Insulating and powering a new shed.

[TEAMYAKIMA]

I have just had a new shed delivered and set up.

 

I was quoted a very large sum by the shed manufacturer to insulate, line and power it.

 

I want to hide the electrics in the frame - ie no conduit running along the walls.

 

I want to insulate it and line it with 'nice' lining - nothing too cheap but not oak panelling!

 

With my last shed I insulated it with big thick sheets of  blue insulating foam bought from B&Q or similar. Someone told me that these days you 'spray' insulation foam - Is that appropriate?

 

I assume I put the electricity in first and insulate after that.

 

So here is my shed , how can I do what I want without bankrupting myself?

 

 

[Guius]

Nice shed, electrics are first and you'll have to drill the framing  to take the cables, I would do this a approx. eves height . Then I would photograph the cable run to make sure that when fixing the lining boards you don't accidentally go through a cable.

Regarding lining I've used Stirling Board before, it's not too costly, cuts easily and looks tidy. 

Have you got a main (supply) cable down to the end of the garden btw? To comply with Regs you'll need to put in a local consumer unit (2 way Garage Unit will suffice) 

And please remember - 'A shed is for life not just for Christmas'

Best of luck

 

Guy

[TEAMYAKIMA]

11 minutes ago, Guius said:

Nice shed, electrics are first and you'll have to drill the framing  to take the cables, I would do this a approx. eves height . Then I would photograph the cable run to make sure that when fixing the lining boards you don't accidentally go through a cable.

Regarding lining I've used Stirling Board before, it's not too costly, cuts easily and looks tidy. 

Guy

 

Hello Guy

 

Thanks for your input. What about insulation?  What do you know about this spray insulation I've heard about? I understand a professional comes and does it ….. know anything about this?

 

Thanks again for your interest in my problem.

 

Paul

[Damo666]

If the 230v electrical cables are encapsulated within the insulation then you will need to increase the cable size, as electrical resistance increases with the insulation and the cables could overheat and start a fire. A qualified electrician can advise you on suitable cable sizes, but ordinary twin & earth won't do if surrounded in insulation. Alternative is to de-rate the cables. See here top chart. This site also refers.

[34theletterbetweenB&D]

15 hours ago, TEAMYAKIMA said:

...Someone told me that these days you 'spray' insulation foam - Is that appropriate?...

Certainly has advantages in speed and efficiency of sealing. I cannot make a direct recommendation from experience but a friend who is a retired civil engineer is very happy with the work done in a similar wooden structure (a 'studio/garden room' already at the property he purchased) by a business trading as 'Thermofoam'. He felt they were properly able to advise on the appropriate foam type for fire retardation, and were right on top of avoiding insulating the electrical wiring.

 

Neat shed, you might want to fit some guttering though!

[chris p bacon]

I've looked at sprayfoam before for various projects but found the cost is almost double for no extra benefit.   I'd fit a minimum of 50mm Celotex to the wall and leave an air gap between it, and the outside boards, the joints need to be taped with foil tape and this will create a vapour barrier. You will probably have to fix an extra batten to the uprights to achieve this. 

 

The ideal is to fit 50-65mm between the uprights then 25mm continuously over the top, you can fix through the 25mm into the uprights or fix a counter batten over. I would increase either board for the ceiling.

Don't forget the rear of the door, simply  hanging a heavy curtain pulled across when leaving can work to reduce cold bridging.

 

Is there any particular reason why you want to conceal the electrics apart from aesthetic ?  Apart from lighting power is only usually required in 2 places (control panel and bench) so I would run it at eaves in trunking

[Western Star]

Shed looks like a sturdy and well made "pre-fab" structure - where from please.

[peterl]

If you are running the electricity from the house you should use 'armoured cable' for the supply to the shed. Should really be buried preferably in conduit. Best to check with your local authority as some have very specific requirements when providing electrical power to outside buildings.

Peter

[TEAMYAKIMA]

On 06/02/2019 at 09:28, Western Star said:

Shed looks like a sturdy and well made "pre-fab" structure - where from please.

 

They are not cheap but excellent quality - I had one in the garden of my last house and have only moved house so that I could get a bigger shed!

 

Google : CRANE GARDEN BUILDINGS

[Dick Turpin]

Looks like a very decent shed, you should be able to build the layout of a lifetime in that. One point though - what with the high wind we are having lately, consider going overkill with felt nails on the roofing material. On our summer house roof we have had large sections of felt ripped right off in high wind twice, and so the last time I repaired it I edged all the joints with tacks one inch apart. Been fine since!

 

Someone also told me to stick the felt on with tar, but I didn't do that. However, I still hate to hear the noise of gale force wind and imagine what I am going to find in the morning. Luckily it has been nothing more than the contents of neighbours' recycling boxes.

[chris p bacon]

2 hours ago, Dick Turpin said:

 On our summer house roof we have had large sections of felt ripped right off in high wind twice, and so the last time I repaired it I edged all the joints with tacks one inch apart. Been fine since!

