Garden office on ‘raised platform’

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Hi all;

I’m planning on building a garden office on a steep slope in our garden and all aspects comply with permitted development apart from one area I am unclear on....

my intention was to cut/fill level the existing slope and retain it with a full retaining wall.
The front elevation of the wall will be approx 550mm off the existing sloped ground level, the rear cut in approx 495mm.
The ground will be levelled to the top of the retaining wall and then the garden office built on top potentially with a thin decking step to the front I.e. walk up a set of steps on the front 550mm elevation onto decking (Below 300mm high) then into office.

By retaining this ground have I inadvertently created a ‘raised platform’ over 300mm which is not permitted or have I created a retaining wall with land behind which is under 1m high and permitted....

Any help/advice would be appreciated.

Pete
 

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The retaining wall is just part of the foundations.

The height of things is generally measured from the highest point of the natural ground around it. So for yours it's starting from -495.
Fun thought, you could probably have the roof a bit higher as you're starting below the natural ground level at one end.
 
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This will not be P.D. for two reasons:

1. You will be raising the ground at some point so that the raised platform will be > 30cm above the natural ground level at that point;

2. As you are excavating and building a retaining wall, the LPA will probably regard this part of the work as an 'engineering operation', which is also not P.D.
 
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"The height of things is generally measured from the highest point of the natural ground around it."


"the raised platform will be > 30cm above the natural ground level at that point;"


There's bit of a contradiction between those statements, or at least an ambiguity. The first states that the ground level is the highest point "around" it - the second says the ground level is the level "at that point."
As illustrated in this example, the difference is crucial where the ground level is considerably different at each end of the building. The datum has got to be the ground level either at the high end, or the low end, or be separately measured and applied at all points along. Which is it?
 
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There's something not quite right about your dimensions - see the blue notes.

Agree with Tony the deck would not comply, it could possibly be considered 'engineering' as per Tony.

So options are to lower the deck a bit and a big step up into the building or lower the deck & the building with a slightly taller retaining wall at the back. Or just apply for planning permission. Or if you're in the sticks then just get on with it. Or maybe have a side door access as your deck where you step out at the side could be higher as the ground is a higher there. There are probably ore options.

Why have a retaining wall at the front at all though? You could form a foundation pad at each front corner at the natural ground level and sit the building on some stilts or block piers or whatever, depending how the building is constructed. The retaining wall foundation at the rear could provided similar support at the rear.

bored.jpg
 
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Sorry for the delay:

Freddie - the dims on the drawing highlighted were different as the office is 3 x 3 and I was intending to put some decking at the front of the platform so you walk up to the ‘raised platform’ up some steps then on top of th platform have approx 800mm wide full width decking before stepping into the office. In reality it doesn’t need to have decking and could ultimately be right at the front of the platform, to almost give it an infinity look....
the only reason for a retaining wall was for neatness and essentially allowing me to form a pad. My intention was to install 9 foundation piers under the shed. We back onto the woods and I had thought about cracking on however one of the neighbours is a councillor and militant when anyone has any building materials delivered!‍♂️ Although she hates any new builds etc she doesn’t care her conifers are so tall they pretty make her house a hobbit hollow...


As I’ve read a retaining wall can be up to 2m or 1m within a highway and be permitted development and its hardly a feat of engineering being made out of sleepers with drainage behind, my view was anything over a days graft could be classed as engineering but the full retention excavation etc was only a day by the time I’d mixed up the concrete and wheelbarrowed up up my ski slope garden....

The whole situation seems to be so unclear I decided to pay for the privilege to the council for their ‘planning advice’ service as it’s pointless me cracking on based upon my viewpoint.... I’ll let you all know once the council reply (or are they still on furlough...)

pic of my current state of affairs - although I’ve stopped works for the moment.......
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I could always drop the level to 300mm on the retaining wall at the front, increase the wall height at the back then cut into the hillside - be a decent could of grab lorries away but probably cheaper than PP in all, plus my foundations wouldn’t need to be as deep as I’d hit the chalk a bit sooner..... ultimately though if I had the decking on top of the sleeper wall height this would again be over the 300mm height allowed ...!?!?
 
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been reading some older posts (of which I think a few of you offered advice on) although she had to dispute it to the end she won her case Some decking that was laid on a slope, although this is decking not a raised platform I think the same would apply..... albeit probably easier/cheaper/less stress to scoop out 10m3 or so (unbulked) of soil & drop the whole thing down...


QUOTE="Megar22, post: 4373068, member: 250504"]Hi Guys

It’s been a long time.

Just so you all know i appealed to the planning inspectorate and I WON. Got the decision today.

I was right all along. The council should measure from the highest point adjacent to the dwelling as the ground is sloping. As at that point the measurement does not exceed 0.30m the decking cannot be classed as a raised platform and therefore is a permitted development.

Thanks for your support!!![/QUOTE]
 
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As illustrated in this example, the difference is crucial where the ground level is considerably different at each end of the building. The datum has got to be the ground level either at the high end, or the low end, or be separately measured and applied at all points along. Which is it?

The usual interpretation is that 'height' is measured from the highest point of contact of the natural ground level with the structure. 'Natural ground level' is inserted to ensure that builders don't artificially build up the ground.

There are many appeal decisions on the Planning Jungle site where Planning Inspectors have determined that this is the correct interpretation of 'height'. However, there are a small number of cases where inspectors have determined that the height can be measured at any point along the structure, but these decisions seem to be outliers.

In the OP's case, building up the ground to more than 30cm above the natural ground level would render the project not P.D. Digging the far end further into the hillside to lower the platform might seem the obvious work-round, but a pedantic planning officer might then class the excavation as engineering works and therefore not P.D.

(Not trying to pour cold water on the project - merely being devil's advocate - as some jobsworths at the council will go to any lengths to prove a point, get a fee in, and enjoy their little power trip).
 
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Tony1851 - you are completely right as all the blogs/posts I’ve read all seem to be ‘reasonably’ straight cut but somehow always in dispute with the council, I’m sure I even read one where a planning officer said its PD etc BUT advised the applicant to go for LDC regardless as he couldn’t guarantee it lol. I spoke to several garden office installation companies who couldn’t even give a straight yes or no so it does really suggest that each council/planner can read the ‘guidelines’ in their own individual way, I feel confident but I honestly couldn’t be bothered with the arse factor of dealing with the council/planners correspondence etc for the next 8 months, I can see the case from both sides so I’ll try to be patient for once and await the planners advice I’ve paid for..... amazingly he emailed me within 24 hrs of the application to tell me he can’t reply for a month..... at least the council are trying to manage expectations for once! I will keep all informed ‘when’ I finally get an answer from them
 

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