Steel Shed: Weather tightness options?

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tchart

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#195224 11-Apr-2016 11:31

Just finished putting up a new shed which is on a (new) concrete base with a rebate.

I noticed the other evening that the inside of the roof was covered in condensation. I did a bit of research and this seems to be caused by excess moisture in the shed. I'm hoping this is just because of the newish concrete base which has probably not completely dried out yet. Has anyone experienced this before?

The shed is to be a primary outdoor storage location (as we don't have a garage) so I'd like to improve the weather tightness. I don't expect it to be 100% water tight but has anyone got any suggestions on how to improve the situation?

Current issues I've identified;

1) The shed roof has gaps where the roof meets the walls. There is an overhanging eve but there are gaps that would let air in.

2) Where the shed walls meet the sheets overlap (at the corners of the shed) but there is a gap as they are not screwed together. The instructions suggested filling these with some kind of compound.

3) The doors are not water tight

Anyway, I was thinking of using expanding foam to plug up some of the gaps. Good/Bad idea? Any better ideas?

Thanks

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#1529988 11-Apr-2016 11:36

If you plug all the gaps, and put something in there that has moisture in it, it will not dry. I would have thought a tiny bit of airflow would be good?

How well sealed is it to the base? In our last house, that's where water came in, from the base if it got really wet.

You could look at a bit of dessicant (Damp Rid or similar - maybe even that synthetic cat litter?) to absorb moisture, and seal it up as best you can

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#1529990 11-Apr-2016 11:45

All tin roofs have condensation from time to time. That's partly what the builder's paper is there for so the moisture can run down the paper to the outside. Airflow is your friend for this as trig42 suggests, carrying some of the moisture away.

Any stuff you need kept dry, raise it off the floor (e.g pallets which can be found on the kerb in industrial areas when the company has finished with them) and ensure there is a bit of airflow beneath it (pallets for example) and loosely cover it in plastic to prevent drips (but still allowing some airflow).

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#1529993 11-Apr-2016 11:49

There is probably moisture and heat coming out of the concrete still, which will stop eventually. Try leaving the door open as much as you can to get airflow. The gaps are necessary to permit some airflow, this will actually remove moisture more than anything.

tchart

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#1529997 11-Apr-2016 11:54

Thanks guys!

The concrete base has plastic sheeting underneath the concrete pour. Its just over a week old so I do suspect its not finished drying. The pad is raised and rebated so I don't think moisture will get in that way.

Ill keep the door open for now and report back.

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#1529998 11-Apr-2016 11:55

yeah concrete takes a good month or more to fully dry out

mattwnz

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#1530061 11-Apr-2016 13:42

Really you should wait a month before enclosing a concrete slab, as it is releasing a lot of moisture. You will get a condensation afterwards too, but that is why you line it with building paper before you put on the cladding.

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#1530088 11-Apr-2016 14:47

+1 on the floor being the likely problem. Current one we wanted to avoid any permitting issues so installed on a timber ventilated platform. Everything inside stays nice and dry, even with gaps everywhere. Previous one on a concrete floor was about 3-4 months before condensation reduced. It never fully disappeared

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tchart

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#1530093 11-Apr-2016 14:58

scuwp: +1 on the floor being the likely problem. Current one we wanted to avoid any permitting issues so installed on a timber ventilated platform. Everything inside stays nice and dry, even with gaps everywhere. Previous one on a concrete floor was about 3-4 months before condensation reduced. It never fully disappeared

Interesting. I would have thought a concrete pad would've been best. Our other smaller shed is currently just sitting on top of some pallets. I think I might just build a timber pad for that one then.

mattwnz

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#1530146 11-Apr-2016 18:06

ubergeeknz:

yeah concrete takes a good month or more to fully dry out

Takes a good month to get most of it's strength too. But you see builders erecting framing after only a few days after install.

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#1530211 11-Apr-2016 20:28

Gaps at the top = good for ventilation.

Gaps at the sides = let rain in.

They'd have to be bl00dy big gaps to use expanding foam though! Silicon is probably your better bet. Note that most clear silicones you can't paint, so if you want to paint it, make sure you pick a paintable option (which probably won't be clear). Most (all?) expanding foam I've seen is also for internal use as the UV doesn't do nice things to it.

If you're still having condensation issues once the pad had fully cured, you might need to install some additional vents. If you've got a peaked roof/eaves (that will stop the rain coming in), a vent (or series of holes if you want to keep it easy) at either end will help the airflow. Otherwise you can get rooftop vents, but you'd probably want a plumber/roofer to flash them properly so probably pretty overkill for a tin shed.

Finally, is the base of the shed bigger or smaller than the concrete slab (i.e. does the floor sit inside the walls of the shed or not)? Some tin sheds I've seen are built on a concrete slab bigger than the footprint of the shed. So rain falls on the slab and promptly runs under the walls. Even if you lift stuff up off the floor, the water will still run inside and evaporate and cause you moisture issues inside (unless your slab is wonky enough that the water will run in one side and right out the other). Again, some decent sealant around the base might be in order.

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tukapa1

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#1530380 12-Apr-2016 06:50

tchart:

Just finished putting up a new shed which is on a (new) concrete base with a rebate.

Out of interest, what brand shed was it? I'm just halfway through the process with a shed from TradeTested, and there's been issues.....

tchart

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#1530389 12-Apr-2016 07:12

tukapa1:

tchart:

Just finished putting up a new shed which is on a (new) concrete base with a rebate.

