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  1.  
    A beginner(me) needs some help to figure this out which is probably second nature to many of you

    We intend to use 100mm celotex to internally insulate inner leaf of cavity wall which is made of 1980’s breeze block made using coal slagg.

    WE’re intending to use the warm batten method of temporarily sticking celotex to wall, taping joints, then applying treated batten to the surface to hold the PIR in position and then fixing plasterboard to the batten with service void behind.

    Where the kitchen units would be fixed we would have more batten or larger pieces of wood to take the strain.

    1) What fixings are good and strong to use through the batten, PIR and into the breeze block?
    2) How far into the breeze block must they go to be strong enough to take the weight of kitchen cabinets etc
    3) What is the placement and number of these screws per PIR sheet
    4) When the plasterboard is fixed to the batten, will the screws stay in the batten or go through to the insulation also?

    Thanks for any help
    • CommentAuthorCharli
    • CommentTimeDec 22nd 2017
     
    Consider fixing a sheet of plywood or osb on your battens, behind the plasterboard- makes fixing kitchen cupboards a billion time easier- you only need short screws to hit the ply and don't have to try and aim at smaller bits of wood!
    • CommentAuthortony
    • CommentTimeDec 22nd 2017
     
    +1 or put a piece of 4x1 behind the wall unit hangers, vertical battens at 600c/c tight under it,

    screws should go 50mm into the blocks which should be parge coated first for air tightness reasons
  2.  
    Make sure that the battens are resting firmly on the floor (vertical battens of course) so that there is no shear load on the fixings. If you put sheet material behind the plaster board (PB) then you will need to rebate the battens to maintain a flat surface.
    For fixings look at this type (hammerfix)
    https://www.screwfix.com/c/screws-nails-fixings/frame-hammer-fixings/cat840010
    They only grip on about the first 5cm so it depends on the quality of your blocks. They don't work too well on soft /lightweight blocks or blocks with voids in them - but then nothing does! The spacing depends upon the grip the fixings get into the wall blocks but if the battens are firmly on the floor then the weight is carried by the floor and not the fixings (OK a bit of rotational force from the cupboards but not much). Whilst they only grip on the first 5cm it helps to get slightly longer fixings to be able to put the 5cm a bit deeper into the block. Accurate depth drilling is essential and I have found that there is better grip if the hammer action is turned off (if you can get the drill into the block like that) as you get a more accurate diameter hole drilled.

    When fixing the PB you only need PB screws long enough the go into the batten, so if you are using 3cm x 5cm roof tile battens (cheap and standard over here) and 12mm PB then 35mm PB screws should be fine. Use a PB screw driver bit in the electric drill/screw driver to avoid tearing the paper on the PB by going too deep
    • CommentAuthorkayserasera
    • CommentTimeDec 22nd 2017 edited
     
    Thanks for the excellent tips everyone. Peter thanks for going into that amount of detail.

    Tony; please explain about parge coating; surely if any water vapour does get into insulation behind VCL it is better to leave it to go through the wall into the cavity. Won't parging the inner leaf stop any vapour escaping and making it more likely to condense on the inner leaf?

    Or does it just make it airtight and still permeable to water vapour ?

    Does it have anything to do with it being breeze block in particular?

    this vapour stuff is confusing me
  3.  
    Charli
    good tip about OSB for kitchen units

    So when you use OSB sheets, you do not bother to plasterboard over it ?
  4.  
    Parge coat is mainly for air-tightness. Yes, it should be breathable (for WV) and air-tight.
    •  
      CommentAuthordjh
    • CommentTimeDec 22nd 2017 edited
     
    Posted By: kayseraseraSo when you use OSB sheets, you do not bother to plasterboard over it ?

    Usually you do plasterboard over it, for appearance and fire reseistance. The OSB simply provides greater strength to hang heavy cupboards etc off the wall.

