If only doing part of the work means that the bit you build will look different in anyway from how it was shown on the approved drawings you will need to speak to the Council (eg a new wall having to be built where the two would have joined, or a change in the roof shape etc). They may allow it as a non material amendment, which can often be dealt with just by letter.
It was shown as L in the original application. Not as separate extensions. Though I am sure neighbours and planning officer would be happy if we do only rear and not side extension, so almost sure if we apply new, we will get approval. Just trying to avoid a new application to save time and cost. Can we say side would be phase two and may be never do it in future.
If they hadn't been joined, you could do as two phases, but if they were shown joined, then the extension will not be built as approved, and therefore would strictly be unauthorised. As I said, speak to the planning officer who dealt with the application and see whether they would just accept new plans with a letter to 'rubber stamp' or whether they will require a new application.
There's no rule that you have to finish the whole thing in one go. You can just do part of it and do the rest later on if you want. Like pp said though, you need to actually be able to do part of it how it's shown in the plans, so if you'd have to change the roof shape or whatever then it would need a new permission.
The side extension from outside elevations looks like it is attached to the side, so fairly independent of the main rear and firstfloor extension. From inside, in floor plan we have shown as we removed the side wall and incorporated the side extension into the rear extension and main house.
When people apply for say single storey side, single storey rear and loft extension together and then do only rear and loft (and not do the side), do they need to apply for new permission? In floor plan they might or might not have merged the side extension. I thought planners were only concerned about outside look. I really wish now we should have put seperate applications for each side.
If the additions are unconnected and can be built without changing the external appearance in any way from the approved plans you will be fine. The internal layout is not important unless it means that you will be changing the position of external doors or windows for example. If the rear addition can be built on its own without any changes from the approved drawings then you will not need a new application.
If you want to post an extract of the floor plan showing the two extensions I can have a quick look.
We would have to change external doors to windows. So there would be a change to rear elevation. I have seen people putting retrospective amended plans for door/window changes so that might be a possibility. I have added image of plan. Blue bits are what we dont want to build.
The appearance (and size) of the rear extension is changing so it will not be covered by the existing planning permission. You will need to speak to your planning officer to see whether they will accept just revised plans and letter to cover it or whether they will require the more formal Non Material Amendment process which is like a mini-application.
I can't really work out where your existing wall is, but it's possible you could put in the foundations for all of it, then just do the bit you can afford - some neighbours at my old house did this, dug out and put in all the foundations, built the side kitchen extension, and covered the back foundations that they didn't build with patio. As they'd started the rear build it was actually about 9 or 10 years later when they had 3 teenagers & started needing the extra room they finished building the rear extension.
We did exactly this. Applied for planning permission for side and rear double storey extension. Got planning permission, all fine. Then got quotes back & realised we couldn't afford it. Decided to lose the side extension and just do rear extension.
Spoke to Council, they said we could change the plans as a non-material amendment. You do have to go back to the Council if you are changing where doors and windows will go for example.
So made the non-material amendment application (with amended drawings etc) which was about £30 I seem to recall. All fine.
Then at the last hurdle, it apparently went to committee and it was deemed in fact not to be a non-material amendment (NMA), we had to make a whole new application. They did say however that they'd refund the £30 when we paid the new application fee of £200 or thereabouts as they realised they'd messed us about.
They said that NMAs are a change if door position / window / a few cm here or there. If you're fundamentally changing the structure of the extension, then it needs a new planning application.