Raindrops

 Midland railway water towers like ours had one major problem.  Water in the wrong place/s.

One source of unwanted water was condensation inside the tower - dealt with early in this Blog by spraying the underside of the tank with high expanding foam - totally successful.

Less successful have been efforts to stop rainwater, particularly when coming at the tank and tower horizontally, propelled by wind.  Rainwater cascades down the outer sides of the massive tank.  An ornate outer stone ledge shifts the water streams outwards a couple or feet or so to fall in large drops to the ground below - if the weather is calm.  If there is any wind, pressure builds on the windward side of the tower and the drops falling from the parapet get blown towards the tower walls and into the building through the slightest crack, propelled by the pressure difference on either side.   Notice the continuous horizontal crack between the ornately curved top stones and the huge square stone blocks below.  Those square blocks are there to support the huge iron girders which in turn support the iron tank and its contents.

This picture of the parapet's south east corner illustrates the situation

The gentle curves below the topmost ledge almost invite the rainwater to flow round them and on vertically downwards across the vertical stone face which is in the sunshine here.  If the wind is strong the drops travel horizontally towards the wall and on again downwards and into the wall.

Modern stonework of this type would have a drip-strip cut in the underside - but not ours.  For a water tower serving its original purpose this would not matter unduly of course.  Probably the worst example is inside the tower, not far from that south east corner:

Not a pretty sight.  Those rectangular stone blocks are massively heavy and straddle the entire thickness of the tops of the tower walls.  Clearly most of the water is cascading over the top of those stones but some appears to be creeping in below as well.  The problem is localised to four or five main points long the 156 feet total length of the tower's walls.

We have had some local success with gap filling where mortar joints have failed but it is tedious and not always effective - as here.  The remaining problem areas are at the corners of the tower - which catch the weather.  Gentle rain at ground level can be tempestuous at the top of the tower where wind inevitably is strengthened.

A local builder with a mind for such challenges had a close look at the problem last autumn and has since spoken to colleagues and heritage architects whose consensus is that we need to create drip strips right round the undersides of the horizontal overhang.  Not sunken channels but L section discreet strips.  We are in process of sourcing them against the following requirements:

- unobtrusive - maybe black or transparent but it would be in shadow so not critical

- severe weather resistant

- not subject to UV degradation

- lightweight for fixing at height

- cost effective - we need 50m of it in total

- if affordable we would use 100m and treat both of the lower stone right-angles

- L section plastic, stainless steel or copper depending on price and longevity

- Fixed by plugs and weatherproof screws at intervals to be decided

- sealant between drip strip and stone above

Watch this space.