    I don't understand Peter's comment about rebating battens. I'm not sure what he thinks needs rebating, or indeed why anything would need rebating as a result of a sheet of OSB behind the plasterboard?
    • CommentAuthorFred56
    • CommentTimeDec 22nd 2017
     
    I've done this job a few times. I use concrete screws to fix the battens, a bit like a big self tapper for concrete . There is no plug with those and the fixing is strong. Don't use an impact driver when screwing them in. Make sure all the perimeter of the insulation is sealed as well as taping all joints. I run a horizontal batten top and bottom and then verticals. As Pete in Hungary says, rest the battens on the bottom to cancel the reactions. I like to have all the board edges supported. If you have the top of your floor membrane sticking up, trap it between the bottom batten and the face of the insulation board. A good sealing compound for non-absorbant surfaces like foil and plastic is Hodgsons Seam Seal. It's very cheap if you buy it by the case. Intended for the caravan manufacturing industry for sealing seams. I have a couple of tubes in my garage if you live down my way in east Cornwall.
    Another handy trick is self adhesive cable tie bases to help hold the cables in place. Make sure you wipe the surface of the foil before trying to stick them on. The foil face of the insulation seems to grab dust through static charge, a fist full of tissue soaked in meths works well.
    I use Fermacell instead of plasterboard in kitchen and bathrooms. It's the same thickness and you can screw your kitchen cabinets directly to it. Removes the need to mess about with OSB, ply or extra bearers. Basins and the like are heavy and still need extra support though.
    Few tradesmen are familiar with Fermacell so expect them to whinge and try to stuff it up. It also weighs about 40kg a sheet and if you are small like me, it's a bit of a strain.
    • CommentAuthorBeau
    • CommentTimeDec 23rd 2017
     
    Posted By: CharliConsider fixing a sheet of plywood or osb on your battens, behind the plasterboard- makes fixing kitchen cupboards a billion time easier- you only need short screws to hit the ply and don't have to try and aim at smaller bits of wood!


    Thats what we did just OSB instead of ply.
  5.  
    Posted By: djhI don't understand Peter's comment about rebating battens. I'm not sure what he thinks needs rebating, or indeed why anything would need rebating as a result of a sheet of OSB behind the plasterboard?

    If you fix the battens to the wall providing a nice flat surface to take the plasterboard and then screw a sheet of 10mm or 12mm OSB to it then without the rebate the plasterboard will step out 10mm or 12mm and you will have lost your nice flat wall. I assume the OSB will only be at the location of the cupboards and not over the whole wall.
    • CommentAuthorkayserasera
    • CommentTimeDec 23rd 2017 edited
     
    Posted By: Peter_in_Hungary
    Posted By: djhI don't understand Peter's comment about rebating battens. I'm not sure what he thinks needs rebating, or indeed why anything would need rebating as a result of a sheet of OSB behind the plasterboard?

    If you fix the battens to the wall providing a nice flat surface to take the plasterboard and then screw a sheet of 10mm or 12mm OSB to it then without the rebate the plasterboard will step out 10mm or 12mm and you will have lost your nice flat wall. I assume the OSB will only be at the location of the cupboards and not over the whole wall.


    yes that is whay i questioned the need to plasterboard over the OSB, because of extra projection into room otherwise unless the whole wall is OSB'd, or am i missing something ?
    OSB without PB could be hidden by the cabinets anyway ??
  6.  
    Posted By: Nick ParsonsParge coat is mainly for air-tightness. Yes, it should be breathable (for WV) and air-tight.


    Thanks then to tony for drawing parge coats to my attention as seems it can make an important difference to insulation properties of the wall:bigsmile:
    • CommentAuthorkayserasera
    • CommentTimeDec 23rd 2017 edited
     
    Great detail in your post Fred thanks

    regarding femacell which is quite heavy in addiction to the kitchen cabinets; Will it all be supported OK ??

    Is the firmcell fitted right down to the floor so it rests on it ?
  7.  
    djh said: ''I don't understand Peter's comment about rebating battens. I'm not sure what he thinks needs rebating, or indeed why anything would need rebating as a result of a sheet of OSB behind the plasterboard?''

    I think it's because Charli said: ''Consider fixing a sheet of plywood or osb *on your battens* (my asterisks for emphasis).

    I assume djh, like me, assumed that where a piece of OSB is inserted for strength, it is, for that area, *instead of*, rather than on top of, the battens.
  8.  
    Clear point nick

    So OSB off or on battens is OK then ...
    •  
      CommentAuthordjh
    • CommentTimeDec 23rd 2017
     
    I put OSB over the whole wall on battens and then plasterboard over the top. The idea is that you don't have to worry about where the cupboards are going, or worry about changing your mind or worry about what happens when somebody wants to replace the kitchen with a different design. And nor do you have to worry about getting rebates to the exact depth. You don't want to just put OSB up because the plasterboard provides the fire resistance.
  9.  
    OSB over the whole wall makes sense rather than just for the cupboard area which is what I had assumed.

