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What to do about shed rot?

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PeteWilliams

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I've been using a garden shed (built by the house's previous owners) as my workshop for a couple years and was about to insulate it. The walls were ply with a vapour barrier behind it, but just the studs and cladding behind that.

My plan was to stick a breathable membrane and kingspan between the cladding and the vapour barrier, but when removing the vapour barrier I can see the cladding is damp and starting to rot. Or at least on the first wall I've looked at.

I've only recently painted the external walls of the shed and I don't think it's coming from there, I think it's coming from the ground up - the rot is worse at the bottom, especially on one side - the corner where the gutter used to empty just onto the concrete below.

The shed is on a concrete slab and I think the wooden base is just sat right on it. To make matters worse, it's sat in an area of poor drainage, and there's often standing water around it, but the concrete slab is slightly raised from its surroundings, so I wouldn't have thought it'd be in that much contact with the water.

You can see some photos here: Workshop rot

I'm guessing the only way to fix this is to tear it down and start again, but is there anything I can do before I have the time/money to do that? Even if just to slow down the inevitable?

All suggestions gratefully received!

Thanks

Pete
 

Jameshow

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If it's the side and back walls which are poor I'd be tempted to paint with some of this stuff


That should stop the damp coming in for a year or two?!

For the floor I'd elvate it on engineering bricks to allow proper airflow.

Cheers James
 

TheUnicorn

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I would certainly raise it up, and run a dehumidifier if you can get power to it?

As to the next step, it would depend on how degraded the wood is IMO, and how sound the structure feels, essentially is it in good enough condition to spend money on?
 

PeteWilliams

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If it's the side and back walls which are poor I'd be tempted to paint with some of this stuff
But isn't the problem that the bits of wood that are soaking up the wood are the bits I can't access to paint? Ie, the faces in contact with the ground, and then the cladding edges where it's soaking from one board to the next, rather than the faces?

For the floor I'd elvate it on engineering bricks to allow proper airflow.
As in, try and jack up the building bit by bit and try and put the bricks underneath?
 
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PeteWilliams

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I would certainly raise it up, and run a dehumidifier if you can get power to it?
Yes, got one running in there now!

As to the next step, it would depend on how degraded the wood is IMO, and how sound the structure feels, essentially is it in good enough condition to spend money on?
It's… not bad, not great. The roof certainly needs redoing before too long. But I'd like to get another few years out of it. I spent much of last year building a double-garaged size shed/gym, and the year before that building a home office, so it would be nice to take a year off from building sheds!
 

artie

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What you have there is a garden shed, designed and built to hold spade, shovel and a wheelbarrow. Maybe a few other non perishable items which could survive out in the elements.
The single skin wooden walls keep most of the rain and wind out but allows some to come through. If left alone the rain will dry out again if weather permits.
Problem on these islands is that for months on end it may not get a chance to dry out. Adding that plastic sheet pretty much ensures that it never dries out, you can see the mould growing.
No doubt someone or somemany will disagree but imo the only way to have a snug dry shed is to allow some ventilation inside the outer skin so it can dry out and have another layer of insulation to keep heat in.
Also raise it a bit off the ground so that all the water can run off.
Don't put a dpm below any runners that you raise it on, people forget that it works both ways.
 

Sachakins

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Elevating on bricks is certainly the first way to try, as the process of leveraging it to put bricks will reveal either
A: the frame survives the attempt, in which case it is likely worth a bit more effort and cash on it.
B: the frame/panels creek crack and crumple, which means save your effort and cash to start afresh from scratch.
 

Jos7000

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If I wanted to extend its life with minimum fuss to structure. I think I would..
1. Rig up a small roof extension between the shed and the next building to limit rain fall on that end of the concrete.

2. Seal up any gaps in the cladding to try and stop ingress at those points. Using a butyl roof sealer.

3. Extend the bottom of the cladding down to within a few mm of the concrete/ground (not touching) to limit wind driven rain from going straight underneath.

4. If possible, create a small raised sealed bead on the concrete to push standing water away. Probably using some Black Jack to waterproof it.
 

Sandyn

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As well as a de-humidifier, I would run a large oscillating fan to help dry the walls and upper parts that have damp, also a bit of heat to speed up the process. I think there are years of life left in your shed yet if you do some of the work suggested.
Once you dry it out, get good ventilation to stop condensation. You can then see which timber needs reinforced and do patch work. Just nail timber in parallel. If some of the frame work is totally rotten, it will be easy to cut out and replace. A multi-tool is ideal for cutting out inaccessible timber.
For the rotten timber under the floor, an alternative is to see if it would be possible to hammer in replacements from the side. Taper the front end. I had one far worse than that and it stood for years with severe rot. Two foot of snow was the final straw.
 

Richard_C

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I've just added a year or two to the life of my #2 shed, hopefully it will last until I have cleared out other spaces and it won't be needed. But then, the clear out has been pending for 15 years.

It stands on slabs, bearer and bit of floor down one side rotten as we're the bottom inch or so of the side panel uprights.

I dug about a bit outside, used a crowbar to take some weight off then used a sledge hammer, brute force and ignorance to hammer a brick under each upright such that sound wood was sitting on brick and the soft rotten stuff was pushed aside. Then inside I notched out a bit of decking timber I had lying around so it fitted round each brick, screwed that to the floor along the edge that was on sound floorboards and from outside screwed the lowest wall bit into the edge.

Cost, a dozen or so screws and an 90 minutes. Lifespan? Who knows but hope will last through 2021 and I will do something proper or empty and demolish in nice warm weather the summer after.

It is mostly storage though, not a regular use workshop apart from a bit of potting up.
 

Jos7000

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Just thought of another, so...

5. After drying out all wood, you could use a low viscosity epoxy resin to prolong life by solidifying otherwise dodgy wood.
 
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