Build a shed Mike's way

[yogibe4r]

Mike,
My intention was to rely on the joists to stop the walls spreading. What would be the maximum gap between 'un-joisted' rafters? The wife has already earmarked the 'loft space' for storage.

Regards, JK

edit: The wife has now informed me she is to be referred to as SWIMBO from now on!

 

[MikeG.]

JK,

in which case, we will simply double up the last of the rafters that have a tie, and use a structural ridge beam to span between them. The rafters without a tie will be "held up in the air" by the structural ridge beam, and thus prevented from spreading the walls.

What sort of roofing are you proposing (tiles, felt, sheet-roofing etc)? Are you required to get Building Regulations approval for this shed?

Mike

 

[yogibe4r]

Mike,
The roof will be 12mm OSB covered with felt shingles. Not sure about building regs, as neighbour built a simliar structure and told me he didn't need them. However will be popping down the planning office to make sure. Overall height is 3.85m.
Regards, JK

 

[MikeG.]

I'll sort your timber sizes out when I know whether that this doesn't need BR approval.

Mike

 

[yogibe4r]

After a brief conversation with the duty planning officer, they have explained that only the electrics may be of concern to them. This I will plan closer to build time.

Regards, JK

 

[yogibe4r]

Not sure if this thread is still being looked at due to recent events, but can anybody else have a look at my roof design to see if it's ok?

Sorry to be a noob without a clue!?!

 

[9fingers]

Not sure if this thread is still being looked at due to recent events, but can anybody else have a look at my roof design to see if it's ok?

Sorry to be a noob without a clue!?!

I can only offer a tiny fraction of Mike's expertise but post some details and we can have a look.
Bob

 

[yogibe4r]

Thanks 9fingers.

Proposed timbers are 6x2 for rafters and joists, 8x2 for ridge beam.
Roofing will be 12mm OSB and felf shingles. All rafters sit above wall studs, hence slightly odd spacing in the centre. The ridge beam isn't to be structural so my concern is whether the amount of space between 'un-joisted' rafters would cause the walls to spread.

Thanks in anticipation, JK

 

[9fingers]

Such a shame we don't have Mike here for an experienced opinion.

I share your concern on wall bulges. Very attractive to have what must be about a 3m access to the roof but unless you are going to store very long lengths up there, I'd be tempted to close is up to say 2m and make sure the wall plates on top of your studs lay with the widest dimension horizontal to stiffen the walls as much as possible.

Also I wonder if your joists are over spanned at 6x2. If it were my shop, all sorts of stuff would end up there imposing quite a load. I think I'm right in saying if that were a habitable floor you would be looking at least 9x2 to meet regs. So I'd consider 8x2 stress graded timber. Should not add a huge amount to the cost.
Are you going to put a deck up there? It would tie the joists together nicely.

The OSB will tie the rafters and stop them racking.

Thes are just my gut feel - I'm not a professional in this field.

hth

Bob

 

[yogibe4r]

Updated with 8x2 joists, extra joists, deck of 22mm chipboard, and doubled up last pairs of rafter.

Thanks for your advice 9fingers

Cheers, JK

 

[9fingers]

That looks better to me. Possibly no real need to double up on the rafters though?

Bob

 

[bucephalus]

Many thanks for this useful information - came in very handy when planning my workshop.

 

[9fingers]

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

 

[bucephalus]

Oh, right - I didn't know. I am continually humbled by how helpful everyone is here. Many thanks.

 

[9fingers]

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

 

[Andy RV]

Bump for a very useful thread!

 

[Wizard9999]

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.

 

[Zeddedhed]

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

 

[Deejay]

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

 

[Wizard9999]

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