Flaking roughcast

S

solway

Active Member
Hi all. Did a school last year and got a call today from builder who says roughcast is "crumbling" under wall copings on a boundary wall we did. I called to investigate and it seems 6 to 8 inches under the copings has gone crumbly/ flaky. The rest of the wall below the 6 to 8 inches is solid. The copings are 900mm in length and theres probably 10 per panel. The joints in the copings are probably 3-5mm wide and are not sealed plus theres no dpc between the copings and top of the blockwork which is 9 inch cavity block. It seems like frost damage...... Water getting in between coping joints, spreading and lodging. The opposite side of the wall is also roughcast but there is no sign of the problem on this side. Any thoughts as to what is going on here????
 
solway said:
Hi all. Did a school last year and got a call today from builder who says roughcast is "crumbling" under wall copings on a boundary wall we did. I called to investigate and it seems 6 to 8 inches under the copings has gone crumbly/ flaky. The rest of the wall below the 6 to 8 inches is solid. The copings are 900mm in length and theres probably 10 per panel. The joints in the copings are probably 3-5mm wide and are not sealed plus theres no dpc between the copings and top of the blockwork which is 9 inch cavity block. It seems like frost damage...... Water getting in between coping joints, spreading and lodging. The opposite side of the wall is also roughcast but there is no sign of the problem on this side. Any thoughts as to what is going on here????
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Basically what you said water ingress through coping and freezing
 
check copings have a drip
, wind side blowing rain runoff back on wind side
 
West facing panel. Overhang about 30mm. Drip is underneath but about 5mm off the render. Theres 4 panels and 2 seem affected. Strange how below the 6-8 inches it's not affected at all. There is definitely a sheltered element to the opposite side. Green algae is pretty bad on the copings and running onto the top 6-8 inches(affected bit)
 
solway said:
West facing panel. Overhang about 30mm. Drip is underneath but about 5mm off the render. Theres 4 panels and 2 seem affected. Strange how below the 6-8 inches it's not affected at all. There is definitely a sheltered element to the opposite side. Green algae is pretty bad on the copings and running onto the top 6-8 inches(affected bit)
Click to expand...
A light breeze would take the water from drip to render joint , 5mm don't sound good
 
solway said:
Hi all. Did a school last year and got a call today from builder who says roughcast is "crumbling" under wall copings on a boundary wall we did. I called to investigate and it seems 6 to 8 inches under the copings has gone crumbly/ flaky. The rest of the wall below the 6 to 8 inches is solid. The copings are 900mm in length and theres probably 10 per panel. The joints in the copings are probably 3-5mm wide and are not sealed plus theres no dpc between the copings and top of the blockwork which is 9 inch cavity block. It seems like frost damage...... Water getting in between coping joints, spreading and lodging. The opposite side of the wall is also roughcast but there is no sign of the problem on this side. Any thoughts as to what is going on here????
Click to expand...
Did this builder put the copings on?
 
Have another look after a heavy rain and look for damp patches.

i noticed the same problem earlier this week on a neighbouring property. The coping looked substantial but 4 dipped slightly causing the monocouche to crumble on the surface.
 
solway said:
Hi all. Did a school last year and got a call today from builder who says roughcast is "crumbling" under wall copings on a boundary wall we did. I called to investigate and it seems 6 to 8 inches under the copings has gone crumbly/ flaky. The rest of the wall below the 6 to 8 inches is solid. The copings are 900mm in length and theres probably 10 per panel. The joints in the copings are probably 3-5mm wide and are not sealed plus theres no dpc between the copings and top of the blockwork which is 9 inch cavity block. It seems like frost damage...... Water getting in between coping joints, spreading and lodging. The opposite side of the wall is also roughcast but there is no sign of the problem on this side. Any thoughts as to what is going on here????
Click to expand...
think u have answered it yourself coping slight tilt on them as well that's why its a one sided thing
 
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