Workshop Design

[Deejay]

Evening Paul

The fire risk is often seen when screwed connections are not correctly mad, often by DIYers.

Shurely shome mistake

Cheers

Dave

 

[NetBlindPaul]

What mishtakkee?.... :lol:

 

[Dibs-h]

The fire risk is often seen when screwed connections are not correctly made, often by DIYers.

I understand where you are coming from - but most folk who self-build workshop, are way beyond the realm of DIYers and almost in the realm of some Pro's. In some cases, the work of Pro's isn't upto the same level. Some admittedly not all.

The potentially lethal fault can come from several failure modes, to do a full FMEA I would need the full details of the install, the upstream cct protection and the characteristics of the supply at the origin.

My own preference would be to bring the supply inthru a conduit into the slab, ensuring min bend radii are not exceeded. But obviously there is more than one way to skin a cat. A full FMEA analysis would be way overkill in this type of sceanrio - i.e. bring the cable up outside into an enclosure. But we can agree to disagree.

Please also remember that when an electrician comes to work at your home, this becomes his pace of work he thus has to comply with all work place legislation.
If he is to fit this for the constructor he has to also comply with CDM & work at height legislation, thus the joint must be in a position where by it can be inspected without the necessity of working at height as it is possible that live working could be needed at that location.
Thus remove the joint and you remove the requirement for access for inspection & testing at height.

Paul

Yes I agree. Working at height regs are there for a reason and it is encumbent on the contractor to carry out an assessment. But even in this scenario - no contractor is going to specify full scaffolding. I certainly feel that live working in the scanario mentioned is highly unlikely.

Yes remove the joint & you remove a few requirements but as with all things construction it's a trade-off. In this case the OP doesn't want to bring the cable up thru the slab - I would, but he doesn't. Again a cable being brought up outside into an enclosure, might not be the best method, but I don't feel it's an invalid method and that i feel is getting missed here. There is best practice and there's worst practice (i.e. illegal) but some things do fall inbetween, i.e. acceptable.

On the subject of connectors - ever seen a torque spec for tightening torque that should be used on screw down connectors? I doubt they're supplied much these days or even exist, except for the true industrial connectors.

Dibs

 

[NetBlindPaul]

Dibs,
It would be my preference to bring the cable through a duct in the floor slab also, however, there is nothing wrong with bringing the cable up the exterior of the building and then as i said entering through the soffit area.
An FMEA should be done as a routine part of any design exercise. It is the extent of the FMEA that should be limited.
We will have to agree to disagree on jointing a cable in an exterior enclosure when it is unnecessary then, which it is.
There is no reason for full scaffold, especially if you are not jointing the cable in an external enclosure.
Just because the cable does not come up through the slab does not mean it has to be jointed in an exterior enclosure.
Yes I have seen many torque specs even today for screwed connectors of a professional grade.

Please as I have already said, you will need to answer to your insurer, the LABC & others perhaps should an issue arise.

 

[Deejay]

Morning KC

Mike - I am trying to stick to wood so I hope 200 x 500 x c.7000 for my ridge.

Sounds a bit big. Are you sure?

200 x 50 sounds better to me.

Cheers

Dave

 

[Dibs-h]

Morning KC

Mike - I am trying to stick to wood so I hope 200 x 500 x c.7000 for my ridge.

Sounds a bit big. Are you sure?

200 x 50 sounds better to me.

Cheers

Dave

Yeah does sound big. When I said "bigger the better" I meant the workshop, not the ridge. :wink:

 

[chipchaser]

Hello Kingcod,,

The preferred method for bringing a supply cable into a building is via a duct rising through the floor. The duct could be a clay or pvc pipe eg a drain pipe because that would be easy for you to source. Some electricity boards use a black pvc duct. From memory your cable should be 450mm below ground level with mechanical protection, cast concrete tiles are often used if it isn’t in a duct, and warning tape above.

At the building you need a gentle bend which will rise through the floor. If you have a plastic DPM carefully cut a star shape at the point where the pipe comes through and seal the turned up plastic with tape wrapped around the pipe. Builder’s merchants will have the right tape. You may already have bought some to seal laps in the DPM if you have a large floor.

