Can I Fit Bi-Fold Doors to the Inner Skin of Cavity Wall?

[spamhead]

Hi - looking for some advice please?

I'm having a rear extension built and the intention is to have bi-fold doors at the corner that create an 'open corner', with minimal structure blocking the view (apart from a 100x100mm square section corner post).

The steel frame and corner post have been built, and the corner post has been set to the inner skin of the cavity wall.

The problem I now have is that if I fit the bi-fold doors to the outer skin of the cavity wall, the door handles of the bi-folds will be difficult to access as they'll be behind the corner post.

I've had 3 window companies around and they all seem to want me to build a new block corner on the outer skin, to line up flush with the internal steel post. However this kills the concept of an 'open corner'. I'd just like to check to see what people think my options are?

One solution may be to fit the bi-folds between the corner post and inner skin wall - but will this be possible in terms of weather-proofing the exposed cavity etc?

 

[freddiemercurystwin]

Did you have a set of construction drawings produced showing the relationship of the wall, glazing and column?

 

[spamhead]

Unfortunately not. The architect was vague with that detail, leaving it to the structural engineer to design the steels. And the structural engineer just provided hand-drawn sketches calcs and steel details, with no reference to the glazing.

 

[freddiemercurystwin]

If it had been designed properly it would all work out, lazy arse architect, I would be getting your architect to get involved, I suspect in reality the best you can hope for now is a larger column in the corner clad by the door supplier, a masonry column is just a lazy solution. Are you building this extension yourself or do you have a builder?

 

[spamhead]

If there's no way of fitting the doors to the inner skin then I guess I'll have to build a column on the outer skin for the doors to fix to. If that's the only solution then I don't mind doing this in blockwork, as I'll clad it in timber, or render it.

I'm meant to be project managing the job and bringing in the various trades required, but this mess isn't making me look very good at it!

My wife is going to think I'm proper plonker - she's expecting an amazing open corner, but with a 300x300 column, and the thickness of the internal and external finishes, plus the thickness of the door frames - there'll probably be something like a 400x400 column in the corner.

I'll ring building control and see what that say about fixing door to the internal skin - I think I know the answer, but worth a try.

 

[freddiemercurystwin]

I think this is about the best you could achieve without moving the steel:

Your architect should have done a detail for this corner and ensured that the column was offset, assuming he was responsible for liaising with and checking the engineers drawings and avoided this predictable error.

 

[spamhead]

I spoke to my building control officer earlier today and he advised that he saw no problem in me sitting my doors on the inner skin and fastening directly to the corner post, which would be the best option I currently have for minimising the corner structure. As long as I seal up the exposed and open cavities (by toothing-in return blockwork), which would be now be external, rather than internal to the bi-folds.

This sounded pretty positive, so I then had a chat with my bi-fold supplier to discuss. However, he advised that if I sat the bi-folds on the inner course then I'd have a problem with water drainage, because the door cill wouldn't be long enough to bridge over the cavity and over the outer course.

Next I had a discussion with my joiner who's pretty knowledgable about general building. He advised that I should be able to install a tray-damp beneath the bi-fold doors. i.e. install a 600mm dpc beneath the bi-folds, that then drops down to a lower course of bricks on the outer skin, but still above the main dpc. In theory this sounds like it should work, so I'm looking into this now. (I'm doing a sketch drawing to help explain).

If none of this works, then your drawing is pretty much exactly what I'll have to do. It's not a bad option, but I'll fully exhaust the minimal corner post option first. (cheers for the drawing!). Attached is the detail my architect gave me. It's pretty vague, but you can see it sites the corner post on the inner skin and my structural engineer has blindly followed this - I didn't pick up on it so I didn't stand a chance!

 

[Gazman16]

Large slate cills may be an option

 

[freddiemercurystwin]

How can you tooth up the cavity without avoiding a massive cold bridge?