mezzanine level - roof/insulation queries

[tiggy748]

we have two small double beds with no real space for storage wardrobes etc, but both rooms have extremely high ceilings and the loft above is another 3m odd in height

I am considering vaulting the ceiling and putting in a mezzanine level in both rooms.

We would need to remove the current ceiling and drop this - I take it the joists that the ceiling plasterboard is attached to are not structural so can be removed?

The roof itself has no ties or struts - just purlins. we have vaulted a ceiling in the past and used kingspan between the rafters, but kept the wood exposed. This time they are are not worth exposing, so aside form the purlins (which id like to keep exposed if poss) i wouldnt mind insulating between the rafters as well as over the top for serious insulation.

I seem to remember also that when we vaulted a ceiling we had to change some of the roof tiles for ventilation - can someone remind me, and tell me what we'd need to do in this case please?

Thanks

 

[catlad]

You could knock your ceilings out and hope for the best!!!
I would advise you to get a structural engineer to design
you planned modifications.

 

[tiggy748]

You could knock your ceilings out and hope for the best!!!
I would advise you to get a structural engineer to design
you planned modifications.

obviously...

 

[vinn]

Ceiling joists are structural - they help prevent roof spread.

 

[JohnD]

and roof spread pushes your walls over so the house falls down.

Which is not desirable.

 

[tiggy748]

Ceiling joists are structural - they help prevent roof spread.

we removed them in the previous vaulted ceiling we did - but the beam configuration was different , so in this case as we would need to remove them, how would we reconfigure the structure to stop roof spread? would BC ask for wall ties ties?

Im just gathering as much inf as possible to decide if its worth getting a builder out to quote

 

[tiggy748]

what about replacing with collar ties? This doesn't seem an extreme or expensive procedure if suitable. And i think we have enough height to install them where diagrams would suggest they normal sit.

 

[vinn]

You need professional opinion(s) on site there are too many variables to advise on this forum.

 

[tiggy748]

and roof spread pushes your walls over so the house falls down.

Which is not desirable.

lol well in this case it might be easier to rebuild from scratch

 

[tiggy748]

You need professional opinion(s) on site there are too many variables to advise on this forum.

ok so moving on from the structural issues - what about the insulation and ventilation options?

 

[noseall]

ok so moving on from the structural issues - what about the insulation and ventilation options?

obviously...

The arrogance of some people, especially those seeking advice.

Unless your roof is covered in a breathable membrane then you will need to introduce bottom to top air-flow to vent the space (25-50mm air gap) that you will have created above the insulation.

 

[datarebal]

you will need to introduce bottom to top air-flow to vent the space (25-50mm air gap) that you will have created above the insulation.

You could do this while its all on the ground!

 

[John D v2.0]

what about replacing with collar ties? This doesn't seem an extreme or expensive procedure if suitable. And i think we have enough height to install them where diagrams would suggest they normal sit.

It's indeed not extreme or expensive, and they would normally sit in the top third of the rafters. They work to prevent the ridge opening up under unbalanced loads eg wind. They wouldn't do anything useful to stop the rafters bending outwards at the bottom, you need to tie the rafter feet together, in the bottom third. Ie ceiling joists.
An SE will be able to design something appropriate possibly with a structural ridge beam to take the weight.
Regarding the insulation it's fine between the rafters, make sure the felt/membrane can still sag between rafters at least 10mm. Also put a vapour barrier on the warm side to stop condensation in the timbers.