Pressure treated vs surface preservative.

galljga1

Hi folks, I am in the process of buying a new wooden garden storage shed. I want something decent that is going to last 20 + years. I have been told by one supplier that they apply two coats of preservative to the timber and that this is as good as pressure treated timber. Conventional wisdom or at least what I have been led to believe is that pressure treated is a superior product. On the other hand I have heard from one neighbour that pressure treated fencing that he bought rotted where it exited the ground after about 8 years.

So....
Which is best, pressure treated timber or timber that has had two coats of preservative applied?
How do you know that claimed pressure treated timber is actually pressure treated.
If pressure treated timber penetrates the entire piece with preserving chemicals, why are we told to apply preservative to the exposed piece if the timber is cut?
How much more would you expect to pay for a pressure treated loglap or shiplap shed over the same shed that has had two coats of preservative applied? Dimensions 14 feet by 10 feet.

To anyone answering, I know nothing about the longevity of various types of timber. Please confirm whether, like me your answer is based on what you have been led to believe or is it based on working with timber over a period of time.

Apologies if this is the wrong forum. I wasn't sure whether Gardening or Woodcraft was more appropriate.

Cheers All.

Miname

Either one is as bad as the other at lasting. It's the type of the timber that more important and it's whether you go out and treat it every year.

galljga1

Miname wrote: »

Either one is as bad as the other at lasting. It's the type of the timber that more important and it's whether you go out and treat it every year.

Yeah, that is what I am coming around to believe: initial treatment will provide some protection but regular treatmant is the key.
What timber do you recommend?
What timber would you stay away from?

Cheers

kadman

Steel post sockets in concrete, and keep the wooden posts out of the ground.
But the additional expense has to be considered. Or larch stakes.

galljga1

kadman wrote: »

Steel post sockets in concrete, and keep the wooden posts out of the ground.
But the additional expense has to be considered. Or larch stakes.

Cheers Kadman. It is actually for a shed. What do you think of spruce for this purpose?

enricoh

Get a shed with steel cladding on the roof, this will add a good few years onto the life of the shed compared to the felt type crap most of them use

kadman

galljga1 wrote: »

Cheers Kadman. It is actually for a shed. What do you think of spruce for this purpose?

Spruce is non durable. Any timber in contact with the ground and elements
is going to degrade.

Unless its a durable species.

galljga1

enricoh wrote: »

Get a shed with steel cladding on the roof, this will add a good few years onto the life of the shed compared to the felt type crap most of them use

Yeah, steel cladding is what I will be getting. My main concern is actually the subframe. You cannot get at this once the shed is erected. Is this one of the main points of failure? My shed will be on a sandstone paved area which does not retain water but you would have to assume the subframe will be subject to absorbing water in inclement weather.

galljga1

kadman wrote: »

Spruce is non durable. Any timber in contact with the ground and elements
is going to degrade.

Unless its a durable species.

So, do you know any firm that builds wooden sheds from durable species or is that cost prohibitive?

kadman

Depends on your main criteria.

Is it timber first, or durability first.

Galvanised materials and pvc are more durable , and maintainence free
than most timbers.

kadman

Galvanised subframe.

galljga1

kadman wrote: »

Galvanised subframe.

Yeah, didn't think of that. However, I have not come across a manufacturer who builds wooden sheds with a galvanised subframe. Even some of the steel sheds I have viewed looked like they have a wooden subframe (I think, I can't be certain as it was not something I was looking out for). Personally, I prefer wooden sheds. If I could source one with a galvanised subframe, It would probably be the best of both worlds.

my3cents

Some of the poorest quality timbers are fine for shed building if pressure treated. The reason is the really poor quality timbers are faster grown which while gives poor durability gives much more soft growth that can soak up masses of preservative.

Pressure treated every time my sheds are getting on for 15 years old but I wouldn't expect coated timber to last as long.

If you really want to protect a pressure treated timber shed then leave the shed a year to weather then treat with clear Owtrol Textrol and recoat every 4-5 years. Expensive but works.

The problem with a steel shed is condensation unless you go for the expensive insulated sheeting.

kadman

galljga1 wrote: »

Yeah, didn't think of that. However, I have not come across a manufacturer who builds wooden sheds with a galvanised subframe. Even some of the steel sheds I have viewed looked like they have a wooden subframe (I think, I can't be certain as it was not something I was looking out for). Personally, I prefer wooden sheds. If I could source one with a galvanised subframe, It would probably be the best of both worlds.

You may as well go full tilt on a shed comprised of all galvanised frame, pvc or steel cladded exterior, and standard profile roof sheeting.

If maintanance and long lasting is what you are looking for.

Or get a galvanised subframe ordered, and attach a wooden shed to it.