Build a shed Mike's way

[Deejay]

Morning all

Mike Garnham is posting the construction of his new workshop over on WH2

http://www.thewoodhaven2.co.uk/viewtopi ... 1538#p1538

Cheers

Dave

 

[johnny]

thats an excellent guide Mike and very imformative ...although a bit over the top for a garden shed imo It makes my shed look like a 3rd World shack lol. I guess what we are really talking about here is more a workshop than a shed to store the lawnmower .


The only suggestion that I would make is regarding the detailing around the sub structure brickwork to internal floor juncture. The manner in which the Dpc is sealed to the Dpm to prevent water ingress is so often left unclear or unresolved and is arguably the most critical juncture in any building.
Rain spatters up to a height of 6-8 inches so the bottom two courses of brickwork are going to be constantly wet during spells of heavy or prolonged rain ,Any tear or untaped gap to the Dpc or Dpm around the edge of the chipboard flooring is going to allow the edge of the chipboard to get wet and rot.
My suggestion would be to show the Dpm folded up at the edges and overlapped with, and taped to, the Dpc which should be carried down over the internal edge of the sole plate so that everything below the sole plate is completely sealed like a boat. All joints in both the Dpm and Dpc should be lapped and taped otherwise any significant ground pressure will allow water ingress.

Just a reminder that to be 'Permitted Development' and be exempt from Planning, any garden structure needs to be a maximum of 2.5mts high unless a minimum of 2mts from any boundary.

 

[Wizard9999]

Johnny

If you are interested follow link in post above yours. mike's new build progressing well. He has now explained dpm question. In short, if you concrete plinth is above ground folding up the dpm around would cause it to be damaged by exposure to UV, but if plinth level with ground that is also what he suggests, but folding under brick plinth, not taking up to level of EPC on top of dwarf erick wall.

Wizard9999

 

[Harbo]

Mike doesn't post on here and he is a very experienced Architect.
You will have to follow it on Woodhaven2

Rod

 

[johnny]

Johnny

If you are interested follow link in post above yours. mike's new build progressing well. He has now explained dpm question. In short, if you concrete plinth is above ground folding up the dpm around would cause it to be damaged by exposure to UV, but if plinth level with ground that is also what he suggests, but folding under brick plinth, not taking up to level of EPC on top of dwarf erick wall.

Wizard9999

Thanks Wizard I have been following Mike's new shed build with interest as I am currently constructing one of my own allbeit on a somewhat smaller scale

The waterproof detailing shown in Mikes drawing isn't very clear as shown in the first image. It would probably be clearer if that section was blown up a bit.

I was not so concerned with rising damp tracking through the concrete to the substructure brickwork as the damp ingress through the brickwork into the edge of the flooring .
The juncture between the foundations/sub structure of a building and the DPC must be sealed by lapping and taping to protect the structure and internal finishes. There must be no area unsealed .

The reason why you see so many new buildings with the DPM left stuck up in the air ,hacked off and blowing in the breeze is because builders have no understanding of how to tie the DPC's to the DPM so they just hack it off flush with the screed leaving the most critical area of a building unprotected.

Rain splashing up the brickwork will penetrate the brickwork and soak the edge of the flooring in the first construction detail as shown. I think I would prefer to see the restraints on the outside of the brickwork bolted to the edge of the slab on view. That way the condition of the straps is constantly on show and can be monitored and the straps don't interfere with lapping and taping the DPM to the DPC

 

[ChrisxBates]

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.

 

[Wizard9999]

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.

 

[SlayWitch]

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?

 

[Deejay]

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

 

[SlayWitch]

Ah apologies, I didn't realise :S I will check if there has been updates then. Cheers Dave!

 

[technium]

Thanks for this Mike, If I decide to build mine myself then I will try and use this for mine. thanks

Colin

 

[Muzza80]

Very helpful post, thanks!

 

[Myfordman]

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.

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

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

 

[Hornbeam]

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

 

[dom68]

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.

 

[dom68]

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.

 

[MikeG.]

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.

 

[dom68]

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.

 

[MikeG.]

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.

 

[dom68]

how about 8 courses of bricks with piers by the door and 75x38? or is 38 just too thin? sorry to be a pest :roll: