Building attached garage up to boundary wall

Eddieice

Im looking to build an attached garage/workshop on the side on my house. I used to have a concrete garage but have since removed it due to no electricity and it was starting to fall apart. 
I have a large bit of space on the side of the house and could easily build a 2.6m by 8/9 m attached garage. The only issue is between myself and my neighbor due to the boundary wall as her driveway is at a higher level than mine. I was wondering if I would have to build inside of this line or I would be able to use the boundary wall as one of the walls of my garage/ workshop. This would result in only building one wall on the back with a doorway and window and building the garage entrance on the front with half the blockwork already done on the boundary wall I'd just be increasing the height. I was planning on running the roof front to back so no drainage was required over my neighbors land then.  I have attempted to scour the internet and not found anything that was very helpful. Hopefully someone may know something or assist is some ways.  I can provide pictures to help our if required. Thanks 

TELLIT01

As long as no part of your building overhangs the boundary line you could theoretically use the existing boundary wall and build up from it.  Bear in mind that the roof of the garage will inevitably overhang the wall, even if only for the depth of the fascia.  The question would be whether the foundation, and the wall, are strong enough to support the additional weight.

Alter_ego

Who owns the boundary wall? Who's land is it on?

Eddieice

i would be building from the rear of the property to 6m towards the front. ( Leaving enough space for more than 2 cars to park on the driveway. From what I'm aware it's my boundary wall. But the main thing is my neighbours driveway is at a higher level than mine but both houses are identical with the width of driveway so I won't be near her house wall and also from the location and heigh I'll be able to build too, I will not be blocking any sunlight.

Doozergirl

"From what I am aware" doesn't answer the question sufficiently.  

If it is your wall and the boundary is on her side of it, in theory you can build off it but you cannot have any element of that structure overhang that boundary.  

If it is a shared party wall, again, you can build up off it with a party wall agreement and all your structure coning off your side of that wall. 

If it is the neighbour's wall and the boundary is on the nearest side of the wall to you, then you will have to build away from it.  

I'm saying you can build off it but that doesn't actually look suitable and would probably develop damp very quickly.  The wall is better off being rebuilt with a proper vertical damp proof membrane and you'll end up needing a party wall agreement as your foundations are likely to be deeper than next door's.  

TheCyclingProgrammer

How can you be sure it's your boundary wall? The fact that the neighbour's fencing is attached to it would suggest to me that it could be their wall, or at least they might believe it to be their wall. 

I would err on the side of caution here - you don't want to get into a boundary dispute with your neighbour. Speaking as somebody who has been on their side of the fence, they may seriously object to what you're proposing and then you find yourself in an expensive battle to prove where the boundary is and who the wall belongs to. You can certainly ask - they might not care, but if they object think very carefully before getting into a battle.

Building right up to the boundary can feel very imposing. When our neighbours wanted to build up to the boundary I was very keen to keep our shared fence in place so their extension wall didn't feel as in our face.

Do the neighbours have room to extend in a similar fashion? If so you could sell it as being to their benefit by making your extension wall a party wall so they could build off it in future but if they don't then that's a non-starter.