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Joining new concrete to old



 
 
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  #1  
Old August 10th 06, 05:11 PM posted to uk.d-i-y
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Default Joining new concrete to old

I'm adding a shed on the side of my garage.

It works out that the new concrete floor level will just nicely line up
with the top of one of the existing concrete steps into the garage -
makes a nice reference point for the levelling.

However the existing step has quite a 45 deg. bevel on it's leading
edge. Do I need to treat this in any way to get the new concrete to
bond to it ? My concern is that if the bond isn't reasonable, the new
concrete will break away in time as it is potentially a weak spot.

Thanks

Rob

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  #2  
Old August 10th 06, 05:17 PM posted to uk.d-i-y
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Posts: 9,056
Default Joining new concrete to old

robgraham wrote:
I'm adding a shed on the side of my garage.

It works out that the new concrete floor level will just nicely line up
with the top of one of the existing concrete steps into the garage -
makes a nice reference point for the levelling.

However the existing step has quite a 45 deg. bevel on it's leading
edge. Do I need to treat this in any way to get the new concrete to
bond to it ? My concern is that if the bond isn't reasonable, the new
concrete will break away in time as it is potentially a weak spot.

Thanks

Rob

Its never a bad idea to chisel some slots and install some sort of metal
ties in.
  #3  
Old August 10th 06, 08:48 PM posted to uk.d-i-y
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Posts: 3,017
Default Joining new concrete to old

robgraham wrote:
I'm adding a shed on the side of my garage.

It works out that the new concrete floor level will just nicely line
up with the top of one of the existing concrete steps into the garage
- makes a nice reference point for the levelling.

However the existing step has quite a 45 deg. bevel on it's leading
edge. Do I need to treat this in any way to get the new concrete to
bond to it ? My concern is that if the bond isn't reasonable, the new
concrete will break away in time as it is potentially a weak spot.


A 45 degree bevel on a step? - are you sure it's not just a kerbstone laid
flat on it's back?
Either way, you can't 'chamfer' concrete in this way, you are right to
assume that it will crack up, the only way to stop this is to give it more
depth, IE cut out a straight line with a grinder and chisel off an inch or
two in depth, treat with neat PVA prior to concreting and scrape some slop
into it.


  #4  
Old August 10th 06, 10:36 PM posted to uk.d-i-y
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Posts: 1,682
Default Joining new concrete to old


Phil L wrote:

A 45 degree bevel on a step? - are you sure it's not just a kerbstone laid
flat on it's back?
Either way, you can't 'chamfer' concrete in this way, you are right to
assume that it will crack up, the only way to stop this is to give it more
depth, IE cut out a straight line with a grinder and chisel off an inch or
two in depth, treat with neat PVA prior to concreting and scrape some slop
into it.


Yes a chamfer would have been a better word; when I cast the steps some
25 years ago I obviously put a chamfer on the leading edges so that
they wouldn't chip. OK I'll now have to cut it out !! Thanks for the
advise.

Rob

  #5  
Old August 10th 06, 11:57 PM posted to uk.d-i-y
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Posts: 1
Default Joining new concrete to old

I did something similar 10 years ago.....

Footings to my garage are a metre wider than the garage (raft foundation).
My new block built shed was to be roughly 8' wide so needed footings that
reached beyond the scope of the garage foundations.
I got two great lengths of angle iron, bent them into large V shaps and
bolted them to the side of the footings.
Then I poured the concrete - angle iron was then submerged in concrete.
OK, no 45 degree thing going on, but that new groundwork has never moved a
milimeter in 10 years.

Hope that helps

Regards
Paul



"The Natural Philosopher" wrote in message
...
robgraham wrote:
I'm adding a shed on the side of my garage.

It works out that the new concrete floor level will just nicely line up
with the top of one of the existing concrete steps into the garage -
makes a nice reference point for the levelling.

However the existing step has quite a 45 deg. bevel on it's leading
edge. Do I need to treat this in any way to get the new concrete to
bond to it ? My concern is that if the bond isn't reasonable, the new
concrete will break away in time as it is potentially a weak spot.

Thanks

Rob

Its never a bad idea to chisel some slots and install some sort of metal
ties in.



 




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