 

Someone also told me to stick the felt on with tar, but I didn't do that. 

 

I wouldn't use felt that needed tack nailing as you've punctured the waterproof barrier. I would use 'Torch on' felt instead, you can hire a burner for about £20 (should only take a morning) and the felt will give you at least 10 years (I had a shed with it on which lasted for 15 with no visible signs of failure)

[big jim]

I insulated my shed with 25mm thick kingspan insulation between the uprights with a slight air gap behind them, over that I then put plywood ‘walls’ over the top 

 

electrically i I had a supply fed through one wall to a pair of sockets off which I ran LED lights via a 240 plug 

 

the whole thing js now defunct anyway as I’ve moved into the garage with the layout 

[Andymsa]

A nice looking shed, but oh dear there will be so many issues here. I'm sorry if I sound negitive but having built my own from scratch and it has a building control certificate gives a bit of an insite. 

 

Firstly dont run run your cables in the framework, looking at the size of the framework drilling holes it it will weaken it. As to insulation I would go celotex as you can't get the depth in the framework with the rock wall types. I would avoid the spray one, and don't forget insulate the floor. Use something called jab lite which is basically polystyrene and lay moisture resistant chipboard flooring on it. Don't forget a vapour barrier. Lining, don't use anything with wood strips, as you will get shrinkage go for sheet materials, IE plasterboard or 9/12 MM facing ply, the other issue is the ceiling I'm taking it that you see the underside of the roof. But without knowing how the arrangement of the supports here it is hard to offer advice here. As been said you will require a consumer unit in the shed and use armoured cable buried if possible. And exterior rated network cable if wanted would be a good idea if any computer control is used, unless your wifi reaches the shed. The door is a bit of a weak point I would think of extra security here to stop the little scrotes. Maybe an outside light is a thought. How will the layout be supported if with legs the legs will need to go over the floor supports as mid span between supports you run the risk of drop. Unless the floor is directly layed onto concrete not such an issue but if the floor is layed onto concrete is there a damp proof of some sort. I would look at guttering aswell as you will get a lot of water off that roof and will flood around the shed possibly during heavy downpours. I leave it there as i been negative enough but I'm just trying to be constructive.

Edited February 13, 2019 by Andymsa
Additional info

[Darwinian]

I have used ecohome insulation in my shed. Much cheaper than cellotex and easier to put up. It seems to do a decent job, certainly kept the shed cooler in the summer but I’ve not had time to see how it fares with me in there in the winter. Not quite finished the lining or insualated the door yet.

[Ian Morgan]

I wired my shed up myself, but got an electrician to inspect it, and do the final connection to the supply, and give me a certificate for if I sell the house.

 

I fitted a 'garage' consumer unit in the shed with two breakers, one for power and one for lighting. Plastic trunking runs all round the shed at waist height with 10 double sockets, wired as a ring main. (If red/black cable is used, a sticker must be displayed warning that it is not blue/brown)

 

Steel wire armoured (SWA) cable runs from the shed to an existing exterior socket which had its own breaker and RCD on the main consumer unit in the house. The armoured cable was in a 2 foot deep trench on a layer of sand with warning tape on top, and inspected before being re-filled. Special gland fittings are required at each end of the cable where it goes into weatherproof junction boxes (IP65/IP66).

 

While the trench was open, I also laid a couple of CAT5 exterior quality cables in it for Internet and telephony use.

 

 

[TheQ]

My usual advice to everyone is to:

Double glaze any windows with an additional sheet of perspex, it makes a surprising amount of difference, just leave a small hole at the bottom to let condesation out.

Put a damproof membrane down before you put the shed up.

Put a ventilator high up in the eaves, with a door on it you can shut, that can let the heat out in the summer, (if possible one each end of the shed).

Stop rodents from getting under the shed, I had rats eating through the floor before I had the roof on!!

 

I used jablite between the battons, and then used interior cladding to cover it over. All wood being sprayed with Anti wood worm liquid and allowed to dry before use (full protective gear worn)

The Shed "loft" is boarded over at cross beam height  (6ft 3inches at lowest height) and will be fibreglass insulated (just 'cos I got a load free). So my ventilator is boxed in and fed from below the ceiling..

All my electrics are surface mounted following the rules mentioned above.

I was lucky the power to the mobile home is on a telegraph pole.. 4 ft from the Shed 6 ft from the site of the new consumer unit.  I just needed 3 M of armoured cable.

Due to the likelyhood of SWMBO at one end of the shed me at the other, both with heaters on, and then SWMBO putting the kettle on. I ended up with two ring mains, her end and my end.. Plus Lighting which is either reclaimed fluorescents  or LEDs.

[RAF96]

I had a loft done out with the spray foam and it is lethal to unprotected iron and steel. Corrodes screws and nails and jointing plates. I was advised to paint over them all before the sprayers came, which I did. I also had to protect any cables as it is not PVC sheath friendly either.

