upvc fitted windows into a rendered building

Postby pendlewitch » Mon Aug 20, 2007 3:08 pm

Please can anyone help me to solve a problem. I had upvc windows fitted about 3 years ago, and the cement broke away at the bottom corners where the windows meet the wall rendering. the builder came back three times, but the porblem recurred. I have now got another builder to repair the damage, but he has been back several times and the same thing is happening.
The new builder has also fitted a new upvc patio door frame and replaced the rendered edge with pebbledashing like the previous upvc and aluminium frame. One side of that rendering has also cracked off at the bottom corner.
The house faces south and has open land at the back, so is open to extremes of weather - hot sun and driving rain etc.
The builder has tried different mixes of concrete and has used plastisers and finished off with plastic sealant between the frame and the rendering, but still comes across the same problem.
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Simply Build It

Postby immo » Mon Sep 03, 2007 2:37 pm

Research different methods and email some building merchants.
I think the builder needs to seal the old render/brickwork first before he applies the new render. -So it sticks better.

When making the render he should use a pva mixture with it to help it bond and stick also.
Use correct colour sand with a bit more cement, maybe 10 sand to 4 cement.

If it is in constant wethering then use a shelter from start up until about 1 or 2 weeks after. The pebble dash probably weighs it down also.

I would apply it in stages also, like a 5 mm skin then wait few days and gradually build up until it comes to the pebble dash stage.
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