I am having my roof replaced which adjoins my neighbours, whats the best method of ensuring there is a seal with the existing tiles next door?

Very often each roof in a row of terraced or semi-detached houses will need to be replaced individually; therefore the joint between the old and new tiling or slating between two houses must be weathered. 

Sometimes this is done by simply mortaring a row of tiles or ridge tiles over the joint. Unfortunately, this can often lead to leaks and is not to be recommended. 

A far better solution is to incorporate a ‘bonding’ or ‘jointing’ gutter. This can be formed from lead, or alternatively, there are a number of proprietary systems available. A bonding gutter not only provides an effective means to weather the junction, but it also gives a neat appearance, with old and new materials finishing closely together and the gutter being almost completely hidden.