least 500x500). Do I cut the wall/ bricks and finish flush. Or should I just position the steel post close as possible to wall and have it visible. And then what about the pad footing? Can I just dig around existing strip footing and below it to make it 500x500x500?
1st Mar 2012, 11:33 PM
your engineer is the only person to give you this advice I am afraid to say.
3rd Mar 2012, 06:29 PM
26th Apr 2012, 12:20 AM
Thanks for the response. After a discussions with the structural engineer, he issued revised drawings. The steel posts are basically bolted to the existing brick wall and supported on the existing concrete strip footing. However, in addition I need to add a pad footing below the existing strip footing.
Now I wonder, how am I going to dig the hole for pad footing below the existing strip footing. The stip footing is about 300mmx300mm and 200mm below ground level. So I have to escavate approx 500x500x500 below this. How do I do that? I guess I'll ask the escavator however was wondering
26th Apr 2012, 09:09 AM
i'd probably consider using a sucker truck... less chance of damaging your existing walls and footings with a sucker truck.
hope this helps!
28th Apr 2012, 04:25 PM
Discussed with a builder friend. He suggested excavating both sides of the existing strip footing (about 450w x 600 long x 600deep). Drill and inserting steel rod into existing footing. Then pouring concrete down both sides. thus no need to try escavate under the existing footing. This looks and sounds much simpler. Will run it past the engineer and get him to confirm if OK.
28th Apr 2012, 11:00 PM
to the last post, sounds good in theory, but in reality you wont get a rotary hammer drill & bit into a narrow trench to drill the holes, plus the bars will have to be anchored into the existing concrete somehow & be tested for withdrawal strength or use a system with a known strength.
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