Trowel mastic on plastic beige vent on stone wall?

[Mr Whippy]

Just a quickie, is it ok to use trowel mastic (stone colour) on a beige plastic vent duct outlet to natural stone wall?

It’s a big gap due to uneven stone, about 2cm at points. I’m not sure silicone/stone caulk etc is a good idea as it’ll look rubbish without perfect application.

Also would be good to have easy removal in future if necessary for maintenance etc.


Just concerned about oil in the product and the plastic housing.

‘Twas only £10 so not a big issue if it melts or something.

[119]

Our fitter flattened off the stone so that it sat flatter.

There is is a small gap around the edge but he used colour match silicone and it’s been fine so far!

[Mr Whippy]

Yeah mine is ok on three sides, but the one facing the door is about 15-20mm deep, so it'd take quite some work to flatten.

I've used mastic for now and quite happy with the look. I just packed it under for some time, and then put a nice bevel over that to blend it all in.

I've been flip flopping on the best duct cover to use. Some are good for noise, but bad for letting colder air in, or vice versa... hopefully this one doesn't now react strangely due to the mastic sealing it up much more, as it's been quiet and operating normally for some months.

I'll post a pic later.