Problems with current shop

[woodsworth]

I guess this counts as a past mistake so hopefully some of you knowledgeable people can help me out with a solution.

My shop has a coloured Tin roof. One of the problems with that is condensation building up on the inside of it and the dripping that produces. I thought it a good idea to insulate it so i glued insulation boards to it. Problem is because the tin is not flat condensation still builds up and now it drips though the seems in the insulation and down the beams it is attached to.

What do others do with this problem? I thought about dropping the insulation and giving it an air space but the same would happen.

The other major problem is that the building was built with 8 inch blocks so i get a lot of damp coming through. What do people do in such a situation? I thought about knocking the whole thing down and building a workshop with straw bales but i need a place for all my equipment in the mean time and it''s not like i have a lot of money to throw at this problem.

Hopefully some of you have some creative answers that can help me out, thanks in advance.

 

[OPJ]

Sounds like some ventilation might help. If your workshop is long and narrow, two vents should help - one high, one low at alternate ends of the building. They will need X-amount of clear space surrounding them to get the best.

 

[Sportique]

Agreed Olly - you beat me to it

Dave

 

[woodsworth]

The shop is 20 feet by 40 feet. Where did you have ventilation in mind? It isn't all that air tight. I wish it was then i could work in there when it is cold! But even with a heater i can't get it to many degrees warmer then outside temp.

 

[matt]

Between your insulation and the roof but, by the sound of things, it's all glued together. Moist air must be getting trapped between the two.

 

[houtslager]

many options to this, but are all dependent on the size of your wallet :lol:

1. remove tin roof and repace with SIP panels
2. line i/s with "TYVEK" plastic sheeting with large overlaps and taped joints, then replace insulation under the tyvek.
3. put buckets in there to collect the water.

hth

k

 

[trousers]

Hi woodsworth

When you say coloured tin, do you mean the profiled and coated roof sheets?
In which case gluing insulation to the underside only has an effect on the flat parts, leaving the profiled parts uninsulated. Unless there is a lot of airflow through these profiled parts, thats where the moisture will condense.
As Houts has said, you probably need a vapour barrier like tyvek under the insulation. But I would strongly recommend that you have a ventilated airspace between the tyvek and the roof covering.
Or use the SIP panels for an all in one solution.
Either way, to do this properly you are looking at a re - roof if you want to end up with a warm space, especially if you can do something about insulating the walls as well.

Don't understand why your 8inch blocks are letting damp through. More info?

 

[Lons]

IMO as a builder you seem to have several issues:

If you are getting damp through the walls, you have moist air and this will condense on the underside of the cold roof as without adequate ventilation it has now where else to go. Are there eaves fillers in the profile where the roof meets the walls?

If the heater you use is not a dry heat (electric or oil filled rad) but is a calor heater or flame it will produce even more water vapour which = more condensation. (A calor heater produces gallons of water!)

You need to solve the wall problem:
If rising damp - inject a dpc
If penetrating moisture - paint the outside with Thomsons or similar or render it. or put up a breathable vapour barrier and fix 25mm slaters laths (you can fit 25mm polystyrene between if wished) and clad with plasterboard or ply.

Fit vents either end as high as possible to the roof to allow through ventilation and fit a breathable vapour barrier as others suggested.

Just one other point - check that no damp is entering through the floor.

Hope that gives food for thought

Bob

 

[would not]

How buildings cope with this problem that have steel linings and outer shells are to completely fill the void with insulation.
My mate has one of these tin sheds and the inside is like being in a shower with the condensation problem. The only solution is to put a sufficient thermal barrier between the cold roof and warm moist air inside the shed, leaving a WELL ventilated void between the roof and insulation.

It's a bit like the flat roof situation, cold or warm roof. The ideal situation would be to have 4" kingspan etc right up against the tin roof. Problem is the tin roofs tend not to be flat so you'll always have some moist warm air against a cold roof hence the water. If you can't get rid of the gap then you need to improve the ventilation to it.

Or another answer is insulation on top of the roof and then another roof on top of that.


Edit - you can buy tin roofing panels with the kingspan type insulation molded to it hence completely getting rid of the void.

 

[BradNaylor]

I had a similar problem at my last workshop - a corrugated iron roof.

I solved it completely by having the underside coated with spray foam insulation. That stuff doesn't come cheap but it is bloody effective.

Still cheaper than a new roof, though!

Brad

 

[woodsworth]

Thanks everyone for your advice. Its funny Brad that was the original idea, to spray it. When i learned it would be over a £1000 i decided to look for other options. I will have to go with the spray insulation.

Anyone know where the best deal is on that? I've found Xpandi foam has anyone used the kits before any tips would be appreciated.

As for the walls.

Don't understand why your 8inch blocks are letting damp through. More info?

To me it looks like the building was built with no foundation just a slab with walls on it. There looks to be a damp course between the slab and the blocks and that is about it. they used 8 inch blocks instead of using two four inch blocks with a gap in them. As i need to render the outside I am thinking that if i dig around the building and clean the walls and paint it with bitchimum paint and the thicker stuff where there is any honey combing, surround the building with a flexible drainage pipe covered with pea gravel and gardening fabric this will help with any damp getting into the base of the structure?

Then rendering it would stop any coming from the walls as people have suggested. I was also wondering if with these conditions if it is ok to build a stud wall inside with an air gap so i can insulate it or can i insulate the inside with the panels i will be pulling off the ceiling and board over them with plaster board?

I haven't ignored the suggestions provided just musing with the budget i have in hand, or will have over this year.

When you say coloured tin, do you mean the profiled and coated roof sheets?

Yes that is exactly what they are.

Edit - you can buy tin roofing panels with the kingspan type insulation molded to it hence completely getting rid of the void.

I've tried to find these, do you have any information, price on these?