 

Its not applied very thick and goes everywhere so don’t expect a neat and tidy job. I expected it to be 50 mm thick but it was about half that.

 

And did I mention expensive.

 

Moved house twice since then.

[TEAMYAKIMA]

I haven't been able to concentrate on the shed for a few weeks as other things have taken my attention, but back on track now...…………..

 

On ‎13‎/‎02‎/‎2019 at 13:38, Darwinian said:

I have used ecohome insulation in my shed. Much cheaper than cellotex and easier to put up. It seems to do a decent job, certainly kept the shed cooler in the summer but I’ve not had time to see how it fares with me in there in the winter. 

 

Anyone else used this? It looks easy to fit and cheaper so that attracts me.

 

On ‎09‎/‎02‎/‎2019 at 19:48, big jim said:

I insulated my shed with 25mm thick kingspan insulation between the uprights with a slight air gap behind them

 

Many people mention this air gap issue - why is it important?

[Richard_A]

The airgap is to give the structure a chance to breathe.

 

Timber can rot incredibly quickly if completely covered, check out your local building controls website, it will have a section on insulating rooves which should explain the importance of an air gap 

[TEAMYAKIMA]

Ok...

M shed now wired.

 

Next insulating......

 

Taking cost out of the equation , whic is better at keeping the shed cool in summer ... Rockwool or celatex? And is the difference significantly so?

 

 

I just can't make up my mind!

 

[big jim]

Can’t say I’ve tried rockwool but celotex kept my shed useable in the summer, it required heating in the winter though

 

of course rockwool will fill the void and leave you without an an air gap so the shed will be more likely to rot as already pointed out 

Edited April 10, 2019 by big jim

[Damo666]

17 hours ago, TEAMYAKIMA said:

Ok...

M shed now wired.

 

Next insulating......

 

Taking cost out of the equation , whic is better at keeping the shed cool in summer ... Rockwool or celatex? And is the difference significantly so?

 

 

I just can't make up my mind!

 

Celotex will have a better thermal value (Lambda value) than Rockwool for the same thickness. The lower the lambda value, the better performing the insulation. Rockwool varies between 0.035 - 0.038 w/mk, and Celotex GA4000 PIR board at 0.022 w/mk. Big difference.

Also, as Big Jim says, it won't give you an air gap, which would be a big problem.

 

If you need another reason: If you don't have an air-gap then the Rockwool will absorb some moisture, and act like a sponge. Then it would start to slump leaving uninsulated gaps at the top of the wall. And of course, wet saturated insulation against your timber isn't good news.

 

Make sure your air gap is ventilated at the top and bottom, to allow some small air movement.

Edited April 11, 2019 by Damo666
Rockwool Lambda value correction

[peach james]

I can only speak to ~10 year old BC (Canada) practices, but what it was would be from inside- outside:       sheeting (sheetrock):vapor barrier:insulation:wood sheeting:waterproof membrane:outer (water resistant) surface.  So, if you plump in rockwool in the cavities (which I used some of), then it is between 2 layers of "waterproof" seals, and the material in those cavities should stay dry at all times.  Again, that's with Type 5 house construction in BC, Canada, on the west (wet) coast.  

 

This does not appear to cause issues with moisture in the cavity walls, but it probably is NOT how the building you are talking about is built.   If both sides are not waterproofed, then issues may result.  The old style here was to use tarpaper as the waterproof membrane, but it has moved to Dupont Typar (?)  almost exclusively now.  I'd assume it is a 1 way breathable membrane, that encourages moisture to depart for the outside over time.

 

You can see the vapor barrier and insulation in this image: .  I have more photos on the laptop, but no good storage solution for them anymore online (Flickr's stupid rule change...).  No sheetrock because this is a unfinished basement :).  

 

James

 

[Damo666]

3 hours ago, peach james said:

.....  but it has moved to Dupont Typar (?)  almost exclusively now.

Do you mean Tyvek?

 

To the OP: Certainly what is needed is a Vapour Barrier on the inside and a Breathable Membrane (eg: Tyvek) on the outer side. This is so that any moisture that manages to migrate into the insulation has a chance of escaping out, and not get trapped within the construction.

 

Two points of note:

1. If moisture cannot escape it will condense within the wall construction (be that insulation, timber, blockwork). This is called Interstitial Condensation. Not good (having water form within the wall)!

2. No matter how well you install the internal Vapour Barrier, moisture will almost certainly pass through. Unless you are capable of exceptional construction by sealing all joints in the vapour barrier, along the floor junction and roof junction, make no penetrations (eg, for a wall socket, external light, TV aerial cable, shelving screw hole..... etc)

[peach james]

1 minute ago, Damo666 said:

Do you mean Tyvek?

 

 

One's for pants, the other for houses... there are times !

 

 

James