Would this protection for a shed be OK?

[Lucky Luke]

Hello, experts. In our garden, there is a 12ft X 8ft work-shed. In previous years, when I was much fitter than I am now, I would coat the walls etc. with Cuprinol or Ronseal. Both of these have become very expensive — especially Cuprinol. Besides, Ronseal demands two-coats if it is to work properly. In my old age (83), even to apply one coat would be too much work, and to arrange with someone to do this and pay them for it also has difficulties. (For one, I could not decide on the best day, weather-wise, and just tell him to come and do it. It would need to be convenient for both parties, which may not always be the case.) Anyway, I thought of a way to do it with one coat only, taking my time during the next summer, and to me, it seemed that, after being done, there would not be any need to do it again. What I thought of was to paint it with bitumen paint, which (I think) would last for a very long time. (With luck, it may outlast me altogether.)
However, before embarking on this job, I should like to be sure about some things, and this is the reason for my posting. Here are some questions, and I would be grateful for considered answers to them.

1) The lower parts of the walls are coated with a green growth of some kind. It is not moss, such as grows on damp stones, but is certainly caused by damp conditions (where the shed stands, the ground is very damp, and trees grow over the shed and at the back and one side of it, thus keeping the air damp, and air circulation is inhibited to some degree). The growth washes off with Fairy liquid or similar liquid. If it were washed off as well as could be and allowed to dry, would bitumen paint stick to the wood, and even kill off any residue of this green film?
2) Is there any likelihood of the bitumen paint blistering and coming off in parts, when hot sunshine beats down on it? Or, to put the question another way: would bitumen paint be a durable finish that would withstand all of the elements? (If the paint blistered, it might then be necessary to scrape it all off, in order to apply ordinary preservative again. This could prove very difficult.) Therefore, it seems that to use bitumen paint would be to burn my boats, and put me in a worse position, afterwards, than seems to be the case now. This is why I am seeking the advice of others, to avoid making an expensive mistake.

With thanks to anyone that can offer informed advice,
A.W.

 

[Burnerman]

Personally I would doubt that bitumen would satisfactorily adhere to a pre treated timber surface.....have you considered a treatment that could be applied with a garden sprayer? Considerably less effort!
John

 

[Lucky Luke]

John, the back of the shed would be very difficult to use a sprayer on. There is only about 9 inches or so, for anyone to move there (there is a fence very close to the back, and the ground over the fence is not accessible, as it is closed at most times (it belongs to a public body). To make it worse, there is a water discharge pipe that comes from the shed at about 45 degrees, across the available space, so one has to crawl under it. By the way, the shed was treated with a single coat of Ronseal eighteen months ago or more ago, so perhaps it would not the affect bitumen paint's sticking qualities. All the same, thanks for your response!
A.W.

 

[Burnerman]

That is certainly awkward to access......however, some sprayers do have a 90 degree nozzle that could maybe allow a solution to run down the timbers from the top.
Either way you can't get a bitumen product in there either, so there's a bit of a plight.
Would it be possible for someone to hop over that fence when the access is, err, closed do you think to spray it for you?
I guess that spraying the shed timbers from the inside would at least penetrate the timber laps, do you think?
John

 

[Lucky Luke]

I know that you mean to be helpful, John, but there is no room at the back for any kind of tank from which to spray. I cannot get onto the top, as I used to, to attempt to spray downwards, and no, the fence around the publicly-owned space is to high for even a young person to do it safely. As regards a bitumen paint, I have carried a container of suitable size at the back (with difficulty, I must say), and applied preservative with a brush, so bitumen ought not to be any different. With regard to spraying from the inside, the walls are coated with plasterboard and packed with Rockwool, so this would not be possible. If I thought that bitumen paint would stay, I would first do a trial patch, to see how it bonds.

 

[Burnerman]

Hmmm my own sprayer has a bottle and 6' of tubing before the lance but I see what you mean.....if it was mine I think I'd consider lying on the roof and spraying downwards but it's not the best!
John (21 years your junior)

 

[JohnD]

does it have gutters and downpipe to prevent water running down the walls?

 

[Lucky Luke]

Yes, John D., it has gutters two sides and back — hence the discharge pipe. I really would like to know, for sure and from someone that knows, whether bitumen paint would stay for years and years.

 

[blightymam]

Bitumen paint is often used in fence posts to slow down the rotting.. and some makes of bitumen paints apparently say they can be applied to wood, but I don't think I'd like that idea on a whole shed. Does it expand etc with the wood and would it go on evenly or look really patchy... I wonder if the creasote substitute would be long lasting instead?

 

[Lucky Luke]

Bitumen paint is often used in fence posts to slow down the rotting.. and some makes of bitumen paints apparently say they can be applied to wood, but I don't think I'd like that idea on a whole shed. Does it expand etc with the wood and would it go on evenly or look really patchy... I wonder if the creasote substitute would be long lasting instead?

Perhaps it would not expand at the same rate as the wood, and would let in moisture. Thanks for your comments and information. I think the idea will have to be abandoned.
A.W.