Can I temporarily insulate a conservatory roof?

Oh!! forgot to add - think I will just go with the larger 4x2 joist - was even looking at 5x2 ??
Regards

 

A 'purlin' is a joist which usually runs at right angles to roof rafters and is usually supported by vertical struts (which could be part of a low wall). This gives the long length of a sloping roof rafter a further brace in the middle.

So, what I'm 'suggesting' is, if you could mount and support (perhaps from hangers from the apex) a 4x2 horizontally in the middle of where the new ceiling is gonna go, and at right-angles to the new joists, then your new ceiling joists could be reduced to 3x2s as they'd be screwed up into this 'purlin' and supported in their middles. It's chust an idea - I'm not suggesting you do it.

Hmm, so you have horizontal tie-bars running across your current roof? And you are gonna whip them out?

Cough.

Man, you are gonna have to post some photos on here so's we can have a look-see...

(Your 'span' comments - I'm afraid I don't understand them. You are building a 'ceiling' not a roof. Slope regulations just don't apply - you can make your ceiling any bludy shape or slope you want...)

5x2? Jeepers. If you can tell us what span your new joists will be, we can advise on joist size.

 

Ah! Sorry - I just got your 'span' comment.

Hmm - good point. Yes, you'd expect joist (and rafter) spacings to be 24" (600mm).

Ok, don't worry about this from a strength point of view, as we are only talking about holding up a ceiling, and a very small one at that! However, you may need to ensure that the 30" spacings will suit the size of board you will be using - where sheets join together, there must be a timber noggin or joist. (You'll notice that 600mm (24") suits standard p'board sizes perfectly)

How many joists will there be, then, in your whole new roof? (Ie: how many roof rails at 30" spacings are there?)

In theory you don't even have to mount your joists where these roof ali bars are - you can make your ceiling framework completely self-supporting, and mounted up from the timber 'wallplate' you'll be fitting first. So, you could make it 24" if you wanted to. There is no one 'answer' here - diff peeps will do it diff ways. (What has Ged done?)

As for the TLB, if the 27mm thick is just as good thermally as the 40mm stuff, then use - whichever one you want .

 

DA
I have downloaded some photos (took me ages to find out how)
I reckon 6 vertical struts/joists (side to side)
Looks to me that Ged ran his from the gable (as you say must have made his pitch to suit the board)
Must try again with photos

 

Guess what will happen if you remove that tie?

(snigger...)

 

Will the new roof fixtures not replace the function of the tie-bars?
The tie-bars are presently extremely loose with next to no tension on them

 

To be honest, I don't know how much use - in practice - these are, or how much decorative. However, I suspect they were designed to perform a function, and that's to prevent the sides of your connie bowing outwards under the weight of the roof (to stop the 'A' shape of the roof bars from splaying outwards under its own weight - like a stepladder with no, er, 'tie').

In theory, yes, your new structure would replicate this function, but only if the joists were properly secured to the connie sides. I'm sure, again in practice, that 4 or 5 4x2s spanning across will more than do the job, but do bear in mind the joists won't be going across at the 'wallplate' height, but a bit up the slope. How well fixed will they be to the roof side rails?

Basically, it wouldn't be right for me to suggest a solution as I'm an amateur... There, you made me confess .

(That tie may well feel 'loose', but I wonder how it reacted to the gales last night? It may well have been quite 'tight' in these gusts...)

 

hmm!!!
OK DA fully understood
I do feel that I can more than adequately substitute this bar by tying and strapping the 4x2 joints to the conservative wallplate thus ensuring cross rigidity
To be honest it may function as you have described - sure it must be there for this reason - but since we had the conservative built (approx. 6 years ago) I have never seen it under any strain
Just seems to hang about like a limp '**'
Nevertheless Let me think about it
Thanks as always for your professional thinking

 

DA
Sorry to come back so quickly but since reading your last thread again I have noticed that the horizontal tie bar is actually attached to one of the vertical struts on the poly roof and not the wallplate as such (about 6" up from the top of the wall plate)
Regards

 

That's all well and good, but I'm still an amateur so cannot comment

 

Basically, I'm not going to say 'yeah I'm sure it'll be fine - go ahead'. Am I?

 

No worries DA
I will make a management decision to continue with my objective
Kind Regards
Onwards and Forward

 

Cool - keep us posted.

If your connie sides have continuous lengths of sturdy ali section running along the top of the windows where your wallplate will go (and it looks as tho' they do), then I can't see much being able to splay your sides apart.

(If the window sections were completely separate without a box-section tying them together along the top, then possibly there would be more potential for them to bend at their vertical joins and allow the top to bow out.)

However, I'd like to hear other peeps' comments on these tie bars.

 

Its strange that the tie-bar is only fixed to one rafter as opposed to the wallplate, it's relying on the one rafter to be fixed really well if the windows did start to bow out, (which is highly unlikely under normal useage)

 

it's only a poly roof so not a great loading on it - handy for hanging the tinsel off at xmas

 

I understand that, though covered in snow wound be a lot heavier, I suppose it where it is for height proposes so tall bugger like me don't bang our heads,

 

Bjp, the tie is there to replicate the job of ceiling joists in your home - they tie the splayed ends of the roof rafters together to prevent them from, er, splaying. (Also in a house roof you'll get the strut/tie going across further up - the '-' bit in 'A'.
I'm guessing that last bit in compression?)

Obviously a roof house is a different kettle of worms, having tons of tiles sitting on it.

So... it's gamble.

Would I whip it out if this was my connie and feel ok about the new ceiling doing the job instead? Yep .

 

Aye DA - I feel OK about taking it off - as long as I have a number of joists in place before I do so
I am gonna quantify and order the timber requirements today
In for a penny in for a pound!!
Regards

 

Don't forget the photo record.

(Readers of this thread need a 'how not to do it' version too... )




Yanking your chain

 

No problems will do