Filling a void behind plasterboard

[Stones]

I have a smallish void behind plasterboard to fill.  Expanding foam is the ideal product, but I really don't want to have to do more than drill a small hole or two into the plasterboard - cutting a large hole out of the plasterboard and repairing thereafter is not an acceptable option.

 

I know the volume, dimensions and shape of the void.

 

My thoughts are to drill two, perhaps three holes to cover the length of the void (600mm) positioning them such that I could angle the nozzle of the foam gun extension through an arc to get the best coverage. This would also in part ensure there was somewhere for displaced air to go.

 

As I see it the main issues are going to be judging how much foam to squirt in (as I don't want over expansion blowing the plasterboard off) and ensuring a good cure given most expanding foams are moisture curing.

 

I'm thinking it may be worth buying a USB inspection camera scope that I can plug into my phone so I can at least get some idea of what's going on in the void and to assist in curing, use a plant mister to spray in a little water into the void before applying foam.

 

Any other suggestions?

[Russell griffiths]

If you use the new soudal foam, there is no expansion. 

Have a look at their new catalogue, some good new products 

[Stones]

Certainly Soudal is the main brand stocked locally.  WIll check it out.

[PeterW]

A row of 8mm holes up the wall will allow you to inject foam and it will spread pretty evenly - excess will just come out of the holes you’ve drilled so some plastic taped around the area will stop any mess. Holes 100mm apart will be easy to fill and you won’t notice them. 

[Nickfromwales]

The more holes you drill, and allow the product to expand out of, the better the fill. Also there will then be little or no pressure applied to the P board. 

Deffo to the wetting. 

[Ferdinand]

Are you better with one of the cans rather than a gun for this, as they come with a flexible drinking straw that can be bent further into the hole more easily?

 

Is that any advantage in these circs? Or can a flexible nozzle for a gun be manufactured / repurposed?

[Stones]

Appreciate the input chaps, very much confirmed my thinking.

 

@Ferdinand, having looked at a few guns, many come with additional nozzles of this type so my thought was to go with that, best of both worlds, better gun control but extended length and flexibility of additional nozzle.