Mortar vs expanding foam vs bonding coat plaster vs deep filler?

[chrissy_a]

Whenever I've been faced with a deep gap or a hole, or exposed brickwork from crumbled plaster I've generally used either expanding foam/mortar/bonding coat to fill up to about the level of the wall and then used a light filler to level with the rest of the wall.

I'd previously been under the impression that the only fillers were the polyfilla type which were only really intended for small drill holes etc. However, I've recently discovered that you can get deeper fillers which will fill to pretty much any depth, it seems like a miracle and I've been questioning whether I ever really needed to use anything else.

I would like to be able to better understand which solution is better in which kind of situation so any advice would be much appreciated

 

[opps]

If I need to remove a metal electrical back box in a wall and sand it so that I can paint the wall the same day, I just use 2 pack (car filler). At that depth it is sandable in about 20-25 minutes.

However, if you have crumbly victorian plaster, the sanding required will rip the grit out of the adjoining plaster (2 pack filler is pretty hard). In such cases, I too use expanding foam- but in a gun as it is more controllable. I then fill with Toupret tx110 filler. It doesn't have depth limitations but if you used it to fill the whole of the box, it would take ages to dry.

Even with fillers such as TX110, a potential problem is that they will slump if used too deep in one hit. Yesterday I had to replace some missing render (20mm thick) from an exterior wall, I had to use plastering sand and cement.

I haven't use tubs of regular Polyfiller for years, I use powder based fillers that you add water to. I mix them in cut up, old plastic milk bottles and then bin the container after use.

Toupret TX110 is my go to because it cures quicker than their regular filler, but, on plaster where I only need to apply 1mm thickness, I use the regular Toupret interior. It is cheaper.

Another filler type that I use, but which is very soft is the lightweight "spackling" type. eg RedDevil Onetime. I like the fact that the dust generated when sanding doesn't become statically charged.

Other classes of fillers include epoxy resins- they are pretty expensive and normally used to deal with rotten exterior timber.

 

[chrissy_a]

Thanks for your reply. However, my question was more aimed at knowing if and when I should choose one of the other options instead of a filler.