# Shed build with metal profile sheets



## Arnold9801 (6 Dec 2020)

I intend to build an 8m x6m shed with metal profile sheets. Last week a friend of mine outlined to me that he had built a shed from similar materials and was very surprised by the level of rust in there due to the amount of condensation on the back/inside of these sheets.

I found this a bit disheartening and was wondering if anyone else had found similar as it is a popular material choice for sheds and outside buildings.

I was intending on putting polystyrene sheets on the backs of them covered by OSB boards as an internal liner mainly to help with fixings such as shelves etc. Perhaps this may also eliminate the condensation issue as well?


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## kelsallcustombats (6 Dec 2020)

It might be worth looking at a vapour control layer, they use them in timber frame buildings, so could be useful in this instance. 






AirGuard® Control Vapour Control Layer 1.5m x 50m


An AirGuard® vapour control layer can significantly reduce heat loss and increase energy efficiency. By controlling heat transfer and reflecting heat inside the building, they help keep buildings cool in summer, and warm in winter. AirGuard® AVCLs offer highly engineered vapour control, to help...




www.travisperkins.co.uk


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## artie (6 Dec 2020)

I mentioned this in another thread.
When you order the box profile get the stuff with the non drip back, it's not much more expensive and worth way more than it costs.
Of course if you are going to insulate and line it then YMMV.
I just roofed with it no insulation.


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## Argus (6 Dec 2020)

Your mate is absolutely right - metal's brilliant for making tools......... 
But any part of it - inside or outside -that is exposed to air will collect water in the winter. As for the summer sun.......! Cornwall's famous for pasties, you'll be able to cook your own!

Seriously, I wrote a post just this week about being able to predict when moisture in the air will (and will not) condense on surfaces - an explanation of the process and how to measure air temperatures and try to avoid it. It was aimed mainly at tool conservation, rather than buildings but where it is employed in structures, particular attention is always paid to insulated vapour barriers.









Wet and Dry, a Little bit of Measuring...


There’s a lot of debate recently on this site (and others) around the subject of rust and its prevention on static hand tools – typically in unheated sheds and garages over the winter months. This has led to the dreaded words “Dehumidification”, “Dew Point”, then “Psychrometrics”….. yes...




www.ukworkshop.co.uk





Good luck.


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## Cabinetman (6 Dec 2020)

It also comes as a sandwich with three or 4 inches of foam in the middle for building walk-in fridges and freezers. It’s designed to fit together a la SIP construction. Not sure but I think it might be aluminium on both sides. Ian


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## clogs (6 Dec 2020)

insulated steel panels is what you need...u'll never get condensation...it's not cheap tho.....
try to get some used panels, always plenty around......
a simple steel frame of 100x50x3 or 4mm box is all u need...
plus a few Z purlins...over a 6m span I would use 4 purlins.....
even with a door or 2 plus the odd window.....the frame would take a 2 or 3 days or so to knock up...easy to do urself if u can weld.....!!!!!!
and 3 days would see it water tight......thats with 2 lads .....
[ I did an 11mx 7.5m roof in a morning with just 2 of us.....plus it was 5m high ]....roof panels were 7.5m long....
I make em up all the time......
the non drip coating is OK but u will still need insulation...best do it in one go.....
overall it will be slightly more expensive than a wooden shed but hardley worth the saving when u take into account the speed of the build and no maint needed.....
obviously u'll need a concrete base......and for that I'd be using some high density insultaion under the conc floor but over a Damp Course Membrane.....
my new shop much bigger will use RSJ's but will also get under floor heating......toasty toes.....hahaha....
if u want any help PM me....no probs....can send a few photos......


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## Arnold9801 (7 Dec 2020)

Thank you all very much for your replies. I suppose like most things my shed build is on a budget. It’s going to be from a timber frame. I have laid the concrete base last month which had a pvc sheet membrane underneath.

As I mentioned in my opening speel, with the polystyrene insulation on the inside of the metal sheets and OSB boards on top of that, do you think this would significantly reduce the level of condensation and moisture in the air?

Arnold9801


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## Jameshow (7 Dec 2020)

Should work.... 

