Houses rebuilt after the 1774 fire have had over two centuries to settle. Their roofs are rarely straight, and trying to make them so does more harm than good. Walls lean, wall plates bow and rafters twist a little, and the covering follows all of it.
Q2.1When is a sag a problem?
When it is new, or getting worse. A sag that has been there for decades is usually stable. Fresh cracks in the plaster below, doors that stick and a ridge that has dropped since last year are signs of movement that needs a structural opinion. From the loft we examine rafters, purlins and wall plates, photographing each as we go. A purlin is the horizontal timber that helps carry the rafters between the ridge and the wall.
Q2.2Can the covering be lifted and re-laid?
Often. On an old roof we prefer to take a slope off carefully, sort what can be reused, repair or add timbers and put the covering back in order. Each slate, tile or stone goes back in the same part of the slope where possible. That keeps the look and character of the building. Where tiles are missing or damaged, matching replacements are sourced rather than mixing in something that stands out for years.
Q2.3Will the weight of the covering change?
It can. A covering more than 15 per cent heavier needs approval under Approved Document A, and Wiltshire Council's building control team or a registered building control approver deals with that. We work out the load before we recommend a material, and put the result in the quote.
If you think a roof has moved, do not wait for a storm. Photographs of the ceilings and the ridge line, taken from the same spot each month, give us a useful record, and they help you see whether a crack is growing or has simply stayed put.