Sloping Garden / Excavated Garden Room

[MargoSmith]

Hi, I wonder if anyone can give me some inputs on an idea I have for my garden.

I have a house with a smallish garden, and the garden is quite sloped. Neighbours have built decking to make their gardens more usable, however I would like to create a garden room.

To do this, I envisage having to excavate a load of ground and then build a retaining wall, and then build the garden room. I think the room can be 4x3mtrs

The house is next to a road and I think the garden boundary is around 1mtrs from the road (it's a country lane).

I presume I would need to build retaining walls and then put in a concrete base and then build the building. I want to be able to walk on the roof, because the roof of the building would be level with the ground on my patio.

I have some photos and a diagram that explains the idea.

Would you guys say this is possible without breaking the bank?


Concept

View of sloping garden

Patio Area

Road next to house

 

[MargoSmith]

Would the "45 degree rule" apply to the ground near the road?

 

[MargoSmith]

And the view from the bottom upwards.

 

[George_engineer]

This is none trivial but could be a good project

- in front of the principal elevation so may need planning
- retaining wall isn't supporting the the road so shouldn't need highways approval, but looks to be supporting the the house and is pretty tall so will need building regulations approval
- building the retaining wall is always tricky if you don't have space to batter back the excavation. May need sheet piling or another temporary works scheme
- detailing for a walk on roof is a bit more involved than a normal shed roof
- the 45 degree question - is that for putting in foundations? Short answer is yes. Can't undermine roads

So could be possible, subject to planning but I think you will need professional help for the design and detailing.

 

[Notch7]

Would you guys say this is possible without breaking the bank?

The groundwork’s to dig out and do the retaining wall could cost £20k before you start the garden building.



building regs would require balustrading to protect against falling

 

[MargoSmith]

The groundwork’s to dig out and do the retaining wall could cost £20k before you start the garden building.



building regs would require balustrading to protect against falling

20k to dig a hole? Seriously??

I was gonna hire a digger and do it myself.

Why so expensive?

 

[MargoSmith]

This is none trivial but could be a good project

- in front of the principal elevation so may need planning
- retaining wall isn't supporting the the road so shouldn't need highways approval, but looks to be supporting the the house and is pretty tall so will need building regulations approval
- building the retaining wall is always tricky if you don't have space to batter back the excavation. May need sheet piling or another temporary works scheme
- detailing for a walk on roof is a bit more involved than a normal shed roof
- the 45 degree question - is that for putting in foundations? Short answer is yes. Can't undermine roads

So could be possible, subject to planning but I think you will need professional help for the design and detailing.

The back of the office would be about 1m from the road if I placed it on the left side of the garden (looking upwards) and I think about 5m from road if on the right side. However the views on the left would be much nicer.
I think its the road thats the ticking point. Who do I need to talk to in order to get a proper idea of regulations on that, or where can I look to find out what the regs say, any idea?

What type of contractor would you recommend for this type of job? Just a general builder or some specialist who does ground work?

 

[kp00110]

I'd go for a civils and groundworks contractor for the dig, drainage and retaining wall structure, and a general builder or garden room specialist etc for the actual build of the garden room. I'm sure you can get someone to do it all but they would probably sub out anyway or cut corners with the things they dont know about

 

[MargoSmith]

I'd go for a civils and groundworks contractor for the dig, drainage and retaining wall structure, and a general builder or garden room specialist etc for the actual build of the garden room. I'm sure you can get someone to do it all but they would probably sub out anyway or cut corners with the things they dont know about

Thanks, that makes sense.

So I should probably start there and get some idea of costs.

I think it can all be concreted and then I will use something like monocapa (monocouche) to render it the visible areas, which I can do myself.

So for the roof, would I be better to use steel beams and some form of boarding? Needs to be strong enough for a bbq etc...

 

[freddiemercurystwin]

I'd think £20k for the wall is a good starting point and maybe the same again for the building depending on the type of building + SE fees + the Planning and Building Regs fees, all subject to planning of course, as for the roof structure that should be the least of your concerns.

 

[MargoSmith]

I'd think £20k for the wall is a good starting point and maybe the same again for the building depending on the type of building + SE fees + the Planning and Building Regs fees, all subject to planning of course, as for the roof structure that should be the least of your concerns.

20k seems a lot!! Was looking at something like a steel frame building, put boards on it and render it, paint it white. About 3k for the frame with these guys below.

Steel Frame Garden Building (2.6M X 3.8M) | Buy Online at Permaroof UK

This beautiful steel frame garden building provides vital additional living space for a wide range of uses. Suitable for DIY, buy online with fast delivery.

www.permaroofstore.co.uk

I can build that myself I guess and should be plenty strong enough for standing on the roof.

 

[freddiemercurystwin]

That's completely unsuitable, you're not building a roof, you're building a waterproof floor and with a balcony attached to the edge.

 

[MargoSmith]

That's completely unsuitable, you're not building a roof, you're building a waterproof floor and with a balcony attached to the edge.

Would you mind elaborating a bit why its unsuitable?

 

[freddiemercurystwin]

Because that frame isn't designed to cope with using the roof as a floor, the floor loadings required for a floor are greater than a roof.

 

[MargoSmith]

Because that frame isn't designed to cope with using the roof as a floor, the floor loadings required for a floor are greater than a roof.

Ok, I understand, makes sense, but if the frame is of the appropriate gauge to take the calculated "live load", would this construction method not be suitable?

My understanding is that these steel systems are actually stronger than wood?