You need to site the intake carefully so the cable rises in a suitable spot, easily and safely accessible for maintenance because ideally your distribution board will sit on the wall directly above the intake at a safe and convenient height. Avoid obvious poor locations like behind the inward opening door to your shed because you don’t want to be giving your leccy the kiss of life after pushing him into the live board he has just connected for you and so on. There should be a safe open area around the board in the finished building.

IIRC bringing the cable into a wall cavity is not acceptable, it certainly isn’t sensible, just awkward. Likewise it is just plain sensible to avoid unnecessary joints especially below ground.

Tha cable feeding your shed should be fitted with the appropriate protective device (RCD or RCBO) at the source (your consumer unit or a sub DB added for the purpose). There should also be a double pole isolator at the source as it should never be necessary to work live on circuits within your property.

HTH
Graham

 

[NetBlindPaul]

Couple of follow up points.

A cable installed in accordance with BS7671 no longer has a defined depth at which to be buried, it is up to the competent person installing the cable to ensure it is buried at a depth sufficient to prevent damage occurring.

You can bring cables in through cavities and run them through cavities as long as you can comply with all of the raft of legislation and guidance that is required to do this.

Underground cable must incorporate earthed mechanical protection, however it is not statutory to have additional mechanical protection such as tiles, however this is a blinking good idea!
The warning tape is required

It is not necessary to have a residual current device at the origin of the sub main circuit depending on the installation conditions and circuit design details.
In fact there is guidance to say that you should not install such protection there for certain types of installation.

It is illegal to work as part of a business undertaking on live circuits except in the situation where it is not possible to work with the circuit isolated.

Live working must only be undertaken by persons competent to do so with the necessary precautions in place.

There are requirements in legislation for clear space around DB’s.


With a new build and design there need not be such compromises, as these will be merely financial. Financial compromises where safety is concerned are a very grey area.
Please remember, even though you may be DIY and may be not running a business you still must comply with the building regulations, and really you must comply with CDM regulations if you delve into the detail. The reason being is that the premise may well be sold on in the future.

The building regulations require absolute compliance and they can be applied such that any non compliant works must be re-done in compliance, this remember includes the requirement to insulate structures, include natural lighting etc. no matter what the intended purpose / “person” constructing. LABC have within their powers to have the construction “removed”!

OK as far as the wording, goes the “Building Regulations” Regulation 7 requires that any building work which is subject to the requirements imposed by Schedule 1 of said regulations should be carried out with proper materials in a workmanlike manner.
If you are running a business undertaking from the premises concerned, then on top of LABC, you will have wither LAEH or HSE FOD to answer to should it be found that the installation does not meet the requirements of “accepted” practice. Which in such a situation as this would be how the sub main supply circuit would have been designed & installed by a specialist in the field. i.e. an electrician/electrical engineer.
If you are a hobby user working at home then should something go wrong then you will have to fight your insurance company to get the payout if they “smell a rat”.
They will spend considerable sums of money to avoid the payout if it is commercially viable to do so.
IF you check the small print of your house insurance policy, you may well be unpleasantly surprised!

As I was asked to back up my comments earlier with regard to the electrical installation then IF you want a BS7671 Reg. No. as to why you should not fit an external joint box to go from SWA to T&E in your sub main, try 132.7, 133.3, 134.1, 510.1, 510.2, 512.2, 513.1, 521.1, 522 (group), 526.1, 543 (some of this group),.
You would also need to refer to reg 422.3 when undertaking your internal install.

As I say business premises, EAWR89, PUWER98, MHSWR, building regs & your insurer, hobby premises building regs & your insurer will call the shots even if you don’t realise it.

 

[Dibs-h]

The building regulations require absolute compliance and they can be applied such that any non compliant works must be re-done in compliance, this remember includes the requirement to insulate structures, include natural lighting etc. no matter what the intended purpose / “person” constructing. LABC have within their powers to have the construction “removed”!

