The Mad Surveyor

I was asked to look at an old Cotswold stone barn roof this week.

It was built originally around 1860 (the owner believed) and was in need of some TLC, quite a lot actually. Now back then these roofs were constructed by laying stone tiles on mortar beds across supporting laths, a bit like laying bricks since the stones clearly did not have nips to grip laths. Then they would finish off the inside by pointing between the laths with a mixture of horse hair and plaster mortar, the horse hair helping to secure and strengthen the bonding. I suppose in its day not a bad solution and probably looked quite neat by the time a skilled tradesman had finished, clearly not a job for a novice.

The condition I saw it in, however, was far from neat. Most of the pointing was perished, stone tiles had slipped or were missing, water had clearly been penetrating the roof for quite some time and internal pointing between laths was mostly hanging off. A mess really.

Now the reason I was there was to assess if this roof could be rescued using polyurethane foam. Sadly the answer was no. The foam to act as a bonding agent to prevent tile slippage most clearly be attached to the underside of the tile, in this case this would have been well neigh impossible because of the decayed pointing and mortar beds being in the way and there being no way this could be effectively removed without moving the tiles from the roof. Also, the fact that the roof needed major stone replacements, a lot were cracked or missing completely, meant we had a very leaky roof unsuitable for foam application without a lot of remedial work, a very lot! My view was that the roof had been left too long in a bad state of repair and had decayed to the point were only a re-roof would do justice to the job. Now, the customer was reluctant to do a re-roof since he had worked out that he would need the best part of 20 tons of stone tiles at £2000 per ton! And the fact that he has estimated that he would recover no more than 2 tons from the existing roof due to the overall bad condition. He was also in a conservation area which meant that he did not have an option about the roofing material; it had to be Cotswold stone period.

I left giving a price estimate but I think the job is down to affordability, it clearly is going to be an expensive re-roof due to the materials and not one that can be solved using polyurethane spray foam.