Wide(r) sliding doors for the rear wall - what are the implications

[oldkettle]

While preparing to apply for NMA I showed the updated plans to local estate agents. They mentioned that people might want an opening into the garden to be larger than our proposed 3m slider. They mentioned bi-folds  but that's not the point. I am not quite sold on the idea (there is also a window in the kitchen), but the garden is indeed one of the main attractions and I want to understand whether it is technically possible and financially viable.

 

Here is the plan. In the old version I expected the supporting steel to continue the line of the structural wall (the door would have to be moved a bit to the left for this to work). But If we want to widen it to say 5m, I don't know how to support the upstairs. All other internal walls shown apart from the marked one are "new" and were not planned as load-bearing (that's a stage before BC plans).

 

Thanks in advance for any help!

 

[Russell griffiths]

Are you talking about the end with the double doors???

if so it would probably have a steel goal post setup, so two posts either side of the double doors with a steel across, then the long steel bolts either on top if you want it hidden in the ceiling or the side if you want it visible. 

 

Make sense. .??  

[oldkettle]

12 minutes ago, Russell griffiths said:

Are you talking about the end with the double doors???

if so it would probably have a steel goal post setup, so two posts either side of the double doors with a steel across, then the long steel bolts either on top if you want it hidden in the ceiling or the side if you want it visible. 

 

Make sense. .??  

 

Thank you, Russell. I think to make it 5m we'd have to move the steel even further to the right, likely, in line with the other wall, but the principle is probably the same. Do these steel posts need to rest on a separate foundation or can they be set on a slab (this will not be a raft foundation)? 

[PeterW]

2 hours ago, oldkettle said:

 

Thank you, Russell. I think to make it 5m we'd have to move the steel even further to the right, likely, in line with the other wall, but the principle is probably the same. Do these steel posts need to rest on a separate foundation or can they be set on a slab (this will not be a raft foundation)? 

 

Depending on what’s above, you’re getting into the realms of very big steels - 254 or 305mm depth is not unusual and even more than that, the UC columns will become 205 or larger. These require a designed foundation pad and can be up to 600mm square and 900mm deep depending on ground conditions. Not cheap, and very heavy to deal with - upward of 45kg per  metre and you potentially need two side by side for a cavity wall. If it’s taking the floor joists or a perpendicular load then it could be even bigger. 

 

If you've asked an estate agent, it means you’re doing this to sell..?? If so, ignore what they say and put in a set of cheap 3m bi-folds, spend the extra on a bling kitchen and walk away with £20k in your pocket.

 

Asking an estate agent about whether you should open up the back of the house is like asking a Labrador to tell you the football scores ... 

[oldkettle]

7 hours ago, PeterW said:

 

Depending on what’s above, you’re getting into the realms of very big steels - 254 or 305mm depth is not unusual and even more than that, the UC columns will become 205 or larger. These require a designed foundation pad and can be up to 600mm square and 900mm deep depending on ground conditions. Not cheap, and very heavy to deal with - upward of 45kg per  metre and you potentially need two side by side for a cavity wall. If it’s taking the floor joists or a perpendicular load then it could be even bigger. 

 

Thank you, Peter, this is a very clear picture.

Can't say I am too worried about having to dig for the columns as the one inside the house will be where we are digging for the slab anyway, and the foundation will be new so at least 1m deep anyway. 

 

 

7 hours ago, PeterW said:

If you've asked an estate agent, it means you’re doing this to sell..?? If so, ignore what they say and put in a set of cheap 3m bi-folds, spend the extra on a bling kitchen and walk away with £20k in your pocket.

 

Not planning to sell at all. I asked for two reasons. First, they are good agents and handle probably half of the properties on our local market, so know what people ask about in case we like it as well (but missed). Second, I am somewhat concerned about Brexit and want to know we have a way out if the worst comes to worst. 

 

Do you reckon the extra cost of those can be £20K? I checked the steel prices and it seems not too bad, about £300 per column with a comparable price for a beam. The thing is we are going to have to support the first floor and the attic above this open space anyway. 

[PeterW]

I reckon your steel cost will be £12-1500 when done as it will need fully bolting on site. Engineer will add another £3-400 depending on location. 

 

You'll also need to do either an NMA or a new planning application.  

[oldkettle]

Yep, I am preparing an NMA. £2K sounds OK. 

 

Thank you!