Recoating shed roof with bitumen paint?

I have a shed covered with tongue-and-groove cladding, which I've repainted on the outside since it was built.
The roof is the same material but covered with roofing felt. I'd like to make the roof last a long time and I happen to have some bitumen paint lying around --- would putting a few coats of this on the roofing felt every few years be a good way of extending its durability?
Thanks, Adam
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Yes, though the paint doesn't last too well. Keep the brush/roller in a near-empty tin of bit paint for next year. Or wrap it in plastic, and stick it in the paint a few days before you use it next. It will stiffen up a bit, but soften in while if immersed in the paint. Not worth the mess to wash it out.
The paint comes off hands etc very well with baby oil, or oil-soaked baby bum wipes. Skin-friendlier and less smelly than diesel...
Thomas Prufer
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Do you mean a tin of it, once opened, doesn't last long even stored properly? In that case, I'd better look in the old tin before I get set up to use it....

I find disposable rubber gloves are worthwhile for painting (even with normal paint).
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Oh no, the tin lasts a long time. And I think any old solvent would do to thin the stuff if it had dried up a bit. Let it get good and warm give it a good stir, and off you go.
I meant that the bitumen paints I've used all have weathered off fairly quickly. There's a few that supposedly last a lot longer: some sort of water-soluble acrylic roof paint, or two-pack epoxy stuff. One look at the label: coverage rates and the price tag mean that I can either put up a new roof for the money, or keep the money and slap paint on every two years or so.
Thomas Prufer
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Thanks for the info. I'll look into the butyl pond liner, or else "reinforce" the bitumen paint with sand.
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Adam Funk wrote:

If you want it to last a long tiime buy a Butyl pond liner and use that as a roofing membrane, it'll go for 30 years or more !! I have two sheds/utillity room done like this with ply underneath, works a treat !! got mine from www.pondlinersdirect.co.uk
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Ack. Felt's not all that great, as UV breaks down the bitumen eventually.
Neighbor tossed a thick layer of sand on his ancient felt roof when he painted his with bituminous paint. It has extended the life considerably -- the layer of sand seems to protect the paint. His roof is fairly steep, though, I'd worry that stuff would stick to the sand layer if it were flattish -- though moss should protect form UV as well?
Thomas Prufer
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This one's not steep at all, although there's nothing growing on it yet (a few years after installation).
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I'll look into that; thanks.
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Adam Funk wrote:

No. The felt fails because the felt itself goes brittle and cracks, not through the failure of any surface waterproofing layer that could be restored by painting it.
The main culprit here is UV radiation, so anything you do at construction time that reduces this can be useful. Sand coated felt, or even painting it white, will help. Bitumen roofing felt already has plenty of bitumen in it though, so painting more on doesn't add anything.
A coat of bitumen paint on the timber underneath is useful though. This helps to protect the wood from any moisture that does find its way under.
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So the only real solution is to replace the exposed felt occasionally...

...and do this. Or use the butyl rubber pond liner, as someone else has suggested.
I take it roofing felt *in a roof* lasts a long time because the slates protect it from the UV rays?
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