Advice on roof pitch and tiles

[garymcl]

SORRY GUYS - I should have changed my title to Advice on wall plate height!

Hi Guys, first timer here so go easy on me!!

Doing a 40m2 single storey extension to my property, cast the slab saturday, brickies started today. Going well...so far.

Got a pretty poor Structural Engineer, can never get hold of him, and his detailing is really bad. Poor decision given he's done my plans and detailing (albeit all very basic)

The brickies are asking for the height of the extension, my engineer put no dims on his dwgs (and yet they were approved by the planners?)

Anyway, to get the height of the wall plate, would I be right in saying the TOP of wall plate should be set level with the TOP of my plaster board ceiling for my new extension?

And to ensure this ties/flows in with the existing house ceiling, all I need to do is transfer the existing ceiling level outside and then add on the thickness of plaster board? Once that level has been established, simply take off the depth of the wall plate (using a 100 x 50mm wall plate), so 50mm off my level then bob's your uncle?? Or is it not that simple??

Got loads more questions if you want to hear them ha ha ha?

Cheers

 

[noseall]

Yes, you basically have the gist of it, in that the top of the wall plate determines the ceiling height and if you want both existing and proposed to line up, then this is where your wall plate finish should be.

Top of widows and doors, i.e. ground floor lintel height setting is usually at 2100mm and ceilings are typically at 2400mm (all measured from internal finished floor or dpc) or often slightly greater for ground floor.

Certain things can influence the wall plate height setting when merging into an existing building particularly when cavity thicknesses differ. A wider cavity for example can mean that a wall plate sits higher than existing, but this is only relevant at second floor detail and where a traditional roof is being built on an elevation where the roof ranges through.

I would imagine that, on a ground floor single story extension, you will have the freedom of positioning the wall plate so that ceilings will line through.

However, if there is a natural break between rooms then lining the ceilings up exactly is not always an issue. What can be more of a issue is making sure that the soffit and fascia detail are positioned in such a way that the soffit terminates at the door/window heads or higher.

 

[freddiemercurystwin]

Aye to add to noitall's post some heights on a drawing can be difficult to predict with any accuracy, it is normally down to the site workers to adjust heights to suit the existing construction: window heights, ceilings, existing eaves etc etc and any good builder will have no trouble in getting the heights to line through without some numbers on a drawing.

 

[^woody^]

Wall thickness can influence the plate height, but also, if you are matching up roofs, then you need to check that the new rafters are the same depth as the existing ones

Normally, the plate height will be about 300mm above the lintels

 

[garymcl]

Many thanks guys, really appreciate it. Extension well under way. Not without problems that's for sure! Cheers