Insulation advice please

[mark2011]

Hi,
I just thought that I’d ask if anybody had opinions on insulating roof spaces. Weather permitting, next weekend I’m planning on replacing the polycarb roof on our conservatory/lean to with lightweight tiles. The existing structure has timber joists so I’m planning on insulating between them. The joists have 2x3 cross members at the very top which leaves me with approx. 100mm below it. I’ll need to put noggins in (45x70) to screw the plasterboard to and to add rigidity to the joists as they have 900mm centres. That leaves me with 50mm open space and the 45mm deep area in between the noggins. At present I’m planning on putting some 50mm Celotex in the open space but I’m undecided what to do with the area in between the noggins, if anything?
I’d be grateful if anybody had any suggestions what to use, preferably keeping cost in mind?
Possibilities:

• More Celotex? I'm assuming that 50mm won't compact to 45mm so maybe use 25mm thick?
• Insulation wool?
• Leave it?
• Any other recommended products?
• Is Celotex any good in the 1st place?

Any comments would be appreciated.

Thanks

Mark

 

[motorbiking]

TB045 comes in 45mm sizes and is designed for the job you are considering. Cost wise probably going to be cheaper standardasizing on the 45mm board. Even the 25mm board will give noticeably better performance. I assume you have checked that your new roof can be supported by the structure?

 

[mark2011]

Thanks for the reply. Please excuse my ignorance but I've just Googled TB045 and it's showing me digger parts? Is that TB4045 Celotex? I was planning on buying from Wickes but I don't think they stock that size. Can you recommend a supplier please?

I've been told by a local tradesman that I should be fine with the existing structure to support the weight. It has brick outer walls with timber joists. Is there another check that I'd be able to do to make sure? I'm in the early stages and haven't purchased anything yet.

 

[mark2011]

I'm currently looking into getting a structural engineer to have a look at it.

 

[motorbiking]

Lots of suppliers offering TB040 at around £15 a panel. Insulation giant etc.. But local companies would be cheaper due to delivery costs.

After insulating the roof what are you going to cover it with? plasterboard? t&g? this all adds weight.. You might need to think about some additional cross bars.

I assume you have something like this:

You need to check the tiles can cope with the roof angle also. Second the triple poly panels will be attached top middle and bottom, so act as bracing, your tiles wont. Is it absolutely necessary to switch to tiles?

 

[mark2011]

I've attempted to add photos in its current state. The existing roof is awful and needs changing.

I've had an estimate from a structural engineer of £200 to check it out. The local roofer says it will be fine so I'm not sure where to go.

The pitch of the roof is about 15 degs. I do want to plasterboard it and I want to add noggins for this also.

 

[motorbiking]

Ok - I'm no structural engineer, but a couple of observations.

- Light, have you covered the roof up to see how much light you are going to lose going for the solid roof?
- spacing, you'll need quite a bit of timber to cover the plaster board spacing.
- the side walls are solid brick, but what kind of lintel is over the patio door, how will you stop the roof pushing that out.
- 15 degree tiles are fairly specialist.

Some end beams to make a triangle would make a difference and possibly retro fitting a couple of tie bar cables.

 

[mark2011]

Thanks for the reply.

I want it to be more of a cosy living room than a conservatory so I'd prefer less light. I've put cardboard up to block the sun to give us an idea.

It will take a lot of timber. I'm hoping that this makes the structure much more rigid by doing so. I'm wanting to use sturdy 45 x 70mm noggins but that won't help weight.

There is a thick wooden joist running above the upvc windows at the front. I'll double check how this is secured at either end as I hadn't considered the frame being pushed out.

I'm hoping to use metrotile which states that it can be used on a roof down to 15 degs. I hope that this is true.

 

[motorbiking]

Its the outward forces of the roof that you need to consider, though the house wall helps..

You can buy tie wire kits fairly cheaply - alternatively if your extra timbers can be secured to the wall and beam above the door, then the timber acts as a tie bar.

I'd mentally work out the weight difference of as is and to be and if you are adding more than say 80-100kg I'd add something to retain it and also make sure its supported when you are standing on it.

 

[mark2011]

Will do. Thanks for your assistance. I'll reconfigure my planned noggin pattern to add 3 full length timber beams from the house all the way to the front wall on the back of this discussion. That should help keep it all in place.

Still can't find this TB045 though ha ha.

 

[motorbiking]

oh yeah sorry it was TB4045 and TB4040

 

[mark2011]

No problem. I don't need any digger parts at this moment in time ha

 

[motorbiking]

don't forget lights - now is the chance to think about any cabling in the roof which may be needed.

 

[mark2011]

Yeah thanks. Due to it being a sloped roof then I don't think ceiling light will be practical. It's an art deco style house so spot light will look out of place. We're thinking of having wall lights instead. Although I am very tempted to have speakers in the roof. Very art deco.

Just out of interest, do you staple or use galvanised clout nails on your membrane?

Cheers