Adding insulation under a tile roof?

Sp, you wont need to lift your tiles to install the sisalation, if your trusses are 700mm apart buy the 1500mm wide sarking(proper name) cut it in half accurately and run it long ways between the trusses.
You should have 25mm overlap on each side too staple it in place with. Work along the trusses putting in just enough staples to hold it inplace then come back over it with staples every 10-20mm to tighten it up and seal it against the trusses.
To hold the bats inplace until its covered use cheap fishing line just string it accross the trusses and staple it in place on the lower face(the staple height of less than 1mm wont affect the ceiling you put up...)

Hints, dont unroll the sarking to cut it in half... cut the whole roll in half, last time I used it we cut it with a sharp bow saw!
electric or air driven staplers will help save your sanity, if not dont try and do it in one day... your shoulders will kill you unless your used to working in overhead situations!

an electric kitchen knife is great for cutting rockwool or f/g insulation

Charles, I have used concentina foil batts to do exactly the job you want. Easy to put up-just staple them to the rafters up to 50mm away from the tiles. They insulate brillliantly and stop moisture at the same time. Cost effective as well.
Look at www.concertinafoilbatts.com - tim renouf is the guy I dealt with- couldnt be nicer.
regards rosethorn

So this thread can make the uBueat best-of, my summary now is:

Otions for insulating a tiled workshop cathedral roof (new term I just learnt from references in this topic) are:

• Use sarking (nother new term) and standard insulation batts, and finish with gyprock and paint. See Harry72's post above for details
• Use rigid blue foam horizontally and finish with acrilic paints directly on the insulation. See Wildman's post for details.
• Use foil-backed-batts,tape joints with duct tape, finish with gyprock. See micko's post above.
• and Rosethorn suggested concentina foil batts, stapled to the trusses, which in a workshop could be left unfinished, see her post for details.

So many good suggestions, thanks guys my life just got harder ;).

On a slightly serious note, once again I have seen the power of this board and its members. I now have several interesting new options to follow up and a exceptionally good answer to my orginal question.

Thanks to all that responded, your answers and willingness to give are what makes this board be what it is.

Charles

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Originally Posted by spbookie

After a bit of research it seems I may have to provide a waterproof membrane between the tiles and the insulation. Can anyone please tell me if this is true? And if so what should I use as the membrane?

Are there better ways to directly insulate an existing tile roof?

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I don't know if that is true or not. My guess is it's dependant on the local council building regulations.

When I built my second storey addtion (25 years ago) I used sisalation as insulation, as I had a solid Jarrah timber (cathedral) ceiling with exposed (dressed) rafters and laminated Jarrah beams. (Loved that ceiling).

After installing the timber ceiling I then installed 25mm battens on to which the sisalation was attached (reflecting side UP) then the tile battens were placed over these battens and sisalation, then the tiles were placed on the tile battens.

This method provided a 25mm air gap between the tiles and the sisalation and a 25mm gap between the sisalation and the (inside) timber ceiling. This proved to be quite effective in keeping the upper storey cooler.

I know that the supposedly proper way of installing sisalation is blue side up but I could not see the benefit of having the reflective side down??? Besides, the builders of my (then) home did it with the reflective side up. To me that is more logical :D

A combination of sisalation and f/g batts anfd then a 10mm thick mdf liner should keep the workshop nice and cool. It could be a good idea to seal (oil based) the tile side of the mdf.

Hi

Quote:

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Originally Posted by Harry72

Sp, you wont need to lift your tiles to install the sisalation, if your trusses are 700mm apart buy the 1500mm wide sarking(proper name) cut it in half accurately and run it long ways between the trusses.

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DON'T do this if you have to have a moisture barrier!

Sisalation is supposed to overlap HORIZINTALLY (IIRC at least 200mm) so that ANY moisture runs off. If you lay the sisalation VERTICALLY you effectively destroy the moisture barrier properties! It can leak out of the "sides".

Hi

Quote:

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Originally Posted by Harry72

Sp, you wont need to lift your tiles to install the sisalation, if your trusses are 700mm apart buy the 1500mm wide sarking(proper name) cut it in half accurately and run it long ways between the trusses.

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DON'T do this if you have to have a moisture barrier!

Sisalation is supposed to overlap HORIZINTALLY (IIRC at least 200mm) so that ANY moisture runs off. If you lay the sisalation VERTICALLY you effectively destroy the moisture barrier properties! It can leak out of the "sides".

Sisalation is *really* supposed to be installed under the roofing material NOT UNDER THE RAFTERS!

How can you install it directly under the roofing material if it needs a gap of 20mm and dont want to remove every tile and the batton the whole roof structure!
Laying it verticaly does not destroy its moisture barrier effectivness at all.
If you read what I've written its installed 20mm from the roofing material... just like the manufacturer advises too do, not cover the rafters/trusses they are still exposed!