Installation of top-hung bi-fold doors - structural advice

[danieljamesscott]

Hi,

We have a single storey timber-framed extension with french double doors. The roof above the double doors is double glazed.

We would like to extend the door opening by 1/3rd, and install top-hung bi-fold doors. The door company mentioned that the top hung doors would add around 30kg per door so I'm looking for structural advice.

1. What options are available for structural timber, and is there a 'standard' for a single storey beam which would be suitable to hang bi-fold doors?
2. What sort of expert should I have round to take a look. Do I need an architect/structural engineer? Or would a builder be able to work out if the existing construction is suitable?
3. I know this is difficult to answer, but the extension was built around 1980 - is it likely that the standards of the time would mean that the existing construction would be OK?
4. Assuming that the existing construction would need to be reinforced, could someone give a rough estimate of cost/the work that would be required?

Thanks,

Dan Scott

 

[freddiemercurystwin]

I would look for a good architectural technician to oversee the design, produce some existing pans/sections etc and then he can liaise with an SE to see if its plausible and ultimately produce a set of drawings for a good builder top work from. Asking a builder to handle it all is likely to end in tears.

But why not just use a floor supported Bi-fold instead?

 

[danieljamesscott]

Hi,

Thanks for the reply. I guess I was sort of just hoping that I could get someone round to check it out, and they would tell me that it's all OK.... . I didn't realise that 'replacing' the doors would involve so much work. Although we are enlarging the doorway, there is already a fixed glass panel in the space we're expanding into, so the walls won't need to be removed.

We got several quotes for the doors, and we picked this company for a variety of reasons... I guess I don't want to go through all that again...

Thanks,

Dan

 

[freddiemercurystwin]

So you've chosen a top hung door company and you'll stick with that despite the fact that it could easily be more problematic, difficult and expensive to achieve?

 

[danieljamesscott]

Not necessarily... what if I can quickly and easily get someone round who tells me that everything is OK and I can just have the doors installed as is?

That was the whole point of my question.... to find out more about the whole process. I'm no expert and so I'm trying to find out more. Why would it be more problematic, difficult and expensive if I find out that the existing structure is perfectly fine as it is?

Also, the quotes that I have for the top hung doors are cheaper than the bottom hung ones, so I'd factor that cost into the decision.

Thanks,

Dan

 

[danieljamesscott]

Just had a quote of £400 from a structural engineer....

Anyone have any advice on this? What sort of support should there be above a 2m opening in a single storey, with a shallow pitch roof above?

 

[catlad]

The chances of your extension being built with the correct lintel for a set of top hung bi-fold doors are slim I would say.

 

[danieljamesscott]

I've done some more investigation.

Bottom rolling bi-fold doors are looking about £1200 more than top hung (And there are far fewer choices available). I've also taken a look at the supporting beam and it looks like it's 100x100mm structural timber beam.

I know this is a grey area, but can anyone give any advice about what sort of structural support should be in place for a 2100mm opening in a single storey wall, with pitched (lean-to), double glazed roof above.

Thanks,

Dan