dry-packing when underpinning
dry-packing when underpinning
(OP)
The general wisdom when dry packing, seems to be to have a 3-4" gap between the top of the old concrete and top of the old wall, is there a compelling reason you cant go thinner - say 2 inches?
If you trench under the wall on both sides, is it possible to ram the cement in from both sides and get a dense enough fill, or would I need to block up one side (eg with a stack of bricks) to ram against?
Thanks for any tips!
If you trench under the wall on both sides, is it possible to ram the cement in from both sides and get a dense enough fill, or would I need to block up one side (eg with a stack of bricks) to ram against?
Thanks for any tips!






RE: dry-packing when underpinning
RE: dry-packing when underpinning
Good luck!
Please remember: we're not all guys!
RE: dry-packing when underpinning
"It is imperative Cunth doesn't get his hands on those codes."
RE: dry-packing when underpinning
Yes it looks like non-shrink grout is widely available here in the uk as a dry powder.
http://gbr.sika.com/dms/getdocument.get/60789a95-d...
I was at first quite keen on this solution, but the detail looks problematic -
it says it should be applied in formwork with some pour hopper arrangement to give 150-200mm grout head
(so does that also mean you need some type of vibrator to ensure it flows into all the corners?)
Or is that overkill & it could be applied with a mortar gun?
It also says the surfaces should be blast cleaned and wetted for 6 hours before use. I'm not keen on using that quantity of water around the foundations during underpinning, since the structural settlement I'm fixing is likely in part due to a leaky drain and soft soil.
I would normally go over suraces with a wire brush & spray lightly with water a few times with a pump action sprayer, which with the low ambient temperature here is enough for bricks to stay damp for hours if not days.
RE: dry-packing when underpinning
RE: dry-packing when underpinning
www.eng-tips.com/viewthread.cfm?qid=232821
I have some experience pushing cement into joints from Helifix installation (www.helifix.co.uk)
I think I'll need to put a form on one side of the wall to pack against, I guess shuttering ply or similar screwed to the wall is going to be more secure than messing about with a heavy stack of bricks.
RE: dry-packing when underpinning
RE: dry-packing when underpinning
I won't have any objections to a thinner layer if the in situ conditions allowed for it.
RE: dry-packing when underpinning
One key is to scrub or pressure wash the underside of the existing concrete before setting the forms for the underpinning footing, when you have room to do this, to dislodge soil.
3-4" clearance might make the job more comfortable, but if the grout mix isn't at perfect moisture content (i.e. at all too wet) you will get a poor result. Working with the dry packing mix was not easy for an amateur, and I can imagine the temptation to do the work wrong would be very tough to resist if you were being paid by the job.