Condensation around the base of the boiler flue on the roof

pieroabcd

Hi, 
Is it normal to have this condensation around the base of the boiler flue on the roof?
There's no leakage of any kind inside. 
Can it be a problem?
Thanks.

pieroabcd

With the boiler on I can see some dripping from the cowl, like a couple of drops per minute. 

GDB2222

Even with a condensing boiler there’s quite a bit of moisture in the exhaust gas. It’s cold, without much wind, so it’s condensing and the drops are falling on the roof. 

That’s my guess, but an expert will be along in a minute. 

martindow

How much of a fall is there on the roof?  It could be there is a slight dip in that area so a puddle forms and that it is rain rather than condensation leaving the mark.

pieroabcd

There must be a very slight inclination because when  it rains (even heavily) I rarely see puddle on the roof, and only at the sides of the lantern (a metre away from there). 
That picture was taken in the afternoon of a day that it hadn't rained. 

teaselMay

burning hydrocarbons produces water and carbon dioxide, which is what the water that you're seeing dripping will be, I'd guess it's been so still and dry but humid lately, here at least, that the effect of the drip is more obvious. Most important thing probably to make sure the roof is well sealed there but sounds as though it is.