DIY full height/width dormer conversion -need advice please!

[Rubyblueshoes]

I've just bought a 3 bedroom mid terraced house in South East London and really want to put in a rear facing dormer (full height and width). The quotes we've received have been about 30k upward and we only have 20k to do the entire house. My father is an experienced builder and he was involved in the building of three other dormers in the past at various stages of the process. He also buys and does up properties in France and has worked on roofs a lot over the years.
He is willing to build the dormer so the cost will be entirely materials and his supporting labourers as he will project manage.
My questions are as follows:
1) is there anywhere I could see/get a rough illustration or plan for a similar project just for comparative purposes?
2) as I understand it, the rear wall has to sit 20cms from the supporting back wall. However I've seen other dormers that seem to sit ON the wall. Am I wrong or what are the rules with this? Additionally is there a minimum distance from the apex that the flat roof has to start from?
3) though my father has a lot of experience, he hasn't kept up with the newer trends in terms of insulation. He thinks that a simple layer of Kingspan between the joists, then plasterboard should be enough for the roof insulation however other forums suggest otherwise. My father's other suggestion is using Triso but it seems to have very mixed reviews. What insulation would you suggest?

 

[freddiemercurystwin]

For what you can do without having to apply for planing permission see here: http://www.planningportal.gov.uk/permission/commonprojects/loftconversion/

This is a useful guide clarifying the aforementioned: http://www.planningportal.gov.uk/uploads/100806_PDforhouseholders_TechnicalGuidance.pdf

You will very likely need a structural engineer to do the structure. Even though money is tight if you are no up to speed with the Building Regs you could do worse than to employ a technician to do some Regs drawings.

Phoning Kingspan or Celotex will determine the exact insulation required or Celotex have a natty U Value checker online if you search their website.

Triso has mixed views as for many years it was not accepted by some Building Control's there is speculation that their method of testing is insufficient, it is expensive and you need an air gap each side of it so the thickness saved is not as attractive as first it seems!

The following details are a typical dormer, insulation thickness will be incorrect because requirements have changed (increased) since these details were produced.

Untitled

• freddiemercurystwin
• 14 Apr 2010
• 12

Untitled

• freddiemercurystwin
• 25 Apr 2010
• 24

Untitled

• freddiemercurystwin
• 8 Jun 2010
• 20

Untitled

• freddiemercurystwin
• 22 Nov 2010
• 4

 

[stuartturbo]

Just in the progress off sorting mine. A 2 bedroom Victorian terrace 3rd room upstairs is the bathroom
Mine is all timber construction so no steel work i used a structural engineer in Rochester whom has a list that brakes everything down to pass Building regs and a draftsman sorted out regs and a drawing ( this is not that detailed)
Mine is a terrace also and full width full height and my dormer come straight off the wall.
Kingspan and one layer of there plaster board is enough to meet current standards I seem to recall 25mm insulation and the board