Dealing with large 15cm hole in fibrolite cladding

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neb

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#249341 6-May-2019 20:15

Here at the Casa de Cowboy a previous owner cut a ~15cm hole in the fibrolite cladding and then later tacked a piece of galvanised iron sheet over it to cover it. Needless to say this isn't the best solution in terms of waterproofing, and I'd like to apply a better fix. The obvious fix is the same approach as you'd use for gib (glue in backing boards, cut and glue fibrolite plug into the hole, patch with exterior-grade filler, sand, paint etc), but I since it's a 1970s house the fibrolite may contain asbestos so I'm not keen on cutting and sanding it too much.

The other alternative is just to glue a square patch over the top and seal the edges, leaving the original fibrolite alone, but that leaves an obvious patch in place.

A related problem is where to get a small amount of fibrolite for either the small plug or larger patch, without having to buy an entire board. I've tried the local Bunnings in case they have some offcuts somewhere but no luck.

Any ideas/suggestions?

eracode

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#2231945 6-May-2019 20:21

Depending on the thickness of the fibro (~ 5mm?) couldn’t you use something other than fibro - say 5 mm marine ply? And use that standard gib repair approach.

But I guess you still have the problem of where to source a small piece.

Why not back up the hole as per gib repair approach but then fill the hole with epoxy builders’ bog filler, sand/fill/finish and paint.

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neb

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#2231962 6-May-2019 20:46

eracode: Why not back up the hole as per gib repair approach but then fill the hole with epoxy builders’ bog filler, sand finish and paint.

I'd considered various types of filler, but the problem is getting a good even finish across a gap that large, glueing in a patch means there's at most a bit of unevenness around the edges where there's filler while using bog or equivalent means I need to get the entire lot level and smooth.

I'm not sure if there's a perfect solution, just looking for general ideas or suggestions... the marine ply idea might work, I've got some lying around somewhere but it's got a very rough surface so would need a fair bit of filler to get it smooth.

Gib is so much easier to deal with, patching the same hole on the inside wall was a breeze.

eracode

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#2231963 6-May-2019 20:50

neb:
eracode: Why not back up the hole as per gib repair approach but then fill the hole with epoxy builders’ bog filler, sand finish and paint.

I'd considered various types of filler, but the problem is getting a good even finish across a gap that large, glueing in a patch means there's at most a bit of unevenness around the edges where there's filler while using bog or equivalent means I need to get the entire lot level and smooth.

If you backed it up, filled with bog, screed across the whole thing with say a stainless steel rule, let cure then top up fill with acrylic filler if necessary, sand, paint - should come out ok.

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neb

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#2231967 6-May-2019 21:02

eracode: If you backed it up, filled with bog, screed across the whole thing with say a stainless steel rule, let cure then top up fill with acrylic filler if necessary, sand, paint - should come out ok.

Hmm, yeah, let me think about it, I still have a bit of bog from the windowsills. Another thought was plug it with expanding foam and patch over the top with bog, since I haven't got a lot of it left. Would also insulate that part of the wall while I'm at it.

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#2231968 6-May-2019 21:04

1970's fibrolite will almost certainly be asbestos so obviously take appropriate precautions around it.

neb

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#2231970 6-May-2019 21:07

sbiddle:
1970's fibrolite will almost certainly be asbestos so obviously take appropriate precautions around it.

Yeah, 3M respirator with particulate filters, and whatever approach involves the least sanding.

eracode

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#2231972 6-May-2019 21:12

neb:
eracode: If you backed it up, filled with bog, screed across the whole thing with say a stainless steel rule, let cure then top up fill with acrylic filler if necessary, sand, paint - should come out ok.

Hmm, yeah, let me think about it, I still have a bit of bog from the windowsills. Another thought was plug it with expanding foam and patch over the top with bog, since I haven't got a lot of it left. Would also insulate that part of the wall while I'm at it.

IMO expanding foam would be difficult to deal with on a job like this because it’s hard to control. Probably not the best product for the job. Sticky as sh@t and gets everywhere. You’ve only got 5-7 mm depth to fill and you can’t screed the foam.

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neb

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#2231979 6-May-2019 21:17

eracode: IMO expanding foam would be difficult to deal with on a job like this because it’s hard to control. Probably not the best product for the job. Sticky as sh@t and gets everywhere. You’ve only got 5-7 mm depth to fill and you can’t screed the foam.

Oh, I meant fill the wall cavity, shave off anything that sticks out, and lay bog over the top.

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#2232010 6-May-2019 21:45

The narrow sheets intended for soffits aren't expensive. I've used the gib patch model, piece glued (exterior pva)inside hole (after tracing shape of hole onto cardboard) cut another piece to match template and glue in hole. Then you just have 2-3mm ring around patch to fill with cement if you have some. If the patch is the same thickness as the original sheet there shouldn't need to be any sanding.

neb

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#2232033 6-May-2019 22:17

Something like Primaflex? Hmm, yeah, let me see if I can bludge a small scrap from Bunnings or M10 rather than buying an entire sheet and tossing most of it, the other option would be to get a 5mm Corflute sheet since I can reuse the rest as a work surface, downside is I'm not sure how paintable polypropylene is given how hard it is to glue it. I've got a tin of Lumbersider that I use for repairs on the rest of the house, so I'd need to prep the PP so the top coat will adhere properly. Hmm, and the sealant around the edges probably won't adhere well either.

Well, at least I've got a wishlist of materials I can ask the hardware places about, with a bit of luck they'll have one of the above. Until then, it's duct tape :-).

eracode

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#2232054 7-May-2019 04:20

Recommended best practice:

https://www.maintainingmyhome.org.nz/issues-and-repairs/issue/fibrecement-cladding-impact-damage/

Note the ‘wet sand’ - good idea under the circs.

Sometimes I just sit and think. Other times I just sit.