Questions re treating new rough sawn shed

PhotoMan

Hi,
I wonder if there  is anybody with some expetise and/or personal experience regarding sheds.
We have just had a shed erected in our garden made of rough sawn tanalised wood. Because of the almost continuous wet weather of late it is of course very wet inside and out (it was erected in the rain).
As I write I am drying out the inside with a dehumidifier.
My questions are
1. As I am able to dry the inside to a degree, before the outside, should I put preservative/garden paint on the inside?
2. Is this a good idea or a bad idea?
3. Given that the weather is so fickle at the moment, how many consecutive days of dry weather would we need for the outside to dry before having preservative/paint applied.
I'm very aware that I could create problems down the line if I trap moisture in or outside of the shed. So I want to get this right, from the start.
I'm just concerned that it seems that we are unlikely to have a prolonged stretch of dry weather in the near future.
Thank you to anyone who can help. It is much appreciated.

Albermarle

Normally the advantage of having tanalised wood is that you do not have to treat it ( if you don't want to)
It has been pressure treated with preservative already.
That is what I understand anyway.

FreeBear

Leave it until spring or even summer when the timber will dry out. No point in running a dehumidifier inside the shed - Sheds are naturally draughty, so there will be a steady stream of moist air coming in from outside. Turn the dehumidifier off and save money on the electricity bill to put towards paints & stuff in the summer.

Section62

PhotoMan said:

My questions are
1. As I am able to dry the inside to a degree, before the outside, should I put preservative/garden paint on the inside?
2. Is this a good idea or a bad idea?
3. Given that the weather is so fickle at the moment, how many consecutive days of dry weather would we need for the outside to dry before having preservative/paint applied.
I'm very aware that I could create problems down the line if I trap moisture in or outside of the shed.

As Freebear says, wait for the Summer for the wood to dry out naturally and thoroughly before applying anything else.  There's no point using a dehumidifier.  The shed shouldn't be so air-tight that a dehumidifier would be effective.

If the inside of the shed is still 'wet' more than a couple of days after it was put up (in the rain) then it suggests either there is something wrong with the way the shed was put up (which is allowing the rain to get in) or you have some kind of condensation problem.

As a general rule it is a good idea to leave the inside face of timber walls with only minimal treatment (e.g. woodworm protection), which tanalising will achieve.  That helps allow the wood to 'breathe' with water vapour being able to escape with natural fluctuations in moisture content through the year.  If you cover both faces of boards with a non-porous finish then you are likely to end up with bubbles in the finish, which leads to cracking, and ultimately failure of the finish and rotting wood.

PhotoMan

Thank you all for your helpful advice.

Lorian

Definitely don't paint inside. My favourite product on rough sawn sheds is ducks back put on with big soft brush. but others will have their favourites. Tricky now as you need it to dry for several days before painting and be dry for as many hours as possible.

ThisIsWeird

As others have said, PM, don't do anything about your shed until you have a solid period of dry weather. It's a new shed, tanalised, and will come to absolutely no harm meanwhile (unless it's been constructed incorrectly, like a leaking roof).
At some point you can research what type of ongoing protection you'll want to give it. Your essential choices are to either 'coat' it in a decorative finish that'll also help prevent rain from penetrating, or to 'soak' it in preservative which can also have a decorative tint in it.
Pros and cons.
The 'coat' - eg Ducksback, Garden Shades, etc - will probably look best, but will require recoating every few years, and all it does is provide a 'skin' to try and keep out water penetration. If that skin is breached or incomplete - and at corners, door & window frames, and joints it most likely will be - then rain will keep getting through at these points, and will eventually overwhelm the tanalising. You will then almost certainly get rot setting in - tho' it'll likely take a decade or so. It's almost impossible to effectively fully 'skin' and waterproof a shed using paint! And if the coating starts to blister or peel, then you have a significant decorating/protecting job on your hands.
The other option is to use a preservative, which is effectively what 'tanalising' is, although not under pressure. So, you'd be adding to the existing preservative, replenishing it, and compensating for it being gradually washed and degraded by rain and weather, but - more importantly imv - adding fresh preservative where it effectively didn't and doesn't exist at the moment. By that I mean on the ends of any cut pieces of timber - and there will be dozens of these on your shed, currently effectively untreated.
So, I'd give a new shed at least 6 months (even a year) to 'weather' (Ie, have its factory-fresh outer layer more receptive to a new application), then a good few weeks of continuous warm & dry weather so that the timber is bone dry, and then I'd soak it in fresh preservative, concentrating on corners, door and window frames, joints in the planks, the bottom few planks, and any exposed floor timbers underneath. You can apply it liberally with a brush, or spray it (non-solvent types) using a garden sprayer - the latter will get it right into cracks and gaps. Consider how rain falls and runs down the sides, where it pools, lands in frame joints, etc, and load these areas with preservative so it goes in where future rain will want to.
Allow to fully dry.
How to finish? Depends on what colour you are after, but I would stick with a tinted preservative, so it keeps soaking in and retreating the timber.
In essence, one method ('paint') tries to keep water out (and will not fully succeed), and the other just stops the timber from rotting.
There are also some soak-in preservatives which have a decorative tint - typically shades of brown or green - so look pretty good, but they also have a water repellent in them. So it doesn't look like a 'coating', but still shrugs off water. I suspect that they might be the best overall bet.
Whatever you go for, remember to imagine the rain landing on your shed and making it's way down the sides - focus on all the water 'traps', as that is where the water will try and start the rot. Also the bottom planks - that's where water will gather to drip off, and is by far the wettest part of the shed.
Happy New Shed.

PhotoMan

ThisIsWeird said:

Pros and cons.
<SNIP>

That must have taken ages to write. Thank you for that detailed and comprehensive reply.