External filler for render and window sill

[Martin Pentreath]

Hi,

I'm planning to do a bit of exterior redecoration. We have a bay window whi= ch is a triumph of the victorian cowboys who built this place. Its foundati= ons are (I think) two courses of bricks sitting on nice London clay. Conseq= uently it's not very stable. The last time it cracked up it was shored up u= sing helical bars. They're better than nothing, but there is still some mov= ement, and things have cracked up a bit since the last repaint (about six y= ears ago).

Anyway, as the options seem to be either underpinning it, or just filling t= he cracks every few years, I'm opting for the second. So the question is wh= at's the best thing/technique to use to fill it. Here are two photos:

shows the cracked rendered plinth. The other one shows a crack in the s= ill - it sounds pretty hollow underneath and I suspect when I give it a wh= ack a large chunk of it will fall away leaving a big hole.

Cheers!

Martin

[Ian Jackson]

In message , Martin Pentreath writes

How old is the house? If it's been there a long time, and there's no sign that anything will collapse, I would be tempted to repair things with something flexible, so at least the cracks won't reappear (or at least so they will only appear at the junction of the flexible and non-flexible parts - so you will know where they are).

[Martin Pentreath]

Hi Ian,

The house was built around 1880. But anyway, there aren't any structural pr= oblems with the rest of it - it's just the bay window that has no foundatio= ns. So really I'd already decided that it's just a filler job. I'm wonderin= g what the best filler is to use for this, and particularly for the sill, w= hich I think will be left with a gaping hole after I've removed the bit tha= t's cracked away.

[Ian Jackson]

In message , Martin Pentreath writes

Having done, in the past, a fair number of body repairs on my ever-rusting bangers, I'd be tempted to use up some of my car repair materials (fibreglass matting, resin and paste). I suppose 'Plastic Padding' is maybe the most appropriate (especially the flexible type). However, there are probably better 'genuine' building materials for the job - which others will advise on.

[The Natural Philosopher]

One thing I discovered about 'genuine building materials' is that they have only one overriding advantage. They are cheap.

One would be far better off with - say - a house made of GRP lined with PU foam, and self colored gel coat on the outside, than rendered. Especially if it were epoxy and not polyester. Bolts would be better than nails.

Beams of Titanium would be far better than wood. etc.

I leave you to draw the obvious conclusions.

[stuart noble]

Nothing better than car body filler IME, preferably a cheap 3.5 litre job from a trade outlet. £15 ish IIRC