Logical order of play for fitting steels for a flat roof single storey extension

[Ron_H]

Hi all,
as a complete newb to the self build world I'm about to embark on a single storey flat roof extension to open up the ground floor, usual stuff - lots of glass etc.
To get the open plan into the new extension I need 2 RSJs to hold up the 2 skins of the back wall. I want the steel to be recessed into the ceiling to give a continuous ceiling. All the guidance says this is done after the extension is built and weather tight.
What I'm wondering is, how do you build the extension and make it weather tight when the inner end of the joists are to be fixed to a timber filler in the steel and the steel isn't in yet?
I have suggested fitting the external steel first, then building the structure into it then, when done, do the internal steel and knock through.
Am I being an idiot???

 

[Notch7]

I would suggest getting the extension up to concrete oversite then do steels.

The inner steel has to go in from outside.

The order of events is critical, you need the steels down on the ground, acrows and strong boys go in as the brickwork comes out. Strong boys with the handle on top can be a pain, the obes with handle at back are better.

Genie lifts to raise steels. Probably need fork extensions

You dont need to take out all the brickwork below, that can be done after extension up - maybe thats what youve read. Note: the odd brick may have to come out to allow enough reach for forks.

Some builders cut out a channel in the brickwork above the steel and fit a tie rod to stop brickwork cracking. But avoid where the cavity tray will go.

Flush steels are a lot of work.......

This is just an outline so Im not saying its correct, Im sure a pro builder will be along to give better advice.....

 

[^woody^]

Up to slab level, cut the opening, put the beams in but leave the wall up, then build the extension.

 

[garyo]

I have suggested fitting the external steel first, then building the structure into it then, when done, do the internal steel and knock through.

I did exactly that six months ago on my 2-storey job so that I had a working platform to continue the build whilst minimising the chances of divorce. Knock through was then left to the last possible minute. Worked well for me.

 

[garyo]

Flush steels are a lot of work.......

Haha yes.. Had a belly full and still ended up with a little 20mm down stand but it's well worth it.

 

[John D v2.0]

Haha yes.. Had a belly full and still ended up with a little 20mm down stand but it's well worth it.

depending on the situation, if you're redoing the existing room, dropping the existing ceiling 20mm might be an option there.

 

[Benway]

Can be done but as others have said a flush ceiling adds a lot of pain. Our extension was built to roof level then large "slots" made in the house existing wall to insert the steels. See here for the full story.