I'd make sure the frame to to the edge of the concrete so that any condensation that does form doesn't pool onto the concrete and rot the base plate. Which I'd make out of treated timber. 

Cheers James


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## johnny (7 Dec 2020)

insulated profile steel is going to be hugely expensive for your given roof area 8x4m I'd go with timber and felt. Timber (ply sheets) is great for tying your walls together ,bracing your structure and is easier to work with to alter, adapt, fix to etc and allow a 5x yearly budget for replacing the felt . My 5x3m shed has a plywood and felt roof which has now lasted 6 years although there have been a few minor repairs needed with some damage from storm and high winds lifting the edge of the felt and a bit of heat blister here and there No problems with condensation in my shed workshop.


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## Arnold9801 (8 Dec 2020)

johnny said:


> insulated profile steel is going to be hugely expensive for your given roof area 8x4m I'd go with timber and felt. Timber (ply sheets) is great for tying your walls together ,bracing your structure and is easier to work with to alter, adapt, fix to etc and allow a 5x yearly budget for replacing the felt . My 5x3m shed has a plywood and felt roof which has now lasted 6 years although there have been a few minor repairs needed with some damage from storm and high winds lifting the edge of the felt and a bit of heat blister here and there No problems with condensation in my shed workshop.



Thanks for your reply. I intend to use the metal profile sheets just for the four sides. With a timber frame roof as well, I was going to use cement fibre roofing which I used on my main workshop 16 years ago and has been amazing.

Arnold


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## Hornbeam (9 Dec 2020)

Good morning Arnold. The day job is designing and testing metal cladding systems for Tata Steel albeit on slightly larger sheds.
There are a number if issues around using a single skin material. Steel is a very good conductor of heat and any moisture in teh air humidity is likely to condense out onto the back of the steel if the steel surface temperature falls below the dew point (which it will do).
To combat this you can take a number of approaches.

Reduce the humidity in the building by ventilation or a dehumidifier
Using a fleece backing does not stop condensation but it holds it in the fleece stopping it dripping. Once the temperature warms up again the moisture in the fleece evaporates. Personally I dont like this approach as you are treating the effect not the cause
Insulate and minimise contact of air within the shed with the metal sheeting including any cold bridges.
I would do both 1 and 3 (dehumidify).
Before speccing your insulation you need to define the construction method. Are you making a structural frame to fit cladding to with columns and rafters at each end with purlins between. For steel sheds, purlins are usually exposed on the inside but could be included into the insulation cavity.
Key issue is generating an internal air tightness later which well fitted OSB will do
Polystyrene is a cheap good insulation but it is very poor in fire. Much better to use a PIR insulation. Alternatively use glass wool but you will need about twice the thickness for the same level of insulation
External skin, trapezoidal sheeting can be laid vertically or horizontally. Horizontally looks less industrial.. Maintain an air gap between the insulation and the sheet but only has to be small, there is a lot of extra air flow in the deeper part of the profiles. Also for walls try and pec a wall profile (this has wider crowns and narrower troughs so looks better)
Foam composite panels use a PIR foam core sandwiched between 2 thin layers of steel. They are available in roof and wall profiles and although relatively expensive will make an extremely well insulated shed. One caution is that they are not great at sound insulation.
Make sure you fit a drip flashing to deflect water away from the base and the water can drain away from the base of the shed
Using fibre cement for the roof means that you will have a structure which behave similarly to steel with the fleece backing. Also note that most fibre cements are quite brittle so easy to crack during installation and the roof would be fragile so shouldnt be walked on.
The roof can be made with steel profile in exactly the same way as the walls.
A cautionary note on painted steels. It can be quite difficult to tell the differences in quality of sheets just by looking at then. The cheapest polyester coating have very thin zinc coatings under the paint and you will be lucky to get a 10 year guarantee . At the other end the best sheeting will have a thicker (8 to 10 times as thick) plastisol coating and will use a zinc/aluminium alloy as the protection for the steel. This coating almost totally eliminates corrosion at exposed cut edges. The other big advantage of plastisol is it is much more robust and scratch resistant.
If you have any questions drop me a pm
Ian


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