    +1 for the PB over the OSB

    Oh and I would also use battens to keep the service void
    • CommentAuthorFred56
    • CommentTimeDec 24th 2017
     
    Kayserasera - ref you point about the weight of the Fermacell and kitchen. If you fix the battens securely and make sure the battens rest on the floor the forces are transfered to the floor rather than the batten fixings. Make sure you fix the Fermacell to the spec . I have been doing this for years and it has not failed yet.

    With a wonky wall i have set the whole of the lining off the masonry using gypliner. If you look up drylining metal profiles you will find all the manufacturers make a lightweight steel system for this purpose. I did a big barn conversion like that in 2003. I live there for several years and it never failed. I saw an excellent system like that being installed on some apartments in France in 2015. It had the added feature of adjustable plastic legs to accurate set the inner steel track vertical and aligned. They were builing the external leaf in cast insitu concrete and insulating internally with about 200mm of a dense mineral wool. The track system allowed them an easy way of lining. Quality of their work was excellent. They also had the best metal casement windows I have ever seen.
  10.  
    There may be considerable benefit from a collated screwdriver.

    I bought an excellent 2nd Sennco hand one plus drill driver from eBay for just over £100.

    F
    • CommentAuthorCharli
    • CommentTimeDec 28th 2017 edited
     
    Posted By: kayseraseraCharli
    good tip about OSB for kitchen units

    So when you use OSB sheets, you do not bother to plasterboard over it ?


    I actually did the 'aim really long screws at tiny battens hidden behind loads of internal insulation' trick- but I really don't recommend it! For the bathroom we did sheets of ply, then sheets of plasterboard- much easier to attach cupboards to!
  11.  
    Posted By: CharliI actually did the 'aim really long screws at tiny battens hidden behind loads of internal insulation' trick- but I really don't recommend it!

    The proposal here is to have the battens on top of the insulation and a service void between the insulation and the OSB/PB. This should make the 'aiming' of the screws easier and the inclusion of OSB remove the need to aim at all.
    What thickness of OSB is recommended in this situation ?
    •  
      CommentAuthordjh
    • CommentTimeDec 28th 2017
     
    Posted By: Peter_in_HungaryWhat thickness of OSB is recommended in this situation?

    I used 18 mm, but that was because I used 18 mm for everything*. It's easier to manage stock of a single thickness. I expect thinner would work but I've no idea how thick.

    * except flooring, that was 22 mm T&G.
  12.  
    I'm trying to find screws that are strong and long enough to go though 25mm batten, 100mm PIR and into the wall

    http://www.thorhelical.com/insulation-fixings/fixing-insulation-to-walls/

    These fixings only go up to 150mm long. That means less than 25mm can go into wall. that doesn't seem deep enough.

    Can anyone suggest other fixings i could use to do the warm batten method ?

    otherwise I will have to think again :(
    • CommentAuthorDarylP
    • CommentTimeJan 2nd 2018
     
    Try https://www.twistfix.co.uk/warm-roof-fixings-super-7
    Cheers:smile:
    • CommentAuthortony
    • CommentTimeJan 2nd 2018
     
    I wold say yes, prefer 30mm and this could be achieved by countersinking the battens by 10mm. Use new masonry bit, long series, I would drill only gently, ie not on hammer or percussion, use 5.5mm and red plugs

    I hate those twisty things, ok wood to wood
  13.  
    Posted By: DarylPTry https://www.twistfix.co.uk/warm-roof-fixings-super-7


    those come in much longer sizes thanks.
    Are they ok for masonry too? the blurb talks about using for wood.
  14.  
    Posted By: tonyI wold say yes, prefer 30mm and this could be achieved by countersinking the battens by 10mm. Use new masonry bit, long series, I would drill only gently, ie not on hammer or percussion, use 5.5mm and red plugs

    I hate those twisty things, ok wood to wood


    Thanks.
    So do you mean you think that a minimum of 30mm of screw is required into the blockwork. You would use a 5.5mm diameter guage masonry bit? The red plugs is the type of rawlplugs ? Are we still talking about twisty things or another type of screw, cos you hate them so much ?
    Sorry to be slow, but don't want to make mistakes.
    • CommentAuthortony
    • CommentTimeJan 2nd 2018
     
    Yes, min 30mm into blocks. Red plugs suit 5.5mm holes, using hammer drill will make holes too big, don’t use twisty things, use screws or decking screws etc
  15.  
    How about these ones ? They don't need plugs

    https://www.screwfix.com/p/easydrive-countersunk-concrete-screws-7-5-x-180mm-100-pack/9569h

    How many per length of batten do you think?

    Batten spacing ?

    Thanks!
   
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