Garden room height on sloped land

[Wils81]

I'm in the process of trying to build a garden room within PD and I'm going around in circles trying to get sufficient head here right. I've got one last hope othwrwise I'm going for PP.

The room will be 5m deep and 4.5m wide. The plan is to use 7x2 along the 4.5m span. First question would 6x2 doubled up be ok? it's a cold roof

If not and I go with the 7's, I would the run firrings perpendicular along the 5m span from front to back. All this would leave not enough head room.

My garden is on a slope. The back of the proposed build being 120mm higher than the front and it actually goes up to 170mm in the middle before dropping down to the front. My question is, if I take the height from the back of the build, can I run a firring front to back from 70mm down to zero and it not be included in the height. So the back of the build will be 2.5m and front 2.7 ish allowing for upstand.

I've attached a really bad drawing for clarity

Tia

 

[big-all]

the highest adjacent point is the datum point you measure from
so read this as the highest natural point it sits on as the point your 2.5mm is measured from
for the purposes off permitted development, it is counted as a a solid box with the maximum being assumed as applying across the whole box as in a wedge shape is assumed to be level with the highest point

 

[Wils81]

OK, so my phone plan would not be allowed. That's that then, I'll apply for PP. Thanks

 

[Wils81]

One last question if like in that drawing I've attached, I dig down the 120 mm difference from high to low point. Will the build height be taken from the highest remaining point or is this frowned upon by inspectors. Plan to build on concrete blocks and then a raft, so would pooling at the base be an issue

 

[big-all]

iff you mean dig down 120mm to give extra head room by sinking the shed then it will comply iff 2.5m from highest point to the side[adjacent point]
assuming thats what you where asking

 

[Wils81]

Thanks, yes, that's what I was getting at. Also that way the front of the shed wouldn't be quite a way off the ground. Just worried I'd create some kind of pond doing it like that

 

[big-all]

yes that is the problem
dig a test pit dig down say 400mm in the next few days and in dryish weather see if it fills --iff not it would suggest the water table is lower
make sure the cover sheds the water at least 600mm away preferably down slope iff possible

 

[thomp1983]

Your probably as easy to apply for pp and build something that you want instead of hobbling the project to stay within pd.

Aslong as your not building something massive your likely to receive pp and if you don't you can always fall back to pd.