Tung oil to weather proof tongue and groove cladding

[opacey]

Hi all, I have a western red cedar clad large shed. I need to keep water out as much as possible. I'm a fan of tung oil and have already given the shed two coats but some water still penetrates through the T+G joints. What are your thoughts on this? If I add more layers of tung oil I'm sure I will make the wood itself impervious to water (if it isn't already) but how about those joints, will enough applications of tung oil eventually fill and seal the joints?

Many thanks for any advice.

 

[AronSearle]

No.

The cladding should be installed on battens to form a drained a ventillated cavity, it is not a boat, you can't make it watertight.

Lapped boarding is a bit more forgiving, much more air gets between the boards helping to dry them. This is why it is more commonly used on shed's (well, that and it is cheaper).

 

[opacey]

Ha, interesting points about the lapped profile of cladding.
Okay, I'll have to go back to the drawing board then, I was really hoping tung oil would be my magic solution here.

 

[AronSearle]

You can lather it in paint/stain (not varnish), something film forming will help provide more weather-tightness. Oil is too moisture permeable to offer any real water proofing for any decent period.

The problem with this solution is you need to go overboard, you need to maintain it, and if a lot of water still gets in then the lower breath-ability will mean more trapped moisture and shorter cladding life.

Good enough for a quick cheap fix, and it's a shed?

A proper fix is going to require you to remove and re-fit them.

 

[opacey]

It;s been rising steadily tonight (no wind, quite a large amount of rainfall) for the last few hours in London so I've had a chance to test the cladding's performance 'in the wild'. In a few places rain is coming through small channels such as around a couple of knots and some T+G joints. At no point does water form droplets, it is never more than damp spreading along the grain of the wood.

I like your point about film forming products keeping the water out (if well maintained) but also then trapping in any moisture.

It is indeed more than a shed, it's actually a garden room but I was trying not to complicate the thread. It's made of 6 x 2 studs at 400mm centres so is a very sturdy construction. The cedar on the outside is of course very durable.

Basically I can't rebuild it. There just isn't room around it for the battens and even if there was there certainly wouldn't be enough room for me to get in there to nail it (hammer room I mean). I've made the initial mistake and I'll have to live with it as best I can and I think that means cutting in covered ventilation slots everywhere to manage the moisture, using as much tung oil outside as I can and keeping the internal walls removable so as to check up on any problems as and when they may appear.

It was intended as a learning project and this is going to be my biggest lesson.

 

[opacey]

"It's been raining steadily..."