Insulated most of ground floor, how to do awkward bits?

[nishnish]

Hi,
Insulated under ground floor in 1890 house, from crawl space, by putting space blanket between all joists.
Now the awkward bits; the small gaps between wall and joist (4-6cm) and also the joist structure around fireplace.
I saw a suggestion here to fill the gap between wall and joist with expanding foam. However, expanding foam doesn't work very well when being sprayed upwards, as the can can't be held upright.
Had a go today. Got very little foam out of the can. A lot of it fell out onto ground.
Any ideas how to fill the space from underneath?
Thanks.

 

[DAZB]

You could either cut and friction fit Kingspan or Celotex boards or even cram plenty of rockwool into the gap. A small strip of timber every so often screwed to the underside of the joist will help prevent it ever falling out.

 

[nishnish]

Thanks for the reply.
I did contemplate that, but thought it sounded so much better to fill those irregular gaps with foam. Until I tried it
I suppose a foam gun would have the same problem, due to the can being upside down, on the top of the gun?
I need a flexible ~1m nozzle to allow the can to be upside down and the nozzle end to still reach the floorboards.
Will rockwool be ok against the external walls? Won't it wick moisture from the no-DPC fabric?
Thanks.

 

[DAZB]

Rockwool will have no problem with being in contact with the walls as long as the walls are not, or do not, get wet.

 

[nishnish]

They get damp not wet.
Is that ok? Or were you referring to any moisture?
There's no DPC and there is a concrete patio outside (27in below ground floor level inside) where water pools against the wall; which needs a sledgehammer taking to it (the patio). Another job

 

[seasickstevie]

How about nailing a strip of plasterboard or hardboard or anything similar to the bottom of the joist, crossing the gap and touching the wall. Dill holes just big enough for the nozzle every so often. Then fill the gap with foam.
After it's set, you can hack away the plasterboard/hardboard to avoid it wicking.