kingspan or celotex

GClyde

ds1980, a wee tip for you.....

Some folk place a layer of chipboard behind the plasterboard so that they can get a good fixing for kitchen wall units etc.

Graham

typeractive

ds1980 wrote: »

Just seen the post finally took off! I actually got some seconds 25mm boards from secondsandco came in at about £10 a 1200x2400 sheet.

They were very easy to deal with. Have gone the battening, then insulation and plasterboard on top route. Same will apply for the ceiling. Forget the laminate stuff with integral plasterboard twice as expensive.

So, what you're saying is rather than buying an insulation board with the plasterboard bonded onto it, you bought both separately then; installed the insulation between your battens, and then plasterboarded straight on top?

If that is correct it's funny you mention that as it was going to be my next question to Graham (and anyone else) - can this be done? My original rafters were 75mm by 50mm 3" by 2" (approx). I have had to build these rafters up to allow for the free flow of air in there (as shown in my little sketch above).

So - I can put in some 50mm insulation between the rafters now. These should sit flush. Can I then 'stick' / attach the further 65mm onto the inner insulation, and then attach 'normal' 12.5mm plasterboard onto the inuslation? Could this be dot and dabbed onto the insulation?

Whilst the specs suggest to use Kingspan or Celotex, these are surely only brands. The main concern would be getting the correct thicknesses of insulation? My worry would be the weight of the plasterboard with skim weighing onto the 'inner' insulation.

I know this route would work out a spot cheaper for me, and I won't be as precious in making any errors (which I've made many recently!! :rotfl:)

Graham - I apologise for asking all these questions though you are VERY helpful, and I appreciate the help!!

Thank you!!
:beer::beer:

GClyde

There is nothing wrong with using seperate layers. Although, if you do, then you must make sure that you prevent vapour/moisture getting to the fabric. hence, my suggestion of adding a vcl directly behind the plasterboard, and making sure taht all gaps are sealed.

You can put insulation between the rafters and on the underside of them, as long as you maintain a 50mm ventilated air gap on the cold side for ventilation purposes. You should also make sure that you are not reducing head height over stairs/landings when adding more insulation to the underside of rafters. As this could be construde as making matters worse and contravene building regs.

Graham

typeractive

GClyde wrote: »

There is nothing wrong with using seperate layers. Although, if you do, then you must make sure that you prevent vapour/moisture getting to the fabric. hence, my suggestion of adding a vcl directly behind the plasterboard, and making sure taht all gaps are sealed.

Right - I got ya! I was getting confused with having a VCL AND the 'special plasterboard' hehe.

New diagram for you to help visualise (though it's late and I'm tired so it's a bit raggy!)



So, you can see my:
Built up rafters to 100mm thich.
Inbetween I have the 50mm foil insulated board (giving a 50mm air gap).
Then on top I will screw the thicker foiled insulation (65mm) onto the rafters (being careful not to hit the already new screws! eeek
Then (if I have this correct) my VCL. What material should I buy for this? I was thinking I could staple gun this on perhaps?
Finally screwing my 12.5mm plasterboards into th thicker foiled insulation.
Skim on top.

Wow - that's a lot! I wonder if it will work out I'm saving that much cash overall, for the amount of work? hmmm Chepest quote for celotex so far is £530 to cover 40sqmt. This would need to be fastened somehow anyway.

Do I have the VCL in the correct area? As it might be easier to pin that in between the 2 insulation boards?

You can put insulation between the rafters and on the underside of them, as long as you maintain a 50mm ventilated air gap on the cold side for ventilation purposes. You should also make sure that you are not reducing head height over stairs/landings when adding more insulation to the underside of rafters. As this could be construde as making matters worse and contravene building regs.

Graham

Yes - head height has been a worry. I think we can JUST get away with it for the door purposes. The building control officer - very much unlike your goodself seemed pleased about this - no joke. When my planner put in the plans for proposal, he asked "why does he want an en-suite in a terrace?" Apparently he is just mean to everyone and has never ever said if someone has done a nice job etc. The good thing is though - he passed the plans on the basis of the head height being ok (which we think should be). I'm positive I read/heard that a door can have a sloping edge above it of approx 100mm (which I might need - but the new stoothing will soon dictate that for us).

If this method of layering up the insulation and plasterboard is feasible then I think we could go for this! Also means less of a worry for my electrician making a mess of any of the boards! :eek:

Cheers Graham!!!!!! :A

GClyde

Good morning typeractive..your sketch looks brilliant, well done :T

You've got everything in the right place too

I could do a U value calculation for you if you like, if so, then can you confirm depth of the original rafter.

