Built up a pretty substantial workspace / log cabin for my misses a month or so back and due to the cold and wet weather we just cannot get it watertight. Right now we have tarpaulin round all 4 corners.

There are 2 edges that seem to be are worse than the rest. Should i even bother trying to paint it when the weather is dry or just leave the tarpaulin in place till next year when the paint might actually have time to dry properly.

I just do not want the wood to rot over the winter.

why is it leaking ? just permeating the wood or are there gaps its getting through ?

is it a kit or home brew ?

Sikaflex is going to be your friend here. Look for a paintable, probably clear (for external) finish. As soon as it looks dry enough, get squirting. There will still be some residual damp, but that’ll dry out as the weather gets better (that’s just wood for you)

If you’re worried about rot, get some treatment on there sharpish as well.

Did you do any treatment on the wood before assembly?

It was a kit, 32mm thick batons. The 2 corners that are getting the damp problems have had a couple of coats of paint but i don’t think it managed to dry properly before the rain got to it.

The wood is untreated pine and is about 95% watertight and coated by us, its just a few problem areas on the corners.

If it’s normal paint, that’s not going to waterproof it. Most paint is micro pourus so designed to let moisture transfer through it.

Can you link the kit so we can see the build up?

No it’s this stuff

we were told when we bought it that it would completely waterproof and protect the wood. It is working fine on the main sides just these 2 corners. Ill keep the tarpaulin in place i think as keeping the wood rot free and dry is the most important thing at the moment.

I use a lot of paint on external timber products (paint bill last year was £300k plus labour). We use a high end external paint, and I’ve never yet used it as a water proofer in a joint. Yes, on a surface, but even then the moisture content of the wood will go from about 12% in the summer to 20% in the winter. showing that water does transfer across the paint system. There’s nothing you can do to stop this, it’s part of the nature of wood. It’s also nothing to worry about.
In a joint, you need something more than paint. This is why I advised sikaflex.
Oddly, you will encourage rot if you wrap the wood up. Water will still get in, then can’t escape and dry out, creating the damp enviroment rot develops in.

if its a joint then yep . paintable sikaflex/tigerseal is the way to go.

Thanks tinybits, advice all appreciated. I had a look at sikaflex and will get some ordered 😀

If it’s leaking there must be a design or build issue. Most wooden buildings, if designed and built with overlaps anywhere there is moisture, will be waterproof by design. Sealant just helps it stay dry if water ever does get in (driving rain etc).

You need to have a look at the area above those leaky bits to see how water can be diverted away.

thats why i asked if it was a kit large418.

most kits ive worked with – admittedly poor quality have had poor corners- usually 2 battons in the corner with unsupported cladding creating the actual corner form (make em easy to assemble – for them rather than the consumer im sur – nee easy to make square as they never are as they come)

Without seeing the actual design it will be hard to tell, but one thing is for sure, it should be watertight without having to use a paint product over the wood.

The one I built was probably a bit bigger than yours ( 180 M^2) but the principle are the same. Did you use waterproof gaskets between the logs ? How hard did you bray the logs together and is there threaded rods to tighten to close up any gaps ?

I dont like to be negative about this kind of stuff as there is always a way to fix this sort of thing but it may mean taking the roof off and re doing the leaking logs. another alternative would be to use a membrane on the inside ( Tyvek or similar) and then re clad the inside, doing this you would need to prevent as much water getting the join as possible, but the logs would be able to control the moisture fairly well and you would have a dry space inside.

Righog, the batons were tongue and groove, the corners are interlocking which made for reasonably easy building and it seemed from my very amateur point of view to be well built. Weirdly the damp patches on the inside of the corners are not coming from the top. The are in patches around halfway up. thats why i thought it was not enough waterproofing on the outside.

This is the slighly smaller version. Cabin

I’ve recently built something similar. I’ve had no problems with damp at all. Not had a chance to varnish it yet as the bad weather took hold.

Was the base absolutely flat & properly tamped down before you started? Does it have storm braces and if so have you tried slackening them off leaving it for a couple of days & then re-tightening them? This might allow the logs to re-settle, sealing the T&Gs.

AFAIK Curpinol shades isn’t a paint – it’s a staining preservative so has no, or very little waterproofing qualities. It’s basically designed to stop wood from rotting and prevent insect infestation.

Thanks MTK.

It’s not good that it’s half way and not at the top.

Why I asked how hard you Brayed the logs in ( Hammered them together ) is that this really does seal the joints ( there will always be some movement in the wood)

One trick I saw used was to get a really big ratchet strap off an artic and put as much tension on the joints as possible to close any gaps in joints.

If it’s leaking there must be a design or build issue. Most wooden buildings, if designed and built with overlaps anywhere there is moisture, will be waterproof by design.

Although you cover yourself well by saying “most”, I wouldn’t necessarily agree. Due to the very nature of timber and its potential to move and absorb moisture, a lot of ‘sheds’ and ‘garden buildings’ are likely to allow rain to pass, especially under extreme wind-driven heavy rain conditions. The T&G rebates are rarely sufficient alone and if you want a waterproof structure you need to do extra work on erection as tinybits suggests.