Converting bungalow loft - floor joist arrangement and roof support structure

[Richycsurfer]

Hi everyone,

I'm looking to install new ceiling (first floor) joists to my bungalow to be up to to the job to have a room in the loft to give us some more space. In the future we will be looking to add dormers and create a few bedrooms however funds don't currently allow. I've looked at span tables and i'm comfortable with what joists i need, my only concern is installing them while keeping a support network in the roof. The house is around 7.4m x 7.4m and has interlocking concrete tiles.

The current setup is a purlin into each end of the house with a similarly installed timber at ceiling level with support 'props' (x3) off it upto the purlin. (shown in the first pic)

The ceiling joists are nailed into the bottom of the timber (presumably to assist with ceiling sag?). The ceiling joists tie the rafters together in 2 lengths to a middle supporting wall where they are nailed together. The ceilings have sagged so they don't appear to be in much, if any, tension. (simple drawing image 4)

There are also 3x ties higher up 3 of the rafters creating A frames, these have bowed and a plainly not in tension. Can these be removed? (shown with the white arrow in image 3, visible in all 3 pictures.

To install taller floor joists I would need to be rid of the purlin support timber, or massively notch its underside for each new taller floor joist to sit in reducing its strength.

1) Could I safely remove this support timber, install my new floor joists and add some purlin support off a few of these (would 3x suffice again)? Would i need to prop the purlin before removing the support timber?

2) Could another option be to add another purlin next to the other? Doubling up would presumably keep the same strength assuming the new purlin was as large timber as the removed support timber. This may give the option for most space up there once boarded out.

3) Do i need to tie the rafters together above head height level to replace the 3x timbers creating A frames? How many would be recommended?

Any help would be great!

A few pics showing the current roof...

current ceiling joists...

 

[Leofric]

Conversion of loft space to habitable rooms - could this be a case for having it properly designed with a Full Plans Submission for building regulations approval and structural calculations by a structural engineer ; or maybe bring a builder in and let them do it under a building notice and make it up as they go along .

 

[^woody^]

You're guessing at a Heath Robinson sort of frankenloft.

None of your ideas will work. It needs to be designed properly.

 

[Leofric]

It needs to be designed properly.

Exactly. So what do you think Richysurfer , dare I suggest getting somebody to prepare drawings for a building regulations application.