Advice on renewing roof on brick outbuilding

[johnacky]

Hi all just after a little advice. I have a small brick outhouse approx 3 x 3 meters, which has been left to rot for years by the previous occupants. The roof, door, joists, roof boards and window in the outbuilding were totally rotten so I removed them. This left me with brick walls and concrete base. Having ordered all the materials, I decided to use the same layout as the original roof. I battoned the walls, and replaced the joist. I then boarded the roof using 18mm OSB board, and managed to put a layer of Homebase garage roof underlay up, before I called it a day. I nailed the underlay straight onto the new board, and painted bitumen over the joints.
It is my plan to put a layer of felt over the underlay using the bitumen paint. Will this be ok. Since putting the underlay up it has rained for the past two days.
Just wondering how long it will take for the underlay to dry out, and why I can put the felt on the roof and finnish the job. Will the OSB board be ok if it gets damp.
Are there any other considerations I need to take on board, as I am a complete novice when it comes to DIY.
Many thanks

 

[Alastairreid]

hi, 4mm mineral capsheet to complete your roof! either bond it on using cold tar or felt tacks.
remember to form a drip going into your gutter and the edge details are well fixed down.