Mounting on top of insulation

[babba]

I was going to say superglue or runaway, never seen it myself but some good replys on here..

 

[hermetic]

I have seen it done like this on several jobs (insulation on top of rafters), mainly barn conversions and the like. It isn' a particularly good idea IMHO but thats by the by, we used to drill a 20mm hole through the insulation to the rafter, and drop in a peice of 20mm conduit cut to the thickness of the insulation, then screw the brackets through the conduit and into the joists with sheradised screws.

 

[moggy1968]

sounds like a complete pain!! how do you accurately locate the joists?

 

[yellowvanman]

I have seen it done like this on several jobs (insulation on top of rafters), mainly barn conversions and the like. It isn' a particularly good idea IMHO but thats by the by, we used to drill a 20mm hole through the insulation to the rafter, and drop in a peice of 20mm conduit cut to the thickness of the insulation, then screw the brackets through the conduit and into the joists with sheradised screws.

Need to ensure you've got square cuts on the conduit! I guess need at least 150mm long screws, longer if insulation greater than 75mm!

Isn't the conduit is also being stressed by the bracket being clamped directly on top of it!

 

[screwdriver]

we had got some stainless tube cut to length by local firm. very cheap. gives the bracket something to tighten to when the insulation is poorly installed or too compressible.

 

[moggy1968]

I think thats one I wouldn't even quote on!! too much hassle!

 

[hermetic]

Sorry yellowvanman, should have said metal conduit, but screwdrivrs SS would be even better, conduit is in compression, so not a problem.

 

[jerriais]

This sounds like a SIPS construction (Structural Insulated Panel System). As you can see from the name the panel not only provides insulation but also has enough strength to form part of the structure. Very difficult to install on but if you can find the rafters with an accurate stud finder tool (we use on from Hilti) then you can use specialist screws from Ejot or similar to go through the SIPS panel and into the rafter.

 

[pembrokeshire]

6 Inch Nails !!!
Usually there is 3/4 osb on top then cross battens, so plenty of grip if you predrill your fastenings. Something we will see more of I expect
Mark