Mono-pitch using deep joists, how to detail fascia?

[r896neo]

I am helping a friend planning a barn conversion. It is 1850s and has solid stone walls with brick quions, the walls are approx 450mm thick. Its a long thin rectangle 6m by approx 25m

It has a Mono-pitch about 20 deg and as the span is about 6m and as it will be self built I had thought JJI type joists will work well requiring no purlin and being easy to install.

The joists for that span will be about 300mm deep but this is going to leave a very deep fascia which on a traditional stone building will look awful.

Ideally to retain the traditional look there would be a flush eave with no fascia but im not sure how to detail this given the solid stone walls and the deep joists?

Initially i had thought of building a soldier course of reclaimed brick on the exterior, which would look ok and fit with the quoins, and then leaving the wall plate low on the inside but concerned about damp proofing it.

Anyone any experience of this type of detail or any ideas? I know very little about roofing other than the obvious so apologies if this is rudimentary.

Thanks

 

[chappers]

sounds perfectly feasible, just wrap the joist ends in DPC if you're concerned

 

[noseall]

A 6m mono pitch.

Are you confusing joists with rafters here? Has the roof been designed and will it be built with a joist/rafter arrangement as opposed to just vaulted? Is there any steel involved?

My guess is that the rafters can be designed so that they stop short of the outer skin allowing you to say build up a corbeled masonry eaves detail?

Either that or extend a smaller section rafter down from and connected to the main rafter ends and build up the masonry to suit - if a conventional timber eaves detail is required?

 

[freddiemercurystwin]

H'mn, a barn conversion on a Notice, what could possibly go wrong.

 

[r896neo]

It will be a full plans submission so you can calm down Freddy.

Its easier to decide how to do something well in advance on paper and then you can rub it out and try again hence trying to get some ideas now.

I only use the term joist because of the plan to use JJI engineered type. They are of course rafters but because of the make up of the joists cutting a normal eaves arrangement isn't easy plus the desire for a flush eaves.

If the brickwork was corbelled out would the roof sheet or tile edge normally be bedded on mortar? How are the rafter feet detailed?

The plan for simplicity was to use the jji's and have a vaulted ceiling. There is most likely going to be a reinforced ring beam on the wall tops.

An engineer will be designing the roof, we're just thinking through the process for the cosmetic details

 

[freddiemercurystwin]

Let the designer handle it then, if he's good and his brief is good.

 

[r896neo]

Yes i suppose so but how often have you seen a design which is either the easiest way out (Normal overhanging fascia and soffit) or over engineered and over expensive just for arse covering. If i can get ideas for different possible ways to detail it which are easier to work with then at least its somewhere to start the inevitable conversation.

Cheers

 

[freddiemercurystwin]

if he's good and his brief is good