That's the theory - the practice is something else. That isn't a feeling - that's been borne out from experience. Most folk with the above impression\belief are rather shocked when the reality surfaces.

 

[NetBlindPaul]

Dibs, I have seen the reality also, however that is the statute law, one should not advocate breaking the law should one!

 

[kingcod]

So I have my concrete base in place now (pics to follow) and need to order up my concrete blocks. I am getting conflicting advice.

My design has a couple of rows of 440x215x100 standard blocks topped with a timber frame and timber roof. I am hoping to use the lightest blocks possible as I have to barrow them such a distance to the site. A builders yard is saying I need 7n dense blocks but surely I can get away with aerated blocks of the 3.6n variety? the blocks are above ground and are load bearing.

- oh and would hollow blocks do? I am thinking of using these to inset anchor bolts in for the sole plates. A bit like yer man here is doing:

 

[Dibs-h]

Dibs, I have seen the reality also, however that is the statute law, one should not advocate breaking the law should one!

Not in the slightest - I was referring to the rubbish that local BR departments of Councils will and do pass. Not the slight's of hand the builders\clients will pull.

So I have my concrete base in place now (pics to follow) and need to order up my concrete blocks. I am getting conflicting advice.

My design has a couple of rows of 440x215x100 standard blocks topped with a timber frame and timber roof. I am hoping to use the lightest blocks possible as I have to barrow them such a distance to the site. A builders yard is saying I need 7n dense blocks but surely I can get away with aerated blocks of the 3.6n variety? the blocks are above ground and are load bearing.

- oh and would hollow blocks do? I am thinking of using these to inset anchor bolts in for the sole plates. A bit like yer man here is doing:

You would need to talk to a structural engineer as to what the compressive strength needs to be for your plinth. No different in my mind to the plinths that are used in masonry construction, i.e. the 1st few rows on a brick house will have engineering bricks and then normal bricks.

I personally don't think 3.6N blocks would be sufficient, as it's not just the static load they have to bear up to, but also the dynamic loads due to wind, snow, etc that are transmitted thru to the foundations.

In the absence of paying for an engineer - I'd play safe and use the 7N blocks.

As for lugging blocks - I had mine delivered round the front, moved them 1 at a time, down a 3 car length drive, past a single garage, down 5 steps and finally 3m's down the garden and onto the site. And that was 9 full packs. So I think you've got it easy, with less blocks and a barrow! :lol:

HIH

Dibs

 

[kingcod]

The 7N blocks are all set to go. An hours work with a barrow to get on site . I am now puzzling over the position of the DPC and the sole plate. If I am resting the sole plate directly over the DPC can I still fix anchor bolts / paslode shots through the DPC into the concrete blocks? Surely thats another compromise on the DPC layer? I can't seem to find a simple alternative. I am looking at straps to fix the sole plate but not sure where to fix them at the base. If only I had followed the full Mike Garnham technique and concreted straps into the base. *sigh*

Would a DPC between the first and second course of concrete blocks do any good? Or would that make mortaring up the blocks a bit difficult?

 

[Dibs-h]

The 7N blocks are all set to go. An hours work with a barrow to get on site . I am now puzzling over the position of the DPC and the sole plate. If I am resting the sole plate directly over the DPC can I still fix anchor bolts / paslode shots through the DPC into the concrete blocks? Surely thats another compromise on the DPC layer? I can't seem to find a simple alternative. I am looking at straps to fix the sole plate but not sure where to fix them at the base. If only I had followed the full Mike Garnham technique and concreted straps into the base. *sigh*

Would a DPC between the first and second course of concrete blocks do any good? Or would that make mortaring up the blocks a bit difficult?

I don't see why you couldn't set anchor studs into the blockwork and then lay the DPC on top, with holes for the studs to poke thru, then use washers and nuts to hold the soleplate down. You could always seal around the studs with a construction sealant if you have any concerns regarding compromise.

I would put the DPC under the soleplate.

HIH

Dibs

 

[johnf]

The dpc should be on below the first course of concrete blocks directly on the slab which should be 150mm above the external ground level
You can then build fixing bolts into the vertical joints or just plug and screw the sole plate directly to the blockwork
ps 4/1 mix for the mortar

 

[kingcod]

So a bit more progress to report on.


