Hot Glue Gun for Pointing

Our new lounge in the extension will have one main wall of 1876-built sandstone - the one-time external wall of the top of the tower.  Because of its function - to support a massive weight of water in the sky- the tower's walls, beside being massively thick, have the unusual feature of very narrowly pointed gaps between the courses of sandstone.   That is fine but it makes re-pointing, should it ever be necessary, almost impossible in such narrow gaps.   In fact, the lime mortar is in amazingly good order after 140+ years of exposure to the elements.

The tower walls are rubble-filled hollow and ventilated through cast iron air vents.  These keep the walls dry but also mean that when the wind blows there is positive pressure inside the walls which will leak out through any gaps in the pointing.   This is fine - indeed to be encouraged normally - but unwelcome when you are building-on an air-tight extension with heat-recovery ventilation which depends on an air-tight structure if it is to be efficient.

The retention of the former external wall as a feature of the new lounge is deliberate and should be a stunning visual feature but it needs to be air-tight.   Close inspection of the pointing revealed small but numerous holes in the pointing which needed to be filled.  But how?  Re-pointing was impossible with the very narrow layers of very hard lime mortar.   Patch-pointing could be visible to an unwanted extent.  I thought long and hard about this problem.  As a veteran of many things, including restoring several old buildings I eventually hit upon the solution.   Why not use hot glue from a glue gun?  Transparent, easy to apply, should be almost invisible from anything other than the closest scrutiny.   Most importantly, effective.

Well, today was the day.

Here is a picture of the sorts of holes that required filling

click to enlarge

Below are similar holes that have had hot glue fillings:

Obvious on close inspection but overall, invisible.

The top picture shows the remains of ivy roots, which once populated large portions of the tower's walls - and possibly accounted for some of the holes too.   I shall try to find a picture of this east wall with ivy growing on it.

Didn't have to look far - they are on this very Blog back in early 2011:

The lounge is built over the section of wall from the nearest corner of the tower to approximately the point where the ivy starts.  The dark rectangle at the start of the ivy is one of the iron ventilation grills on this east face of the tower.  It is now part of the lounge wall.

Below is that east face when cleared of ivy: