Reply With QuoteHow have the gaps just ‘developed’? Looks like edge of rendering has been knocked off somehow.
Agree with your idea though - plus silicone sealant where it meets the frame.
The back of the house has developed some gaps around some of the exterior ground floor windows, mainly around 5mm in size. Obviously i need to sort this before winter and wondered the best way to tackle this and stop water getting in. I'm pretty handy with cement so could bond and cement the gap, paint over the top.
Are there any better ways of doing this material wise or other techniques that would be suitable? Thanks for any DIY knowledge!
Last edited by vulcangascompany; 9th August 2022 at 17:27.
How have the gaps just ‘developed’? Looks like edge of rendering has been knocked off somehow.
Agree with your idea though - plus silicone sealant where it meets the frame.
The edges of the render have become very crumbly due to weathering. The other areas i have patched previously had variable success, some bits have been fine some will need redoing. I probably did this 4/5 years ago. Just wondering whether theres a better material ‘filler’ than cement?
Expanding foam may be good to use to fill the gap.
You can then add cement etc to finish off. Maybe use an edge strip to keep it from crumbling again?
Maybe some kind of UPVC strip which is the same depth as the render. Try to affix it at 90 degrees to the window frame. Fill the resultant gap with expanding foam. Cut the foam back once it sets and render or plaster over up to the edge of the upvc strip.
How do you think that is going to work? I’ve learned (the hard way) that expanding foam can even bow a door casing because I neglected to brace it in the middle, so a thin upvc cover strip doesn’t stand a chance.Originally Posted by kungfupanda
I’d suggest first and foremost making good the render. A tube of exterior frame sealant will deal with the gap.
Expanding foam - use minimal amount.
Once dry, trim back the excess. Cement render to repair up to the window frame then run a thin bead of silicone between the edge of the render and the frame.
When you look long into an abyss, the abyss looks long into you.........
Expanding foam, then cut it back and render it. Use water proof masking tape to stay straight.
Thanks for all the suggestions guys, i think i'm going to try the exterior frame sealant to fill the gap first and render on top, with edge strips if needed.
Some low expansion foam 1st then rerender
You’re going to need something to cater for the expansion and contraction of the frame, I think. Google or YouTube as a first step?
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Same thought here. I will create a gap to straighten a door frame which is attached to a slightly curved lintel and will then fill it with low expansion "door and window" foam.
I also think you should create a small break gap between render and frame and cover this with a flexible sealant.
Is that pink plaster I can see or is it just the photo making it look pink?
If it is pink then as far as I know it’s not intended for outside and will absorb water so if it were me I’d personally be getting it chopped back and re-rendered.
I'd guess it's a weak sand/cement render rather than a skim coat.
It's likely that when the upvc window was installed the fitter then made up the render with a very weak mix to save money. They are often self employed working for some of the larger firms and cost of cement comes out of their pocket. So using a weak mix leaves more money for them.
Cut the weak render back and pva to ensure a good key, use frame fixing foam. Render with appropriate strength material.
Looks like a thin skim of sand and cement over what to me looks like pink plaster but as you’ve pointed could equally be weak mixture of red sand and cement.
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