Tuesday, 19 June 2012

Battening and insulating the walls

I spent yesterday and today battening the internal walls. The first step was to effectively wrap the walls in a breathable membrane. This would help to prevent condensation forming, however it shouldn't be an issue as I'm using the same 'warm' method used for the ceiling. This will mean there is no air around the wall, thus condensation can not form. To be on the safe side though, the insulation will be sealed in with silver foil tape, preventing any form of air movement.

Once the membrane was up, I started on the stud work.

To get the correct widths, I cut a sheet of Celotex in two lengthways, creating a 600mm width (or near enough to 600mm as the sheets are ever so slightly smaller than that), and basically used it as a guide as to the distance between battens.

Once the vertical battens were in place, I placed a single noggin across the middle of each. 

The same was done for the back wall, the only difference being that smaller gaps were used between the vertical supports. 

For the left hand wall, I opted to use two sets of noggins as this wall will likely have a cupboard on the wall, in addition to monitors mounted on it. Because of this, I've basically strengthened a few parts of it to allow for heavy loads to be supported. 

I've opted not to add the insulation to this wall just yet as the electrics need to be added. I've also not yet sealed the insulation in place yet as I'm waiting for some more silver foil tape to be delivered (damn you eBay!).

Once the walls are sealed up, I'll get the right and back wall covered in plasterboard.

At this point you may notice I'v not talked about the 'front' wall (I.E the wall with the door and window). I had a bit of a problem with this one. The door and window that came with the shed have a 1.5cm frame built into them. The floor bearer does not. Meaning that the roof bearer is 1.5cm out. So I basically need to add a 1.5cm piece of wood across the top, to support the plasterboard. I've actually got a ton of spares from the shed build so hopefully I can find something half decent to use for this. Once that's done I can get that wall insulated and boarded up. Thankfully there will be no major weight load on this wall, just plasterboard, otherwise it could have cause a potentially annoying problem resulting in an odd shaped wall.

Finally, taking the idea from someone else who is currently converting a shed (whom I met via the DiyNot.com forums), I've decided to add a 'lessons learnt' section to each post, basically saying what I screwed up or would do differently next time, so here it is:

Lessons Learnt

  1. Never underestimate the amount of wood and screws you'll need. I did three separate trips back to Wickes to get more supplies!
  2. A staple gun is very helpful when putting up a breathable membrane. You still need to seal it to the wall with a waterproof tape (I opted for duct tape) but it helps hold it in place while you get it all lined up.
  3. Cutting Celotex is a pain. If using a saw, get one with extremely fine teeth. I found a kitchen knife (The kind they use in Subway to cut sandwiches - very sharp!) to generate zero dust, compared to a saw, which got it everywhere!




Stud wall

Messy insulation
The full set of photos so far can be found on the Flickr Page.

The end does seem to be in sight. The main big jobs remaining as of this post are:
  • Seal the insulation on the right and rear wall
  • Sort out the 1.5cm gap on the front wall, and add insulation
  • Plasterboard over the front, right and back wall
  • Get the electrics fitted on the left wall
  • Insulate (and seal) the left wall
  • Plasterboard the right wall
  • Skim over the plasterboard gaps
  • Paint the room
  • Add the flooring
  • Add a skirting board
  • Move in!
Actually, when you put it into a list, there is still a hell of a lot to get done. My feeling is that once the electrics are in place I'll be finished in no time. However while I'm waiting for the electrics to be done, I can still get the three other walls finished.

One thing I also want to do at a later stage is add a seal around the roof. I noticed that the roof edging boards do have a very tiny gap, meaning water can trickle under them. It would never get into the shed as its on the overlap, however I've bought a bitumen sealant that is designed to fill gaps around fascias. I'll likely also add some extra sealant on the joins of the roof felt just to make me feel that bit happier about it being water tight.


  1. Hi - again a great read.

    Can i ask, is the air flow in the roof that important? having looked at various cabin kits with insulation in them none of them seem to consider that.

    Another thing is the wall lining membrane - is it likely that this is doing anything?

    Im not calling you paranoid or wrong :) i expect you know more than me its just something i have never considered. (and now have to)

    very interesting and certainly pause for thought.

    1. Hi Ross,

      Usually you wouldn't need much in the way of airflow, however because of the 'hybrid-warm' roof that I've had to go with, there is a possibility of condensation forming inside the room. If you've got a 'cold roof' you'll have to have the ventilation above the insulation so wouldn't need it in the actual room.

      The only real difference here is that the vent goes into the room's open space instead of above the insulation. It'll only have to be a very small vent to do the equivalent of putting a window on a latch I'd have thought.

      I did see on a number of forums where people didn't do any ventilation and a few months down the line found that their insulation and plasterboard had started to mold - better to be safe than sorry IMO!

      As for the wall membrane, its likely that it'll do bugger all, but I really just wanted it there on the off chance that water got through the walls. It probably is me being over paranoid about it :p I had to buy a roll of the stuff for the inside of the roof anyway so opted to go for a 50m reel and just do the lot. The cost difference was minimal - I actually found it a bit of a pain trying to get hold of a smaller amount of the stuff. I guess its normally used on large builds.

  2. Hi Ricky.

    ME again. Did you use the ultraperm stuff on the inside for the ceiling or the outside (on the roof) ? I was thinking of getting some but (and i could be wrong) it seemed more designed for outside use and then put felt/shingles on top of that?

  3. Ricky

    Excellent blog!

    I am in the process of having a cabin installed which is double skinned (2 x 28mm walls with 70mm Celotex insulation, with roof & floor insulation).

    I intend to use this as a garden office so wanted a high standard of interior finish (i.e. not just painted boards & electrical conduit running up the walls). So I plan to do exactly what you have done & plasterboard the walls & ceiling (by fixing to battens) and fit skirting board and engineered flooring (with electric underfloor heating). I planned to run the electrical cable in the void between the plasterboard and inner cabin wall.

    However, I mentioned this to the installers building my cabin and they advised that it wouldnt work as the expansion/contraction of the cabin walls would cause the plasterboard to flex/crack.

    I just wondered how, one year on, your garden office has suffered similar problems?

  4. Hi Steve,

    The walls in here are basically free standing. I left a 1.5 inch gap between the outer wall, and the stud walls to allow for a bit of flexing. The only part that is attached is the floor, the 'box' of the walls essentially supported itself once the frame was complete.

    I've not had any problems on the inside from expansion/contraction. Where I painted the outside a small 1inch gap of bare wood appeared around the door frame, so it did expand slightly, however the design of the doorframe allowed for movement around it.

    Overhall having been in here for about 10 months now it's been great. I was worried about things like the expansion, and the condensation however not had a single issue so far!

    The underfloor heating will certainly help - thats the only thing I regret not doing! The celotex helps massively, but I always found the floor a bit cold in the winter.

    For the electrics I had them brought up through a small hole drilled into the floor next to the stuf wall floor baton, the cable then runs up the outside wall into a power box with a flip-switch to kill all power to the plug sockets. From there it just runs to three double sockets. The socket boxes were simply attached to the side of the battons with supports built around them. Overall very stable and no chance of cables getting 'nipped' by any expansion that might occur.

    Good luck with your build - its well worth it! :)

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  6. Good blog. The walls are fixed to the ceiling and ceiling is fixed to the roof? But still no issues with contraction/expansion there?