Double layer Fireline board

[craftycarper]

Hi everyone,

Been using this forum at various times in the past and found it very helpful. Only just registered today as I need some advice, so this is my first post. Hope I am posting in the correct section.

We had the asbestos ceiling in our garage professionally removed a short while back and I am about to renew it. There are 2 bedrooms over the garage, so I know that it needs to be replaced with fire protection board.
I called British Gypsum Tech Support today and they were quite helpful.
I was hoping that they did a board that had both fire protection and insulation properties, but unfortunately they do not.
I was told that both 12mm and 15mm Fireline was 30 minute rated, which I suspected, so am looking at fixing a double layer. This will give me 1 hour rating.
The garage is 8M x 2.45M and I know that I have to offset all the joints. The spacing between the joists in 370mm and they run width ways. I was told that the fixing centres should be 230mm centres.
1) Can I get away with using 370mm centres going lengthways? I hope so as the original timbers are on joist hangers.
2) Can I screw through both boards rather than fixing the first board seperately? If so, what size screws would I need?
I'm also looking at hiring a panel lifter for the day to make the job that much easier.
Any advice will be greatly appreciated.

 

[PrenticeBoyofDerry]

400mm centres will be okay, that's centre of each joist to joist not the gap between them.
But you said you have had the original removed, what is there there now and why do you wish to alter it?
Or are you using the exsisting joist to fit addition joist to?

I would tack the the first skin of boards on, you don't have screw or nail every 150-200 mm just make sure it is secure, then you can fix the second skin up. I would use 65mm screw for the double layer of boards and 40's for first.
You could make a couple these to save hire charges
http://wiki.diyfaq.org.uk/index.php?title=Dead_man_prop
and stagger you joints as
http://www.zurich.co.uk/NR/rdonlyre...DE0F7CFBC0/0/PlasterboardCeiling107782A02.pdf

 

[craftycarper]

Thanks for the very prompt reply.
We had the ceiling removed when we had an extension built across the back of the garage last year. At some point, during previous works before we owned the property, the ceiling board had been cut to take CH and water supply pipework - some of which ran about a foot above the whole length of the garage floor! I needed to change this and was not prepared to risk cutting the board further as the building survey had already identified this as asbestos. There is currently no ceiling in place and I intend to renew asap.
The "deadmans prop" could work, but it would still mean getting the board up to ceiling height - may look into this further.
Looking at your other link, I am now wondering if I should put noggins all round the perimeter to support the board at the edges.
I am only thinking of a plaster skim finish -it is only a garage after all- and the original ceiling was pretty secure and only nailed in situ.

 

[PrenticeBoyofDerry]

If you are only boarding and plastering the ceiling out, it would be a good idea to put noggins in around the perimeter, normally when plasterboard and plastering the walls of the room get done too.
This helps to support the ceiling boards and prevent them sagging around the edges.
So if you are not doing the garage walls fix in noggins.
Usually when I do ceilings I like to use 2400x1200, this means I can cover a large and small areas, quite quickly and reduce the number of joints in the ceilings. If the floor to ceiling height is not excessive, I have always used deadmans props, it will be handy to have a spare pair of hands, but they are an extremely useful tool.
I normally work off a platform that allows me enough headroom under ceiling, normally just enough so I can pop the board over my head and the board be tight to the ceiling.
If there are two of you it is not a complicated procedure once you have the knack of swinging the board over your heads.
I'm a bit old school, so forgive me if you think I am not following any strict H&S policies for working at heights, I will say I have never once injured myself doing this and I have put a lot of ceilings up on my own using 2400x1200mm. But I would advise a help being at hand.

 

[craftycarper]

Re noggins - I understand what you are saying and looks like I will have to do this first. Extra work for me, but I do want to do it right.
I am not gonna board out the walls, so it seems the sensible thing to do.
This is gonna end up being a bit of a longer term project and will end up with a total garage refurb as I also need to: get the brickwork repointed in various areas, insulate the back wall with 65mm board, alter a lot of the electrics to upstairs rooms and incorporate the garage, move a joint in a soil stack pipe - if possible, raise a drain cover and relay the concrete floor. Doesn't help that I have heaps of stuff in the garage at the mo' either as it is used as a workshop.
Maybe I should put up some photo's as I progress? This is defo gonna be a long term job though, as I have plenty of other stuff to do, but ghetting the ceiling is key.
Found this yesterday and thought it was just the job! http://www.youtube.com/watch?v=TkrRblKLvJw

 

[PrenticeBoyofDerry]

The one man is very invented
Good luck with your project, I'll keep a look out for your progress reports and if in the mean time you need any helpful advise and I am able to do so I will gladly help.
If you have electric cables in the ceiling void and you are insulation it, you will need to either make sure the cables are secured or run in a method that will allow the current to run safely and not over heat the cables.
There are factors/calculations for de-rating cables in insulation and you could quite easily lose 50% of the cables rating, if it is totally surrounded by thermal insulation along it's run.
There are number of ways around this, using different installation methods or upgrading the cable size.
It is normally the power circuits that incur this problem, lighting circuits that are on 5A fuse or 6A MCB are usually fine as the cable size for lighting is generally 1.00 or 1.5mm T&E and this can be de-rated by 50% and still safely carry 5 or 6Amps.
But socket , shower, cooker circuits are a different animal.
So if your starting as a new project now is a good time to be thinking about the design of these circuits or employing someone who can.

 

[craftycarper]

I did consider 35mm insulation fill between the joists, but decided against it due to electric's and the need to alter them. That was the reason why I phoned BG in the first place, to see if there was a combi type fire retardant board with better insulation properties. I was told there was nothing like this available, hence the choice for a double layer of Fireline + better fire rating.
I'm really gonna have my work cut out on the noggin front all round the perimeter as I think I counted 27 joists from front to back. And joist hangers will mean they won't get fixed right at the very edge either.
Still in the process of clearing/selling off small engines, mowers, genny's etc. that are preventing me making a start. Will endeavour to get some early stage photo's on though.
Just read through some other threads re plasterboarding ceilings and advice seems contrary on a lot of items. However, with a double layer meaning additional weight, not boarding out the walls, perimeter noggins it must be I suppose. Will probably need to fit down the middle as well to pickup the other edges.

 

[craftycarper]

Cleared one half of the garage now and just had the back wall and some other areas in the garage repointed. Getting prepp'd to start mounting some board soon.
However, despite the fact that I take on board everything that "Prentice" has said, I am still very much in 2 minds as to fit additional noggins or not.
There has been contrary opinion on this subject in other threads and now my builder has said he doesn't think it will be neccessary with x2 12.5mm board at 370mm centres. Would just like someone to post a bit of opinion before I go out and buy the timber to do this, as now I really don't know if this is neccessary or not. (no offence "Prentice")
If I do go ahead, the only way I can see to get close enough to the board edges would be to screw battens on the walls instead of noggins to joists.

 

[PrenticeBoyofDerry]

craftycarper, No worries I'm not offended try your bl00dy best and some ig*%@%"T C@%%Ts have no firking @%%%**
My advise was purely belt and braces and what I would do in your position, if time and money is an issue, you should have little problems, taking in to consideration the use of 12.5mm boards and joist centres of 400mm.
But if others wish to offer additional advise that differs from mine, I would not be offended.