Building a wall astride a boundary - impact on title deeds?

comeonletsgo

I have a query related to a planned rear extension on my terraced house.

Our neighbour has a side return extension and we would like to build our own extension adjacent to this. The complicating factor is that this existing extension wall is a few inches back from the boundary line, with the outer edge of the gutter running along the boundary line itself. So in order not to leave a gap, a new wall for our extension would need to run astride the boundary.

We have asked our neighbour if she would be happy for us to proceed in this way. However she has told us that she has been advised that building this new wall partly on her land would mean that she would need a new set of title deeds and it could impact getting a mortgage on the house.

My understanding is that this is not the case. The wall would be a jointly owned party wall and either side could in principle build off it (although less likely in practice as the existing extension already has its own wall). Building a new wall shouldn't affect the deeds in any way as the land ownership doesn't change.

However I've found it difficult to find something that sets out the situation clearly enough so we can have a shared understanding and come to an agreement on this. If we can't agree, we will need to build our extension more narrowly and leave a gap between the walls which is obviously not ideal. Does anyone have direct experience of this kind of situation, or any suggestions for guidance on this? 

TELLIT01

As the current wall is not built up to the boundary their mortgage lender would need to be informed of any intended encroachment beyond the existing boundary.  I doubt very much that they would be happy with the idea.  Your neighbour is right to be concerned and to speak to the mortgage lender, if there is a mortgage in place.  Irrespective of that they should speak to a solicitor to confirm that it won't require amendment to the deeds and/or create problems if they come to sell.