plasters affected by rain and DPC

[BauTomTom]

Hi People can you see this photo here?

somehow the palster starts to pill of approx in the line where the DPC was placed into the wall.

How can this be? what was wrong done?

Tom

 

[ishvaaag]

Whatever the leaflets say, dissimilar materials show their different nature at the hoints. The only way to get "nice" joints is to have them open and treated archiecturally or mechanically; in short, we all want our construction packages to be brought to the standards of say, car or plane-making. But a car costs say $6000/m3 where a building at purchase costs about $300. Where the costs to approach also would be approaching the levels of integration precisely at the joints that blemish our buildings; and even then would have to meet the issue of unicity for buildings against mass production for the cars.

Said otherwise, there is some degree of probability accepted by industry and regulations about that some thing at a building made according to the standing rules may not entirely work without any glitch. Some different detail of more cost might have not shown the problem at hand, but could then be neither in accord with the intent, will to pay, or aesthetic standards of the user.

 

[ishvaaag]

"hoints" ... that was a good one. Joints, of course.

 

[ishvaaag]

"Were the costs to approach ..." and other typographical errors, hum.

 

[Ron]

This appears to be a parge coating of plaster on masonry, extending over the floor slab edge.

The floor slab and the wall are expanding and contracting at different rates, thus the differential movement. As ishvaaag noted, there should be a defined joint at this location.

 

[BauTomTom]

ja the landscape is a problem as well but you guys says that at the DPC should be also a plaster joint provided?

ok what Ron says make also sense that the surfacebed and the wall behaves differently so do you provide there everytime a plaster joint?

it seams for me that the weet ground is weeting the wall and the watter goes up to the PCD and comes out there.

It seams I should rather provide a drainage or a slooping apron or something like this

Tom

 

[ishvaaag]

Certainly an application of a thin layer of some material across the boundaries of two different elements is prone to show aleatory cracks, even if as small as hairline cracks. This is simply a requirement of compatibility of deformations, that being different to both sides of the line, need be restored, and this is usually made by the appearance of a crack, since many times the necks at the joint or weakened support there make impossible to just keep the things going well with just locked stresses. The stresses build up beyond limit strength, and cracks appear.

 

[Ron]

As moisture is absorbed from the ground, the floor slab expands slightly. If the wall is relatively dry, it does not expand at the same rate, therefore you have differential movement, and thus, a crack.

When the wall absorbs water, but the slab does not, you have the opposite condition with the same result.

If water is bleeding from the crack, it is likely coming from an accumulation of moisture in the hollow cells of the masonry and weeping out at the crack. If this is the case, you will likely see some "efflorescence" or calcium-laden deposits at the crack.

 

[BauTomTom]

Thanks for the explantions. I see the problem

but only that I never noticed a joint in the plaster between the surfacebed and the walls. This is strange

I think to fix this problem now I will try to convince the client to provide an apron around the wall or a drainage pipe and gravel above to collect the water and take away from the building.

Tom

 

[onlineeng]

Are the walls block or frame?