Out of interest, what brand shed was it? I'm just halfway through the process with a shed from TradeTested, and there's been issues.....

Oh no @tukapa1, what kind of issues? Mine is also a Tradetested one - this one to be exact

I must admit that in some cases the instructions are less than clear. Happy to share some of my experience with you.

tukapa1

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#1531044 12-Apr-2016 20:22

tchart:

tukapa1:

tchart:

Just finished putting up a new shed which is on a (new) concrete base with a rebate.

Out of interest, what brand shed was it? I'm just halfway through the process with a shed from TradeTested, and there's been issues.....

Oh no @tukapa1, what kind of issues? Mine is also a Tradetested one - this one to be exact

I must admit that in some cases the instructions are less than clear. Happy to share some of my experience with you.

Firstly it was damaged during transit/delivery, the box was ripped and the wall and roof panels were bent and creased.

I emailed them about it and while Frances was always polite and made the right noises, they kept asking for more photos, and then more photos until I got sick of waiting and bent the panels back into shape the best I could. There are only so many photos from so many angles you can take...

Also whoever delivered it left it in our front lawn in view of the street while we were out of town for 48 hours, even though they said they would contact us before delivery as they needed assistance to unload (maybe that's why the package was damaged).

I agree that the instructions aren't particularly clear in some places but I've muddled my way through putting all the wall and roof panels together.

I also put down a concrete floor with 25mm rebate as per their instructions, but I have found the corner brackets that go on the floor, allowing the walls to go up and join in the corner, are diagonal and do not fit within the rebate area, unless I'm missing something. So I'm either going to have to cut an angle out of each corner of the pad or cut the corner brackets to fit.

I was a little surprised how flimsy the metal was, but accept that you get what you pay for and I knew I would be compromising when I bought it at the price it was. I will purchase framing timber and will reinforce the shed with framing inside all around. I may even line the walls with ply once it's framed. That should give it some support so it doesn't blow down in the first strong breeze.

At the price it should do the job but it hasn't been the best experience I've had support wise lately (that would be Fitbit, but that's an entirely different thread....)

tchart

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#1531374 13-Apr-2016 09:51

Mmmm thats not good.

I must say that our shed was around 130kg and I could not move it. The original freight company dropped it off outside our garage and it stayed there for a couple of months until we moved. The moving company moved it and I think they dropped it as some of my sheets were bent on the edge. Some of the panels had scratch marks on so that was disappointing - given they are all covered in plastic.

As for your other comments I had the exact same problem with the corner fixings. I just swapped them around and put the "bottom" ones on the top etc. I was going to email them back about that as it doesnt make sense especially when they recommend "strongly" having a rebated concrete base. Also the floor fixings can't be used on a rebate either, so WTF!

I found the instructions a bit hard to follow at times (especially the roof) and also there are many things in the bag of bits that seem superfluous - e.g. why are there rivets when they aren't shown in the instructions. Same for the plastic rings, I assume these are meant to go on the screws but I only figured that out after I was 80% finished (again not mentioned in the instructions).

Also I found there weren't enough screws so I had to go and buy extras!

In terms of quality, I think the quality isn't bad. My other smaller shed is a standard one from the Warehouse and I'd say the Tradetested one is much better quality.

tukapa1

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#1532703 13-Apr-2016 19:22

tchart:

Mmmm thats not good.

I must say that our shed was around 130kg and I could not move it. The original freight company dropped it off outside our garage and it stayed there for a couple of months until we moved. The moving company moved it and I think they dropped it as some of my sheets were bent on the edge. Some of the panels had scratch marks on so that was disappointing - given they are all covered in plastic.

As for your other comments I had the exact same problem with the corner fixings. I just swapped them around and put the "bottom" ones on the top etc. I was going to email them back about that as it doesnt make sense especially when they recommend "strongly" having a rebated concrete base. Also the floor fixings can't be used on a rebate either, so WTF!

I found the instructions a bit hard to follow at times (especially the roof) and also there are many things in the bag of bits that seem superfluous - e.g. why are there rivets when they aren't shown in the instructions. Same for the plastic rings, I assume these are meant to go on the screws but I only figured that out after I was 80% finished (again not mentioned in the instructions).

Also I found there weren't enough screws so I had to go and buy extras!

In terms of quality, I think the quality isn't bad. My other smaller shed is a standard one from the Warehouse and I'd say the Tradetested one is much better quality.

Yep - they're not light - we have the 3.45 x 2.6m jobbie in ironsand. I had to unpack it and move it in parts to get it into our garage.

The plastic is a real pain to get off - I started on one panel then flagged it - the plastic can stay on as far as I'm concerned.

I'll have a look at swapping the corner fixings around. If that worked for you then hopefully I'll be able to make it work. I need to get this thing up so I can move some stuff in from my garage.

Having not finished the construction yet, I was confused as to why there were rivets. I couldn't see anything in the instructions calling for them. I also had most of the panels built before I came across the bag of little rubber washers, which I presume are supposed to go on every screw. No mention of that in the instructions....

I'm dreading the roof now, if that's the most confusing part of the instructions.

Good to know about the quality, although I will definitely frame it inside once it's up. It will give me piece of mind, and if I pay an extra $200 or so for framing timber it will still be a cheap shed.

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