Flat roof insulation at edges and joining neighbours roof

[dt96]

Hello,

I am about to replace a felt flat roof that covers an old coal shed and outbuilding that is connected to the back wall of my house. My intention is to convert the rooms that currently have no heating to a study and small second bathroom.

As the building is single brick and has a concrete roof I am considering how I can effectively insulate the roof to prevent condensation (as it is currently a problem being a cold room). From the reseach I have done it appears te best way to do this would be to make the ceiling a warm roof which seems relativley straight forward, but I do have a problem.

One side of the Flat roof is shared with the same outbuilding that my neightbour has, with the only feature between the two flat areas being a small ridge under the felt that prevents the water from flowing between the roofs.

If I add insulation of about 100mm to the top of my roof it will raise the height above that of my neighbours roof and I am concerned about the knock on effect of this to the roof next door, therefore I was wondering how I should go about terminating the insulation where the roofs join to keep the water on my side fo the divide; for example should I terminate the insulation early so I can form a channel next to the rige between the two roofs therefore preventing water from flowing on to next door?

I apprecatie any comments about my approach and any advice with this as I cannot find any information online relating to this type of problem?

Thanks for your help in advance.

 

[pinenot]

Add the insulation externally...pinenot

 

[Alastairreid]

I wouldnt stop the insulation short!

Possibly a couple of course of brick built off the slab with a coping stone.
Then you can butt the insulation tight to the wall and weather with a lead apron.
Just an idea as i dont know what it looks like.

 

[Alastairreid]

Add the insulation externally...pinenot

As he said a warm roof i assumed it was externally pinenot.

 

[pinenot]

I meant on top of the felt roof membrane. That way the felt acts as a vapor barrier and there is less internal condensation...pinenot

 

[dt96]

Thanks for the advice.

I am interested in adding the insulation on top of the membrane to use it as a vcl and then adding the insulation on top.

Can anyone point me in the direction of a website that shows how this is done, especially how I finish the edges?

Thank you.

 

[dt96]

alastairreid - my main concern is the side of my roof that is shared with next door. Although there is a ridge where the two flat roofs join it is less than 5cm so how would I deal with the side of the bricks that joins my neighbours felt?

Thanks

 

[Alastairreid]

http://www.the-flat-roof.co.uk/Sect3_5.pdf