Out of my depth - Air Tightness and Insulation....

[Mulberry View]

Just now, Russell griffiths said:

What I’m not seeing in your drawing @Mulberry View is how the standing seam is fixed down. 
every time I’ve seen it it’s fitted with a clip or bracket screwed down to the wooden substrate. 
 

your drawing to me looks like you have the kingspan insulation and then a separation membrane then the zinc. 
 

how’s this zink fixed down. 

 

@Russell griffiths I completely agree. Another of the mysterious unknowns that was apparently 'out of scope' for a £20k Architectural design package.

 

I have good Zinc guy lined up. It's early days yet, but he's also a self-builder and has offered me lots of help with the details, so I'm going to sound him out on it as a first port-of-call.

 

So many woolly details though, people have paid a quarter of what we did for their design and came out clearer than we are. If I had the headspace for it, I would like to employ someone to inspect our plans and critique the details to form the basis of a case against the Architect, but also as a way to know what needs sorting out.

[Russell griffiths]

I would take your zinc guy out to lunch with all your roof details and pay him for 2 hours of his time. 
 

As far as I’m aware your zink will sit on a continuous membrane that covers a sheet of ply. 
your insulation sits on the tops of the rafters. 
does the insulation require a sheet of ply /osb to stop it crushing onto the rafters ?????
 

the drawing the architect has done is a similar spec to a rubber membrane type roof where the rubber is adhered to the insulation, the insulation normally has a fleece face and the membrane is glued to this. 
 

there is nothing in that drawing to show a zinc fixing. 
 

I would also talk to the zinc supplier and get a fix down drawing. 
 

have you fitted the roof joists yet ?

[Mulberry View]

1 minute ago, Russell griffiths said:

I would take your zinc guy out to lunch with all your roof details and pay him for 2 hours of his time. 
 

As far as I’m aware your zink will sit on a continuous membrane that covers a sheet of ply. 
your insulation sits on the tops of the rafters. 
does the insulation require a sheet of ply /osb to stop it crushing onto the rafters ?????
 

the drawing the architect has done is a similar spec to a rubber membrane type roof where the rubber is adhered to the insulation, the insulation normally has a fleece face and the membrane is glued to this. 
 

there is nothing in that drawing to show a zinc fixing. 
 

I would also talk to the zinc supplier and get a fix down drawing. 
 

have you fitted the roof joists yet ?

 

As I said, the Zinc guy has offered to help me with detail drawings. In all honesty, he is awaiting our decision on colour, one we should have made weeks ago. If he's as good as he sounds, I think he'll be a goldmine of info once I get to that point. I haven't furthered to detail conversations with him yet, I will do that soon as we need to bump the date with him once more.

 

The roof joists are not fitted yet, why do you ask?

[Russell griffiths]

I’m curious about this fix down detail 

so I did a google search 

it looks like a standard detail what you have there, look on VM zinc. 
so I’m presuming there’s a clever fixing that goes through the insulation into the plywood underneath. 
 

if this is the case I think everything is ok, I’m only familiar with a system that fits to a solid substrate. 
so it’s better I don’t continue second guessing your buildup, without the full knowledge of what system your using. 
look on the manufacturer website I think you are ok.  
 

 

[Russell griffiths]

Had another look while having lunch 

@Mulberry View

i have seen your set up before but had forgotten, getting bloody old I’m afraid. 
the zink fixes down with a clip, this clip has a raw plug looking thing that punches through the insulation, it is hollow like a drinking straw but with a washer at the bottom, once you have pushed it through the insulation you drop a screw down the straw, it hits the washer at the bottom and you screw it into the plywood. 
 

so I defo think your drawing is fine. 
the only thing stopping you adding more insulation would be if the manufacturers make this clip/ straw thing in different lengths, or do you add a longer screw. 
 

a question for the roof manufacturer. 
 

all looks good to me know. 
 

just got to get a continuous vcl from the walls to the one on the roof. 

[Mulberry View]

1 minute ago, Russell griffiths said:

Had another look while having lunch 

@Mulberry View

i have seen your set up before but had forgotten, getting bloody old I’m afraid. 
the zink fixes down with a clip, this clip has a raw plug looking thing that punches through the insulation, it is hollow like a drinking straw but with a washer at the bottom, once you have pushed it through the insulation you drop a screw down the straw, it hits the washer at the bottom and you screw it into the plywood. 
 

so I defo think your drawing is fine. 
the only thing stopping you adding more insulation would be if the manufacturers make this clip/ straw thing in different lengths, or do you add a longer screw. 
 

a question for the roof manufacturer. 
 

all looks good to me know. 
 

just got to get a continuous vcl from the walls to the one on the roof. 

 

OK, fair enough, but these fixings will penetrate the vapour barrier, will they not? Is this an issue?