How is water getting in my shed ?

[DIY67]

Well I absolutely cannot fathom how water is getting into the inside of my potting shed which has been painted on the outside with Dulux Weathershield with no visible way on the outside where it is getting in. The very bottom of the tongue and groove piece is soft to the touch which again shouldn't be happening as I have given it 2 or 3 coats to account for splashback from the concrete flags the base is on. It never floods or pools. And yet inside there are wet patches in places that show it has been running down. The only thing I can think of is the nails (which now show rust) have created a weak point for water to seep ? Perhaps on a dry day paint over them with more weathershield making sure to seal the holes completely.

I had to take the images with a torch hence the poor lighting but you get the idea.



I

 

[Why Not Indeed]

It never floods or pools

Even if that's true, the flags are damp enough for long enough that you've got algae growing on them. Get the shed raised up, out of the moisture and let air flow around the bottom.

 

[foxhole]

It’s sitting in water which has travelled under the base .

 

[DIY67]

It's not from underneath, it's coming from higher up. You can see where water has trickled down. If it were from the ground up the whole shed would be affected. It's sitting on concrete flags.

 

[Alec_t]

You can see where water has trickled down.

Looks more like the timber has drawn the moisture upwards, by a wicking/capillary action.

 

[freddiemercurystwin]

T&G isn't waterproof.

 

[DIY67]

T&G isn't waterproof.

It is when painted with weathershield.

 

[Odds]

It is when painted with weathershield.

did you caulk the gaps with it?

 

[DIY67]

did you caulk the gaps with it?

No but as water travels down the overlaps I didn't think it needed it. Like roof slates

 

[freddiemercurystwin]

It is when painted with weathershield.

Clearly not.

Look up any detail where timber cladding is used on a wall, it will show a vented cavity behind it.

 

[Odds]

No but as water travels down the overlaps I didn't think it needed it. Like roof slates

Water always finds a way - and don't discount the effects of condensation.

 

[DIY67]

Water always finds a way - and don't discount the effects of condensation.

Water is lazy and always finds the path of least resistance

 

[DIY67]

Clearly not.

Look up any detail where timber cladding is used on a wall, it will show a vented cavity behind it.

Well yes but I would have thought as water doesn't travel upwards against gravity the vents would at least create airflow.

 

[freddiemercurystwin]

Of course it can, look up capillary action. Wind and differential air pressures can play their part too.

Any timber cladding is a 'rain screen' not 'rain proof'.

 

[Harry Bloomfield]

Well yes but I would have thought as water doesn't travel upwards against gravity the vents would at least create airflow.

It can, and does, by capillary action. Try leaving the bottom end/edge of a towel, in water, the moisture will wick up against gravity. It works with any absorbent material, like wood, which is why you should always set a hut, spaced up on none-absorbent material.