Will the neighbours’ extension limit plans to extend our home?

We are looking at buying a semi-detached house and extending over the garage to the boundary line with our potential neighbour on the first floor.

However, on closer inspection the neighbour has done a similar over-garage-extension but has set it back 50cm from the boundary line. There is an opaque window on this wall directly facing our potential new home at first-floor level (bedroom level) We looked at the planning drawings and planning was granted for this window.

I have two questions for you:

1. Will their extension and window prevent us from gaining planning permission for our over-garage-extension? If yes, on what grounds?
2. If we are also required to set our extension back from their boundary line, will it be difficult to build and maintain our wall? Say we are asked to step ours back 50cm also, that would only leave a 1m gap between the two houses.

Noel Larkin replies: It is difficult to fully answer your question without physically viewing the situation. You mention that the next-door property has been extended over the garage and that you intend to do likewise. You state that next door has set back their extension by 500mm from the boundary and that if you do the same, a 1000mm gap will result.

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I assume that there is no gap between the adjoining garages and that a narrow flat roof now exists at first-floor line on the neighbouring property and a similar narrow flat roof will exist on the subject property. I suspect that the 500mm setback was introduced to accommodate the window you mention on the neighbouring property as it is unlikely that a window would be permitted on the boundary line.

In this case the provision of an extension on or near the boundary line will cause difficulty in terms of maintaining day lighting to the neighbouring property. Although your neighbour may well “rage against the dying of the light” there is no legal “right to light” in this jurisdiction. A right or easement can be granted to a neighbour however. You should therefore check if any such easement exists before buying the property. If no such easement has been granted then there is no legal reason to stop you building an extension that will limit daylighting to your neighbours’ window.

Some local authorities do require a setback or break between adjacent houses so that a 1000mm gap is maintained between properties so as to prevent houses intended as being detached from becoming a terrace. Apart from being visually incongruous there can be issues created in terms of thermal movement and expansion on the resulting terrace.

Constructing right up or close to the boundary line can create issues in terms of buildability. You will need access to next door to place scaffolding to allow construction of the side wall and to enable rendering. You will also need access for maintenance, cleaning of gutters, painting etc. You will need your neighbours’ consent to access this area for initial construction but also when crossing the boundary line to carry out maintenance. Common sense should prevail. However, when a non-cooperative neighbour is encountered, a works order, introduced by the Land and Conveyancing Law Reform Act, 2009, can be sought in the District Court.

Have the situation reviewed by your surveyor as part of their pre-purchase inspection. Most building surveyors are happy to comment on future plans and they can help identify if there are any obstacles in the way of extending the property. It would do no harm to meet the neighbour and discuss your intentions. A brief discussion on the matter might be enough to alert you to any pitfalls which might lie ahead.

• Noel Larkin is a chartered building surveyor and a member of the Society of Chartered Surveyors Ireland, scsi.ie