With regard to the foil backed insulation, this acts as a reflective vcl, however, in order to get the full benefit of this property then all joints need to be sealed to prevent vapour migration - and it's far from being ideal, as vapour could pass through the timbers either side of the foil backed insulation.

Therefore, the best option is to use 500 guage polythene as the vcl. All you need to worry about is to overlap the poly and tape the joints. You must take extra care not to puncture the vcl with services etc.

It is also worthy to note that you may need to consider introducing more back ground ventilation in the way of trickle vents to allow any build up of vapour within to be replaced with fresh air.

Again, best of luck and i hope this helps :j

Graham

typeractive

GClyde wrote: »

Good morning typeractive..your sketch looks brilliant, well done :T

You've got everything in the right place too

Thanks - I really prefer to describe things with pictures as I *ALWAYS* get the wrong end of the stick otherwise. I'm a visual learner! hehe

I could do a U value calculation for you if you like, if so, then can you confirm depth of the original rafter.

That would be cool...or perhaps warm? heheh. The original rafters were 75mm. The area to cover is 40sqmtr (that is the entire roof space - not just the attic room if that makes sense?

With regard to the foil backed insulation, this acts as a reflective vcl, however, in order to get the full benefit of this property then all joints need to be sealed to prevent vapour migration - and it's far from being ideal, as vapour could pass through the timbers either side of the foil backed insulation.

Therefore, the best option is to use 500 guage polythene as the vcl. All you need to worry about is to overlap the poly and tape the joints. You must take extra care not to puncture the vcl with services etc.

Right - when I first read this I was worried as it sounds very delicate. Though upon second reading it doesn't sound too bad.

Am I ok to use a staple gun to pin the 500 guage sheeting up? What would the sheeting be called? i.e. what do I ask fro at the builders merchants? (yes I look like I know what I'm talking about with my drawings etc, but when it comes to the finer details I always muck up!)

Should I use duct tape to tape up?

Will I be ok to screw the plasterboard into the insulation board?

As for services etc, I'm thinking I should maybe get the first lot of insulation in, to allow the electrician in, then I could put the extra layers on top once he has been. The plumber will need access through the floor I imagine, so he won't be wrecking the walls.

It is also worthy to note that you may need to consider introducing more back ground ventilation in the way of trickle vents to allow any build up of vapour within to be replaced with fresh air.

Again, best of luck and i hope this helps :j

Graham

Trickle vents...right, what on earth are these then! heheh I'll have to look into these. Can these trickle vents and ridge tiles be installed after the insulation has gone in?...I'm guessing the trickle vents will need to go in first? Hopefully the ridge tiles are a separate entity and can be done from the outside when my builder gets up on the roof to sort out some of my newly found leaks! :eek:

I want to make sure that I can get everything done in the correct order as I don't want to have to install these extras after the insulation is cut to size and installed etc!

**quick note, whilst Graham is kindly helping me/us, it should be noted that anyone wishing to follow this advice should check with their local planner / building control officer to ensure these measures will meet requirements**

Cheers Graham (again)...you're building a lot of thanks in posts from just me!!! heheheheh :rotfl: :T

GClyde

Great, I agree a picture tells a good story

Using a staple gun is fine, just make sure that any rips are taped over....duck tape would be ideal too

'Will I be ok to screw the plasterboard into the insulation board?'......yeup, the screws can go through the plasterboard + insulation into the timbers.

'As for services etc, I'm thinking I should maybe get the first lot of insulation in, to allow the electrician in, then I could put the extra layers on top once he has been. The plumber will need access through the floor I imagine, so he won't be wrecking the walls.'...............Right oh, so do you intend creating a gap/service void?...If so, then I'd recommend creating a service void directly behind the plasterboad, and not have any cables touching the insulation.

Trickle vents...right, what on earth are these then! heheh I'll have to look into these. Can these trickle vents and ridge tiles be installed after the insulation has gone in?...I'm guessing the trickle vents will need to go in first? Hopefully the ridge tiles are a separate entity and can be done from the outside when my builder gets up on the roof to sort out some of my newly found leaks! :eek:

hahaha.........trickle vents are small manually controlled vents that go in the top of windows to allow slight air movement/changes.

**quick note, whilst Graham is kindly helping me/us, it should be noted that anyone wishing to follow this advice should check with their local planner / building control officer to ensure these measures will meet requirements** ...thanks for the support here, I agree, folk need to make the necessary checks first before doing anything.:D

Cheers
:beer:

typeractive

GClyde wrote: »

Great, I agree a picture tells a good story

Using a staple gun is fine, just make sure that any rips are taped over....duck tape would be ideal too

'Will I be ok to screw the plasterboard into the insulation board?'......yeup, the screws can go through the plasterboard + insulation into the timbers.

