Pick my wall height to tie in with existing flashing

[milese]

Hi,

I'm adding making my conservatory more permanent with addition of extra brickwork and a slate room. Keeping structure same size and shape as conservatory and utilising existing flashing that has been cut into the house.

I've attached two pictures where my finger shows wall height and the top of the ruler shows where the top of the tile will be (where 10mm mortar join + 70 wall plate + 110mm rafter + 25mm batten +5mm tile less 30mm bird mouth = 7.5")

So I can build wall height to give a tile height that is either slightly above or below the bottom of the flashing. I think I'll be best going high and folding the flashing over the edge of the tile, but think I could make it work either way with soakers from 150mm lead?

A slightly higher wall gives me slightly bigger windows which must be a bonus.

Permitted development with no plans.

But I'm bad at decisions so would appreciate any advice please?

Bricky starts Saturday.

Thanks

 

[^woody^]

Measure your total roof thickness perpendicular to the slope line (top of tile to underside of rafter) not vertically like you are doing, then mark that line and extend it to where it meets the line of the internal wall face. Top of tile will be about where the bottom of the lead is.

Then you need to allow for the wall plate height, which is determined by your eaves overhang and soffit height.
Basically the top of the wall plate many be where the underside of the rafter meets the internal wall face, but that will give a big notch, so typically the plate may be lower so that the rafter meets the top of the plate say in the centre, so a smaller notch.

Don't forget lintel depths, or timber depths if no lintels, so that whatever you are using can actually fit in below the rafters.

But TBH, you should not let that existing lead determine your ceiling or roof height if it compromises the internal height. If need be set the frame head heights to match the existing and then se the roof out according to that.

 

[noseall]

utilising existing flashing that has been cut into the house.

Seems like a convoluted way of saving a wee bit of flashing to me. As Woody said, there are many things to consider, not least of all finished height, which will likely be taller than previous. Also pitch may be sightly different, i.e. it may be below the flashing at the top but above at eaves etc.