Site ready for concrete: shuttering, DPM, steel mesh supported to 'float' inside the concrete pad.


A gut busting day of barrowing lots of concrete

It takes 5 of us about 2 and a half hours. The guys from the concrete truck can't quite believe the 100 metre hill between the road and the site. Extra beers for their efforts.


The wonderful numpty proof 'Bricky' makes the blockwork easy


Blockwork all done with a DPC sitting between the two tiers of blockwork.

I have a few questions but will post them when I have my thoughts together.

oh- the sole plate I reckon will just be fastened directly into the blockwork with masonry fixings.

 

[johnf]

So what stops the damp rising into the bottom course of blockwork
PS I am a bricklayer of 45 years experiance

 

[Dibs-h]

So what stops the damp rising into the bottom course of blockwork
PS I am a bricklayer of 45 years experiance

If there hadn't been a DPM under the concrete I would have thought nothing, but looking at the earlier pictures - there's a DPM under the concrete, in which case a DPC appears pointless.

Dibs

 

[kingcod]

So what stops the damp rising into the bottom course of blockwork
PS I am a bricklayer of 45 years experiance

If there hadn't been a DPM under the concrete I would have thought nothing, but looking at the earlier pictures - there's a DPM under the concrete, in which case a DPC appears pointless.

Dibs

Yes there is a1200 guage DPM under the concrete. As for the DPC ... I was just following Mike Garnham's design which shows both:

build-a-shed-mike-s-way-t39389.html


Which brings me to a few questions:

1. Double sole plate or single sole plate? I have seen designs with both.
2. How to treat the DPC at the doorway. If you can imagine it appears out the wall at i block height ... should I extend it down and around the base of the door frame and door step (which will all be in wood)?
3. Any special treatment needed for the wood fram, particularly the sole plate as the most potentially exposed section? Do I need tanalised timber or will Kiln Dried C16 do?
4. screws with an impact driver or ringnails with an air nailer to stick build the frame?
5. Should I fastidiously protect the half built frame from the weather or just work on and let it dry through once it gets clad?

Thats it. Advice greatly appreciated

 

[Dibs-h]

So what stops the damp rising into the bottom course of blockwork
PS I am a bricklayer of 45 years experiance

If there hadn't been a DPM under the concrete I would have thought nothing, but looking at the earlier pictures - there's a DPM under the concrete, in which case a DPC appears pointless.

Dibs

Yes there is a1200 guage DPM under the concrete. As for the DPC ... I was just following Mike Garnham's design which shows both:

build-a-shed-mike-s-way-t39389.html


Which brings me to a few questions:

1. Double sole plate or single sole plate? I have seen designs with both.
2. How to treat the DPC at the doorway. If you can imagine it appears out the wall at i block height ... should I extend it down and around the base of the door frame and door step (which will all be in wood)?
3. Any special treatment needed for the wood fram, particularly the sole plate as the most potentially exposed section? Do I need tanalised timber or will Kiln Dried C16 do?
4. screws with an impact driver or ringnails with an air nailer to stick build the frame?
5. Should I fastidiously protect the half built frame from the weather or just work on and let it dry through once it gets clad?

Thats it. Advice greatly appreciated

1. A single wall plate should do. I don't see the advantage in a double one.
2. yes extend it down and under the door frame\step.
3. I've used normal timber, but mine was behind a block wall. If exposed, might be safer to go with a treated one. You cpuld always use DPC under it and then wrap it round over the top, from the outside of you wanted. I'd be inclined to use normal timber. Then frame wrap it and make the counter battens go below the sole plate and fix the ends into the 1st course of blocks. That way your cladding (fixed to the counter battens) extends below the sole plate and you shouldn't have any issues with moisture.
4. Screws and impact driver are definitely the way to go, especially of you need to make adjustments. DAMHIK!
5. Protect it as best you can, but no need to go OTT. Dry it out once wrapped in building\frame wrap.

HIH

Dibs