Fly problem Diagnosed - the Answer is Below-Decks

 Several earlier posts have dealt with the problem of tiny flies which infest the roof room each winter.   I had been calling them cluster flies - wrongly.   Today, Harry, a fly specialist from Rentokil came to have a look-see.  Straight away he was able to identify FILTER FLIES as the culprits.  100%.  They are harmless but they are an invasive seasonal nuisance.

They (Psychodidae if we're being posh) are minute (about 1/8 inch long) and have a life cycle of just three days.  They lay their eggs in standing water which contains rotting or other such matter in it.  Just the sort of thing that would accumulate on the fibreglass roof of a former railway water tower!  There, they breed like, er, flies.   In summer they fly off and do whatever flies do.  In winter they seek refuge in any nook or cranney they can find.  That could be the inside of a three pin electrical plug, they are that small.

Our room inside the tank is heaven on earth for them.  They breed and hatch in the puddling water outside then come indoors for shelter, via even the tiniest crack.  In winter they do their entire life cycle indoors and repeat over and over again, multiplying in numbers each time.

Beautiful, moth-like things but not in these sorts of numbers, thank you:

The solution is to clean out and ry out the breeding habitat below the outside decking on the south, west and north sides.   Rentokil will then use its industrial grade insecticide to kill off the colony, eggs and all.  To do that effectively though they need good access to underneath the decks so I am creating that for them - and for me to be able to have easy access to pressure-wash and spray below, ongoing.

The western walkway needs serious attention, seen here.  The central boards are being lifted, cleaned and deck-oiled before being upturned and put back using stainless steel screws for easy removal and for access.  The four boards running the entire length of the tank will be removed and treated, creating access to all areas below all decks.  At the far end you can see prepared and oiled boards drying off in the sun, looking good as new.

The sub framework is in very good order.  It is in treated timber and I well remember soaking the feet of each upright in good-old creosote, which has done its job well.  Each of those rests on a galvanised steel plate to spread the load onto the fibreglass roof below.

Keeps me fit and out of mischief.