Wood Rot on joist and bearers

[co_ol]

I have a timber deck about 14 years old and is in very bad condition. I started looking in replacing the decking but realized that there is wood root on the surface of the joists.
I also have large cracks from the nails. I have used a belt sander to sand of the top surface of the joist and the timber underneath looks still solid.
My questions is, what would be the best process in treating the timber for the rot and what would be the best product or procedure to preserve the timber?
What would be the best product to fill the cracks and gaps in the timber?
I also have some poles affected by water sitting on the surface that show some rot. Is it safe to seal the whole stump with a bitumen type sealant from further rot and what product best to use?
Replacing the joist would be way to expensive for me since the whole decking area is around a 100 square meters.
I appreciate any comment or advice.

[journeyman Mick]

Fungal decay is a lot like cancer, you need to cut it all out to stop it from reoccurring. I would replace any of the rotten stumps. It's fairly pointless filling the cracks with anything, but you could paint them with creosote to prevent rot (if you can still get it). Lay strips of dampcourse on top of the joists before laying your decking, this will shed the bulk of the water and protect the joists. Apparently you can now get strips of plastic dampcourse cut to width specifically for joists and a slightly wider one for bearers. We just used to cut normal dampcourse to width with snips, If you're interested I can do you some 90 x 19 decking for $4.90 a lineal metre. Go see the blokes at Cairns Coatings for more information on coatings and preservative treatments, they'll point you in the right direction.

Mick