Water seeping through knots in summerhouse log wood

[Alonso100]

I have spent the best part of 10k on a summerhouse for the garden end of last year which I didn't use during the winter as I still had to furnish inside. I noticed a few months ago the bottom strip on the inside had turned black most of the way round which then revealed small pools of water every time it rained, the roof is fine as the water is coming through when I aim a hose at the side. Much of the tongue and groove isn't tight so assumed that was the issue so went round every gap with CT1 silicone, also filled every gap at the nails with Woodfiller.... still coming in.
I have now removed 1 sheet of ply and the insulation from the inside to see where it was coming in and it is actually seeping through the knots, not just 1 but about 10 knots just in that small section alone.
I bought everything myself and paid a joiner to build it so don't have any comeback on the builder, so just a few questions.

1) has anybody came across this before?
2) do I have any comeback on the company who sold the log lap for selling inferior wood possibly not quality checked?
3) how do i fix it without rebuilding it with new log lap, ie anything that would seal it?

 

[Alonso100]

Just to add, I have contacted the company who sold me the timber and waiting on them getting back to me, just wondered what my rights were in case they try to fob me off.

 

[Mike13]

You need shellac based knotting sealer to start with, the resin that comes out of the knots pushes away the paint from the inevitable cracks in the branches poking sideways through the planks. shellac seals it in and fills the cracks.

 

[Alonso100]

Problem I have tho is there is probably hundreds of knots seeping water and without stripping all the ply and insulation from the inside I cant specifically see where every knot is with an issue so I would maybe need something I could just paint over the outside, I have already applied the Osmo oil preserver which obviously hasn't done much good. What about a yachting varnish?

 

[JohnD]

Post some photos please. Show the entire wet wall(s) from the roof down to the ground. The eaves, gutters, downpipes, and the concrete pad the building stands on, are particularly important.

You mention pools of water at the bottom. Show this area, inside and out.

Paint and varnish will not fix it.

I don't actually think knots are the fundamental problem.

No doubt the T&G was placed with the tongue facing upward.

 

[Alonso100]

Its defo coming through the knots, there is 1 picture you can clearly see the drip forming just under the damp knot and its dry all around it so cant be coming from anywhere else.
The pools of water are forming as the water eventually runs down the inside to the bottom and you can see where the timber has turned black over time.
Yeah the t&g is facing upwards.

cheers

 

[freddiemercurystwin]

Timber cladding of any kind, if it is to be used on a habitable building (or one that wish to remain dry inside) must always be treated as a rainscreen rather than rain barrier. A breathable membrane should be applied to the outer face of the studs, then the membrane then battens (which creates a cavity that's vented top and bottom) and then the cladding. Any rain that penetrates through the cladding can then run down the cavity and out or just evaporate.

 

[Alonso100]

Not really sure what you mean, the log lap was supplied treated and i also applied 1 coat of Osmo uv protection oil.

 

[freddiemercurystwin]

What these suppliers should be saying is that the cladding might leak then.

 

[Alonso100]

Sorry, still dont get your point, why would they say it would leak. Nobody in their right mind would spend nearly 10K building something that needed to be waterproof if there was any chance they were buying material that wasnt?

 

[freddiemercurystwin]

Unfortunately there's a disparity between how water proof a summer house with merely a timber rain screen cladding is and how waterproof a proper building that has the right wall build-up will be. They have your money now and will blame the wood, the fitter, the knots, the treatment everything but the real answer.

 

[scbk]

Sorry, still dont get your point, why would they say it would leak. Nobody in their right mind would spend nearly 10K building something that needed to be waterproof if there was any chance they were buying material that wasnt?

It would be fine if you had the cladding exposed on the inside (like a plain summerhouse/shed). But with having the building lined/insulated it should've been built with an air gap/cavity/breathable membrane. 10k is nothing these days, I know someone who spent that on a yurt+deck, basically a big tent!

 

[JohnD]

I particularly asked about the eaves, gutters and downpipes, and the edges of the concrete slab.

 

[Alonso100]

I don't have gutters or downpipes as the roof runs to slight angle to the back, I've checked with heavy rain and there is minimum water runs of the sides, it all runs to the back, although I am going to fit a gutter and pipe at the back.
The summerhouse has been built on stilts, 22 of them.

I don't believe the issue lies anywhere other than the knots as I have even tried aiming the hose on a few boards at a time and you can see the water seep thru instantly.

 

[freddiemercurystwin]

Knots or joints the timber cladding is not and never will be rain proof.