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By 9fingers
#468206
That looks better to me. Possibly no real need to double up on the rafters though?

Bob
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By bucephalus
#518511
Many thanks for this useful information - came in very handy when planning my workshop.
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By 9fingers
#518514
bucephalus wrote:Many thanks for this useful information - came in very handy when planning my workshop.


If you ever need to get hold of MikeG, he no longer frequents this forum but can be found via The Wood Haven.

Bob
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By bucephalus
#518569
Oh, right - I didn't know. I am continually humbled by how helpful everyone is here. Many thanks.
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By 9fingers
#518586
bucephalus wrote:Oh, right - I didn't know. I am continually humbled by how helpful everyone is here. Many thanks.


Ah! we do have a plan though :twisted:

One day we will come asking for help from you in return!! :lol:

Happy shavings


Bob
By Wizard9999
#898531
I am in the process of planning my first workshop build. Have been researching on the 'net and this post appears to provide the definitive construction detail. As a complete non-builder type I have one question relating to the initial (extremely helpful post). How do you go about fixing the sole plate to the dwarf wall used to keep the timber off the ground? If I simply plug and screw it won't I screw straight through the DPM / DPC? If I do just screw through them is the impact so small as to not worry about it?

Many thanks in advance for any answers, advice, help...,
Wizard9999.
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By Zeddedhed
#898538
You're right Wizard, screwing down the sole plate does technically compromise the DPM but as you state it's not significant enough to worry about it.
I build quite a few timber frame buildings, both habitable (houses) and non-habitable (Workshops, pool houses etc) and go for a belt n braces option - drill your hole, squirt in some frame sealant, bang in a decent size frame fixing (Fischer or similar) and when you tighten it up the sealant will effectively remake the continuous DPM.
HTH
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By Deejay
#898546
Afternoon Wiz

How do you go about fixing the sole plate to the dwarf wall used to keep the timber off the ground?

If you look carefully at the drawings, they show galvanised straps bent over the top of the sole plate.

Cheers

Dave
By Wizard9999
#899135
Ah, OK Dave, now I get it. The sole plate itself is not fixed to the dwarf wall, but the metal brackets are screwed down onto the dwaft wall - hence the comment through the thread about stopping the shed blowing off the dwarf wall in a big storm. So there is no piercing of the DPC.

Having read your post I did go back and study the original diagram again and I have a couple of further question that I hope somebody can help with.

1. The diagram shows a layer of 500 gauge polythene between the concrete floor and the insulation under the floating floor which then seems to lap up the dwarf wall to the height of the floating floor. This must be running on the inside of the metal bracket, i.e. not between the bracket and the dwarf wall (unless a hole is cut in the polythene for the bracket to poke through) so can't lap over or under the DPC running along the top of the dwarf wall. The floating floor is about the same height as the top of the first brick of the dwarf wall. So, in this structure what prevents damp coming through the the dwarf wall and into the inside skin of the shed (in the diagram this is shown as 11mm OSB)? Or am I now getting too paranoid about damp penetration now?

2. The 1200 gauge polythene under the concrete base seems to just stop at the edge of the base. Am I understanding this correctly, or when I put this down do I need to leave enough to lap up the side of the concrete base to stop damp coming into the side of the concrete where it is in contact with the surrounding soil? But then, if I do lap it up, am I creating a pool which if water ever does get into it will never have anyway of escaping, which I guess may be a reason for not lapping it up?

I'm sure my questions reveal I am a compete novice at this and I apologies if my questions revela utter stupidity, but I really want to understand what I am doing before I think about starting building my workshop. Any help would be much appreciated.

Wizard9999
By johnny
#902370
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.
By Wizard9999
#903012
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
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By Harbo
#903035
Mike doesn't post on here and he is a very experienced Architect.
You will have to follow it on Woodhaven2

Rod
By johnny
#903039
Wizard9999 wrote: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