Using strongboys for opening supporting wall

[parksy]

Hi All

I am removing a supporting wall between the old exterior of the house and the new 'lean-to' extension. Because the 4 metre lintel will be fitted into the ceiling cavity I can't needle it but will be using 4 strongboys on the outside and 3 acros supporting the ceiling on the inside. I will also have a couple of temporary acros to use directly under the wall. The wall is a con block cavity wall.

I have spoken to builders and structural engineers so basically know what I am doing but am taking it slow - for obvious reasons. I am interested in any general advice (apart from 'get a builder in!' ) but have two key questions:

How high above the lintel should I be putting the strongboys be - I have heard 18 inches but can this be more or less?

Can the strongboys be used to support just the outer skin? Because the inner skin is tied to the outer and sits on the joists and the joists are supported on the inside would this be enough or do the strongboys have to go through both skins of the wall?

I have a system in ready to lift the lintel into place but the awkward bit will be getting it between the support piers and the strongboys at the top. Is it ever an option to lift the lintel into place and then build up the support piers and the concrete cap with the lintel already there?

Many thanks for any help and for reading this far!
Chris

 

[splinter]

I know you have said you cannot put needles in, just wondering why you can't put them above the ceiling height and block them of the ceiling with acros under the ceiling ,if you could this would makeit easier as you would have more room to manouvre the lintel into place,with longer needles in place

 

[parksy]

Hi

One of the rooms above is a bathroom and so it would mean a lot of expense taking up floors and removing bath in order to support the needle on the inside.

 

[splinter]

the only other thing i can suggest is to put the lintel in from the inside ,as you should have enough room between the acros on the inside and the wall

 

[parksy]

I can only do that if I wait until the lintel is lifted into position before I build up the support piers, because I would like the lintel to be within the roof cavity rather than sitting below the ceiling. Is there any reason why I can't build the support piers after lifting the lintel into place?
Chris

 

[splinter]

What is going to hold the ceiling up if the lintel is above the ceilng height,I sure I read that you was going to prop the ceiling up on the inside to hold the inner skin of blockwork up

 

[parksy]

Ahhh - I should have made that clear! The ceiling joists will sit on the bottom flange of the 'I' section lintel - or will be attached to a timber that sits on the bottom flange.

Chris

 

[NS215]

yes put the lintel in then prop that then build up the piers and leave for a 4/5 day period before removing all props to allow for curing

 

[parksy]

Thanks both of you for your advice and suggestions. It's been a great help.
Chris