 

[llangatwgnedd]

I used to have the same problem, I removed the corrugated sheets and laid plastic tarpaulin down as a sarking.

With the walls, these where cladded with timber on the exterior.

Problems solved.

 

[trousers]

Woodsworth

Reduce the ground level to 150mm below the dpc. This will stop any rising damp without having to do anything else.
If you have damp penetrating through an 8 inch block above the dpc your shop must be in a very exposed location. If it is that severe, then rendering the outside will sort it (waterproofer in the undercoat). Masonary paint finish.
DO NOT apply bitumen to the outside of the walls. An moisture within the building will be trapped. Let the walls breathe.
Insulate walls internally. Free standing studwork or battens fixed to the walls, with rigid foam panels in between. Not sure a vapour barrier is necessary - the rigid foam boards have a foil face which is a good enough vb in this instance, esp so if you use osb as a cladding (p'board not very resistant to knocks).

Re the spray foam. Be aware this stuff gives off highly toxic fumes in a fire and drips molten bits everywhere. It is not easy to clad over to provide a fire resistant lining.
My preference would be for one of the insulated roof panels, as Would not suggested. Kingpan do one, but there are others.

 

[Dibs-h]

Woodsworth

Re the spray foam. Be aware this stuff gives off highly toxic fumes in a fire and drips molten bits everywhere.

I thought the 2 part PU foams (sprayed) had some fire resistance?

 

[trousers]

Yes, some. A fire retardant is included in the formulation.

However, Building Regs state that all insulation materials should be installed behind a fire retardant barrier. The insulated roof panels have an internal lining for this reason, and to provide additional stiffness.

Woodsworth may or may not give a toss about the building regs anyway. He just wants a warm and dry workshop. You pays your money and takes your choice.

 

[Dibs-h]

Yes, some. A fire retardant is included in the formulation.

However, Building Regs state that all insulation materials should be installed behind a fire retardant barrier. The insulated roof panels have an internal lining for this reason, and to provide additional stiffness.

Woodsworth may or may not give a toss about the building regs anyway. He just wants a warm and dry workshop. You pays your money and takes your choice.

Ta!

 

[woodsworth]

DO NOT apply bitumen to the outside of the walls.

I'm just curious why you wouldn't apply bitumen to concrete below grade? Wouldn't you want to stop moisture before it gets into the foundation?

 

[trousers]

Err...... I'm sure you said the walls were built on a concrete slab and that you wanted to bitumen the walls......? I didn't say anything about applying bitumen to concrete.

[/quote]Wouldn't you want to stop moisture before it gets into the foundation?

You said the walls didn't have foundations.

Normally a wall foundation is a (several) rows of bricks/blocks built on concrete in a trench around the perimeter of the building, and below a horizontal dpc. It doesn't matter if these blocks get wet as the dpc stops it rising into the walls above (provided the ground level outside is nominally 150mm below thw dpc).
If your walls are built straight onto a concrete slab as you suspect and there is a dpc between the slab and the walls then the walls can only be damp if a) the ground outside is higher than the dpc or b) the damp is coming through the wall.
Normally slabs are used where ground conditions are poor/unstable, and t are usually reinforced with steel. The concrete specified for this construction is usually of very high strength and is vibrated when placed.
This results in very few voids in the set mix and it therefore inherantly waterproof.

So have you got damp coming up through the slab?
Have you got damp bridging the dpc at the wall/slab junction?
Have you got damp coming through the 8 inch thick wall?

Your problems are easy to overcome once we know what the cause of the problems are :lol:

 

[woodsworth]

I did a little jack hammering and trenching to clarify things, he did put a course of blocks under ground. So by your definition of a couple rows of brick being a foundation i guess it has one.

The other thing is my partner wants to put a raised bed on one side of the shop and want to paint the wall up to that point with the bitumen to protect it.

Where is the damp coming from? I haven't got a clue but I think through the walls and rising from the ground like everyone else who has damp problems. That's why i proposed the ideas i had to fix it, and why i asked why not paint bitumen on the outside of a wall. below grade, to clarify for you.

It still needs to be asked why you wouldn't put Bitumen on the outside when people also put a water proof rendering on the outside of buildings.

If i had time and money, i'd tear it down and save myself the grief. It is easier to start as a new build in my opinion then to fix something that someone has so thoughtlessly built. It's maddening!!! that such building get through. This one wasn't built without a permit, some hack built it so he could run a mechanics business from his home. Its just been there so long that they are accepting it.

 

[trousers]

If i had time and money, i'd tear it down and save myself the grief.

:lol: :lol:

Been there and done that :roll:

It still needs to be asked why you wouldn't put Bitumen on the outside when people also put a water proof rendering on the outside of buildings.

Bitumen (eg synthaprufe) type products are totally impervious to moisture. Any moisture within the building willbe unable to escape (except via draughts through doors/windows etc). It is good practice to let walls "breathe". The waterproofer admix in the rendering still allows this - it's a bit like a vapour barrier.

my partner wants to put a raised bed on one side of the shop and want to paint the wall up to that point with the bitumen to protect it.

Not desirable really. Apart from the above, synthaprufe type products need to be protected (against uv and mechanical damage) so if used externally you would have to take measures to prevent this happening.
Usually, if part of a structure was below ground level (and hence dpc) there would be at least a cavity, and probably a self adhesive sheet type vertical dpc to prevent damp entering the building.

Where is the damp coming from? I haven't got a clue

But how bad is it? Do you get a noticeable damp patch onte floor if you leave a piece of polythene weighted down a few days? Same with the walls? Are you sure it's not seasonal condensation (cycles of moist a nd dry air days).

I just think if you've covered all the bases I outlined in a previos post, then insulated, and got some heat (and ventilation) in there, a lot of your perceived damp may dissapear.