Replacement roof

[Lindricklad]

The roof on my bungalow has certainly seen better days and I plan to have it retiled. [Note:- I have already created good access to the loft]
It's shape is basically a pyramid with a rear extension in one corner (this area will become a utility room and toilet).
The wooden structure itself is still in very good repair, comprising 4" x 2" rafters with 1.5 " x 0.75" battens.
It has been suggested that I should have all the tiles and battens removed and then felt applied before rebattening and using lighter tiles. [The current tiles are approx. 6" x 4" in size]
However I am rather keen to retain the battens in place and achieve some other form of insulation for the roof, and possibly use similar tiles again. Additionally I will revamp the current loft insulation above the ceiling.
I understand that spray foam is a possibility (to create a 'warm' loft) but I have also read that this is not always recommended. [This would also be difficult to achieve within the rear extension because access is very limited - although I could possibly deal with this in a different way]
Any comments about possible solutions would be much appreciated. Cost comparisons would be useful !

 

[noseall]

I'm not sure what you are asking?

So far you have dictated to us that you are not gonna lose the laths and that you are going to deal with the ceiling insulation and that you will deal with the extension insulation "in a different way" and that you have been correctly told that spray foam is crap.

I can't for the life of me understand why you would not go the extra mile and have the battens removed and have breathable membrane fitted but that's up to you.

So, what IS your question?