rafter insulation - essential?

[redwin11]

Hi everyone.

my attic space is currently a bit of a mess and i want to smarten it up.

At the moment, half of the floor is boarded up (i think larger joists have been used for this section, but i will pull a board up and confirm it) and the roof tiles are exposed, letting in a lot of dirt.

My initial idea was to insulate between the rafters and plasterboard it up, however, the rafters are only 65mm deep, which means there wouldn't be any allowance for the 50mm airflow.

As the attic floor is insulated, and I am going to have flooring put down right across it, do i need to insulate the roof?

I don't want to lose headpsace by increasing the rafter depth, so could i just plasterboard the roof? If so, would i need to put some sort of covering over the inside of the tiles?

Thanks in advance.

 

[noseall]

if my roof lacked a membrane i.e. sarking felt, breathable membrane etc, then i would not attempt any of the above.

 

[redwin11]

if my roof lacked a membrane i.e. sarking felt, breathable membrane etc, then i would not attempt any of the above.

Why not, and what would you suggest?

 

[Sledge]

Problems you might face w/o sarking felt:

- water ingress via cracked tiles, or just by blow through / capiliary action during rain. What little of this which might currently be occuring is being evaporated by airflow through the loft. Sealing the rafter space will prevent this drying and rot your rafters and your rafter boarding;

- condensation on the inside of the plasterboard will occur when the warm moist air below hits the shockingly cold plasterboard, which isn't shielded from the outside temperature either by sarking felt or insulation.

It also sounds like you are attempting to make a habitable sapce above a ceiling. Ceiling joist are meant to close couple the rafters to prevent lateral thrus on the supporting walls / wallplate and hold up a light ceiling (<0.25kN/m^2). They are not meant to bear lerger static loads or indeed imposed loads. Ceiling joists should at most be used for a little light storage.

If you wish to live in your loft, you need a separate floor, supported indpendently from your ceiling, and you need to put all of this before building control, unless you fancy them demanding you rip it all out.

 

[mointainwalker]

He's not listening, it was 4 1/2 years ago !! Why sudden interest ?