How do I "Tie" a new roof to stone walls?

[disclosure]

I am re-roofing an old stone barn. The roof and trusses have gone a long time ago! I need to fit new roof trusses which I have drawings for - How do I attach these to the tops of the stone walls - do I need to lay and fix a purling (is that the right word - a thick plank) along the top of the walls - if so how is this fixed into place and are the trusses then just nailed onto the purlin??

Mike

 

[chappers]

The plank at the top of the wall is called a wall plate and is usually (100x50mm ) use right angled galvanised straps to hold it down (ifit doesnt matter if they show or the inner walls are to be plastered)they are a meter long with a shorter section bent over at right angles and should be placed 1m apart along the wall plate screwed down to the timber and fixed with plugs and screws to the wall there is no need to fill all the holes.
If it matters if they show then use chemical fixings drilled down into the masonry.
If you are actually fitting a trussed roof then the trusses should be fixed with truss clips, or if you are fitting a cutt roof then the rafters are just nailed to the wall plate

 

[legs-akimbo]

Many old buildings neccesatate a concrete ring beam as they are to unstable for the traditional wall plate, something you will need to take expert advise first hand on.