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By ChrisxBates
#937863
I am considering constructing a workshop based on Mike’s drawings on page 1.

Thanks to Mike and all others that have contributed. An excellent, informative thread.

My question is regarding the mineral wool insulation in the walls. This comes in two forms the denser cavity wall type batts and the lighter loft type insulation.

Firstly…. Which type are people using?

For the insulation to be effective there mustn’t be an air gap between the mineral wool and the OSB. If there were an air gap, this would allow the cold external air to come into contact with the OSB making the insulation ineffective.

Second….. How do we ensure the insulation stays in place and doesn’t fall away from the OSB overtime? Hence causing an air gap and making the insulation ineffective.

Previously when I have used mineral wool, it has either been held in place by gravity or sandwiched between two surfaces.

I would be interested in hearing your views.
By Wizard9999
#938885
ChrisxBates wrote:I am considering constructing a workshop based on Mike’s drawings on page 1.

Thanks to Mike and all others that have contributed. An excellent, informative thread.

My question is regarding the mineral wool insulation in the walls. This comes in two forms the denser cavity wall type batts and the lighter loft type insulation.

Firstly…. Which type are people using?


All in the name isn't it, the cavity wall batts are designed for that job and so have the rigidity needed. Mike did a very long thread on his recent workshop build on TheWoodHaven2 and if you searc for it you will see that is exactly what he used.

Terry.
By SlayWitch
#949740
Thanks for posting this, super helpful as I am considering to start on a similar project so it is good to see what kind of approach other people are taking. How is everything going?
User avatar
By Deejay
#949782
SlayWitch wrote:Thanks for posting this, super helpful as I am considering to start on a similar project so it is good to see what kind of approach other people are taking. How is everything going?


Mike doesn't post here any longer.

He contributes over on The Woodhaven2.

Cheers

Dave
By technium
#1069366
Thanks for this Mike, If I decide to build mine myself then I will try and use this for mine. thanks

Colin
By Myfordman
#1173090
MikeG. wrote:I've put it off long enough!

Hopefully, this will save me hours of repetition:

Note that this only applies if your building does not require Building Regulations approval. If it needs to meet the regs, the base will need to be properly designed according to the local soil conditions and tree locations etc.

Image
The concrete should be laid on:
-clean compacted hardcore, say 100 to 150 thick
- sand blinding (for the protection of the DPM)
-1200 gauge DPM

Note the golden rule of walls: The Vapour Barrier goes on the warm side of the insulation!!!!. The vapour barrier in this drawing is the OSB, which is full of glue and therefore highly resistant to the passage of moisture.

Key features of this design are the brick plinth and the 25mm air gap between the frame and the back of the cladding. In the roof, it is essential that there is a 50mm clear ventilated void above the insulation, and that there is a continuous 25mm gap at the eaves (with insect mesh) to provide air movement. These features are essential to prolong the life of the building, and to keep everything inside dry.

You can omit the floating floor if you wish. My own workshop simply has the concrete slab as the floor.

I imply no structural calculations for the roof! Each roof should be designed individually, and I am always happy to help with that. I would suggest min. 150mm rafters so that you can fit 100mm of insulation in without restricting the airflow, but with some roofs the rafters will need to be much deeper for structural reasons.

The boarding can easily be replaced with render, so long as the airflow behind is maintained, and this is made easier by using a backing of building paper behind the EML (mesh) so that the render doesn't get pushed through too far into the cavity. Note that with boarding there should only be one nail per board per stud position, and that that nail should be situated about 30mm up from the bottom edge of the board.

And now a variation: with Timber Suspended Floor

Image

I like this less, particularly because of the large step up and the resulting taller building (or reduced headroom). This isn't the only way to do this, but the principle is to have the insulation hard up under the flooring, with a continuous ventilated void below the joist.

The surface of the reduced ground level below the floor should either have a geotextile membrane or a layer of lime laid on it, or it should be treated with a weed-killer. Avoid using this design in wet/ boggy areas because of the reduced ground level below the floor.

I hope this helps.

Mike


I've edited the original post to make the vital diagrams visible and make sense of the text.
Bob
By Hornbeam
#1178323
There is no reason why insulation quilt cannot be used in walls (most large warehouses use quilt for built up cladding). What you need to do is prevent it from slumping down in the cavity creating voids. One way to stop this is to use stick pins which are long metal pins with an adhesive base. The pins are about 2/3rds of teh cavity depth so dont cause cold bridging. Glass wool is much easier to use than stone wool as fibre length is much longer and so it is less likely to break. I would use a quilt thickness at least 10mm thicker than your cavity and ensure it is fully lofted to fully fill the cavity. Quilt insulation has a slightly lower thermal conductivity than denser batts and willl be easier to fill the cavity , PIR foams insulation has much better insulation than MW so you only need about 60% of the thickness for the same U value. I would not recommend polystyrene due to the fire risk issues

Ian
By dom68
#1221676
hi mike if i go with the timber floor design how many courses high can the plinth be if i keep it a single bricks width?

thanks, dom.
By dom68
#1221681
also would be acceptable if i didnt bring the osb down to the floor? ie could i use one sheet of 8x4 horizontally on the back of my frame then place the frame on top of plinth and fasten down with straps the same as in your diagram?

thanks.
User avatar
By MikeG.
#1221684
The bottom of the sole plate/ DPC should be at least 2 courses above ground level. Three is better.

That would be fine with the OSB. The one thing against that is that the panels become very heavy, and the slightest gust of wind at the wrong time can make life very tricky. However, if you've got sufficient help, then yes, that's no problem.
By dom68
#1221709
great.. so if i build a 8/9 course single skin wall/plinth for the frame to sit on all should be ok?

my thoughts at this stage are for my 8x6ft shed. im thinking my wall height to be around 2m. the top 1220mm framed and the lower 800mm single skin brick. all approx at the mo..

im also thinking of using new treated scaffold board ripped to 38x50mm to build the framed sections.. retreated after cutting.. does this sound plausible?

dom.
User avatar
By MikeG.
#1221715
Hmmm. That's quite tall for a half-brick wall. It could look rather odd, too. That brickwork could be a bit vulnerable around the door opening (and 800 is 10 or 11 courses). You might be OK if you do piers either side of the door which are 215 deep.

50x38 framing would be just about OK for a really small shed, say 6'x4', but it isn't enough for a proper building. 50x50 would be my absolute minimum for any thing bigger than 6'x4', but 75x50 is really the least you'd expect to use for anything you'd work in.