Would it not be easier to screw the insulation onto the timbers, and then the plasterboard onto the insulation? Or perhaps this is not the most 'grip effective'? Whilst it's more work - it's more manageable for beginners.

Right oh, so do you intend creating a gap/service void?...If so, then I'd recommend creating a service void directly behind the plasterboad, and not have any cables touching the insulation.

Yes - like this:




The red lines are to mark the new stud frame under the purlins. I will have some little cupboard spaces in these also. Though just basic. I guess this would be ideal for the electrician to run cables. There is a void from the ceiling also for the recessed lights to go in.

hahaha.........trickle vents are small manually controlled vents that go in the top of windows to allow slight air movement/changes.

Right - I'm just in the process of ordering my Velux windows. Can I add these onto the windows later or will they already be installed into the windows?

Cheers - oh any idea on the name of this polythene 500 guage stuff?!
:beer:

GClyde

I think that as long as all the components are secured back to the timbers then you should be fine.

The red lines are to mark the new stud frame under the purlins. I will have some little cupboard spaces in these also. Though just basic. I guess this would be ideal for the electrician to run cables. There is a void from the ceiling also for the recessed lights to go in. ...Ahh...you mean the cables and pipes will go into the roof void behind the oxters/hanging posts....now I am with you. I thought you meant sandwiching them between the insulation and plasterboard

Trickle vents for the velux rooflights should come as standard..worth checking though. It's best to have them factory fitted....saves drilling holes/long slot at the top of the window.

With regards to the poly stuff, visqueen comes to mind, but there will be other makes out there. Just ask the builder merchant for 500 guage polythene vapour barrier...he will know what you mean.

Rememebr, the vcl will need to go on the vertical oxter/hanging post as well as the sloping ceiling.

By the way, the U value for your roof comes out at 0.21...which is good. :T

Here, how'd you manage to add the sketch to the post?........I'm stumped as to how it's done

All the best

Graham

typeractive

GClyde wrote: »

I think that as long as all the components are secured back to the timbers then you should be fine.

Cool!

...Ahh...you mean the cables and pipes will go into the roof void behind the oxters/hanging posts....now I am with you. I thought you meant sandwiching them between the insulation and plasterboard

Yeah, they will be too difficult to get under the secondary (lower purlins), so bringing the wall down vertical will make the room a bit more practical. Plus it will be nice to have some built in cupboards for hiding things like Christmas trees! hehe Initially though I was thinking of sandwiching them...until it dawned on me!

Trickle vents for the velux rooflights should come as standard..worth checking though. It's best to have them factory fitted....saves drilling holes/long slot at the top of the window.

Right. Well I've just ordered my velux's! maybe slightly too late to ask for the holes as I got a good price, and I'm sure they won't be custom produced. I'll get round this worry another time if I need to.

With regards to the poly stuff, visqueen comes to mind, but there will be other makes out there. Just ask the builder merchant for 500 guage polythene vapour barrier...he will know what you mean.

Check!

Rememebr, the vcl will need to go on the vertical oxter/hanging post as well as the sloping ceiling.

Ok...will I also need to insulate between the hanging posts?...I don't think I've allowed for this bit....hmmm. Maybe I can just use the same thickness as between the rafters? 50mm, as opposed to the 50mm plus all the other layers? (please advise this is the case! hahah)

By the way, the U value for your roof comes out at 0.21...which is good. :T

Here, how'd you manage to add the sketch to the post?........I'm stumped as to how it's done

Ah - that would be telling! heheheh. I use a programme called Adobe Illustrator. It's good for drawing vector graphics (that's what they are). It's fiddly to get stuff like the perspective correct - I'm by no means a professional with this package, but I can get by. I find it easier to understand when I can take things apart like that. Once I have drawn it out, I save it just like any other image/photo (.jpg file) and upload it.

If I'm on here at the same time as you, I try to knock out these drawings and pst back between posts. hehehe Feel free to use them if you ever need to describe to other people etc. I like sharing.

Graham, you really are a true gent. I've understood so much more by talking to you on here than I have with my building control officer (who just confused me and my builder more so!) As stated I'm not taking this as your word, though I know it's a feasible argument of meeting the requirements with materials as opposed to having to use branded boards. yes it will be more work to an extent, though I'd imagine the boards will be lighter, easier to chop, less of a worry of making mistakes as it will be more accessible.

More to the North East and be our building inspector!! :rotfl::T

p.s. this U value stuff. Can you give a brief overview of what the scale is e.g. 0.21 being good, what is excellent and what is terrible? I'm guessing the benefits of it being good are keeping the heat in the house etc. This being the case my attic may well turn into a mini sauna as it's alread hot working up in there and I literally don't have ANY form of heating in the house whatsoever...apart from a couple of light bulbs we're using to work with!