The first post in this series was about walls. Here are two pictures of stone walls in the neighbourhood, one well repaired, the other not so well repaired.
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| This wall has some sandstone (Heavitree stone) and therefore has been repaired with lime mortar, which is porous. The mortar supports some vegetation |
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| The wall has blocks of sandstone and has been repaired with a hard mortar (almost concrete) which is not porous. With weathering (especially water) the stone has been worn away and the hard material left proud of the surface. In turn this traps the water and further erodes the stone. This mortar is devoid of vegetation. |
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