block laying Building the external block work before the internal and what insulation to use

[Ttw]

I am in process of doing a garden room that will be built in mind of becoming an annex in years to come. 

 

I'm unable to lay 3 elevations from outside my property and wondering if I can do the external block work first from within the build (off the slab) 

 

I've ordered 50mm Kingspan insulation but because of needing to build this way would I be best swapping for some form of full fill cavity rock wool type insulation (100mm cavity) 

 

Any help would be massively appreciated. How have I never used a forum before.. The info on here is amazing

Edited May 26, 2020 by Ttw
More information

[Declan52]

It's done all the time. Called building overhand. 50mm insulation is a bit light. It's as easy to build either type of insulation in. What are your drawings telling you i.e do you have extra insulation on the inside skin or is the 50mm all you are putting in.

[Russell griffiths]

If you want this to become an annexe in future you would be better off building it to building regs now so you don’t have to rip it to pieces to add insulation when you do convert it. 

[Ttw]

2 hours ago, Declan52 said:

It's done all the time. Called building overhand. 50mm insulation is a bit light. It's as easy to build either type of insulation in. What are your drawings telling you i.e do you have extra insulation on the inside skin or is the 50mm all you are putting in.

Thanks Declan Its just if I was to build the outside skin first then I'd not be able to have the kingspan on the inner skin and doubtful that that's acceptable? What's your opinion on using a good quality rockwool and filling the cavity? Appreciate your input 

Edited May 26, 2020 by Ttw

[Ttw]

1 hour ago, Russell griffiths said:

If you want this to become an annexe in future you would be better off building it to building regs now so you don’t have to rip it to pieces to add insulation when you do convert it. 

Thanks for your input Russell, I'm going to do it to the spec that I had on an extension to my property but not able to build in the same way in terms of access. Definitely agree with getting it right first. What's your opinion on me building the external block work then filling the cavity with rock wool type inso and then building the internal block work up to it? It sounds simple but I've been out the industry for 10 years and don't want to miss any tricks.....my memory is like a sieve 

[ADLIan]

MIs and BBA certificates for PUR cavity insulation show insulation on inner leaf. Mineral wool full fill can be built with either leaf leading. Leading with outer leaf is better practice.

[Ttw]

14 minutes ago, ADLIan said:

MIs and BBA certificates for PUR cavity insulation show insulation on inner leaf. Mineral wool full fill can be built with either leaf leading. Leading with outer leaf is better practice.

That's great news, thanks for confirming it for me. See how my bones hold up to throwing blocks about now. Cheers again mate.