Decking on sloping ground

[MrSlope]

Hello -

My house is built on higher ground than my neighbour's. There's currently a

1 metre height difference between my garden and my neighbours, retained only by a wooden fence which is beginning to fail. It looks something like this: 'd like to avoid the cost, possible damage to trees, and disruption of having a block retaining wall built, and a structural engineer has suggested excavating the part of my garden next to the fence, to restore something similar to the original slope, and then putting in decking over the resulting sloping ground.

Does this sound like a good idea? What sort of slope angle might the engineer suggest, given that the soil is clay (this will determine the area of decking) ? Is this likely to be cheaper than a block retaining wall, given that less excavation is required? What might the cost of the decking per square metre be? Would planning permission be required?

[MrSlope]

This is a better diagram, showing some mature trees in the neighbour's garden that might interfere with the footings of a retaining wall:

[Bruce]

Have you consulted your neighbours?

How happy do you think your neighbours would be with decking on your property that would be 1 metre higher than their garden and ran to the shared boundary?

If I was your neighbour I don't think I would be at all happy with what you are proposing. I think I would probably be *livid* if you went ahead and did it without discussing it with me first.

I'm not surprised you have posted anonymously. :-(

[MrSlope]

Hello -

The my garden is currently 1 metre higher than theirs, so overlooking is hard to avoid. One of the reasons I want to avoid damage to the trees is that they provide some privacy, so I seem to have limitted options.

[Harry Bloomfield]

It happens that MrSlope formulated :

I'm not suggesting this as a solution, but might some steel piling (instead of a wall) solve the problem? This assumes there are no pipes, cables or drains in the area of interest.

[MrSlope]

I don't think there are any pipes, etc. in the area, but there are probably tree roots. Access to the site with anything bigger than a wheelbarrow is difficult, so piling may not be possible if it involves a big machine.

[Tim Watts]

Bruce wibbled on Sunday 25 April 2010 09:28

He's suggesting excavating the ground and installing the decking at the original height of the ground. Why should there be any problem with maintaining the status quo?

[Bruce]

You appear to be limiting your options even further, and maximising the potential for an upsetting (and completely unnecessary) dispute, by not discussing with your neighbours your ideas for this *shared boundary*.

[Tim Watts]

MrSlope wibbled on Sunday 25 April 2010 08:31

45 degrees. I have slopes like that in my garden on clay. I've got a bank at about 2' high with a slope of about 30 degrees off vertical that is stable, so you can get away with more.

Check the "planning portal" but I doubt it as your decking would not be above the original ground level - but you should read it yourself.

[Bruce]

You've missed the point. The original ground level was at the base of the fence. The ground level has subsequently been raised by about a metre by the OP which has caused the fence to fail - principally because it is just a boundary fence and not a retaining wall.

The worst aspect is that the OP does not appear to be talking to the neighbour - something he should be doing rather than posting here.

[Harry Bloomfield]

Bruce brought next idea :

The OP does not indicate that - my assumption was that the builder had perhaps adjusted he level and caused the problem.

[Tim Watts]

Bruce wibbled on Sunday 25 April 2010 09:53

Hi Bruce,

I'm not sure I missed the point - I've been through all of the OP's posts and I couldn't find any indication *he* raised the ground. It could have been like that a decade - he didn't say how substantial the fence was.

Although I'm not sure how to read this: "...to restore something similar to the original slope..."

OP - can you clarify please.

Generally a good idea, but if he can't stand his neighbour, he may not wish to and doesn't have to providing he stays within the law. It happens.

[MrSlope]

One of the previous owners of the house raised the level of the garden, which is what is causing the fence to lean over. I would rather not completely revert to the original slope of the garden, because that would make the garden less useful and maybe devalue the property. I wouldn't mind having the proposed decking slightly lower than the garden currently is, maybe by 30cm. I have briefly discussed this with the neighbours, and they are quite relaxed at present, but I'd like to know what is technically possible before bothering them further.

[The Medway Handyman]

If any part of the deck is more than 30cm above the ground you need planning permission., no question.

Cost of (flat) decking is between £50 & £80 a square metre. Raised decks & difficult access will add to the cost.

[MrSlope]

SNIPPED

Hello -

What I'd effectively be doing is digging a 1 metre hole, and then putting decking across the top. I wouldn't want any part of the decking above the level of the ground as it is today, and would probably want it slightly lower. Do you think planning permission be required in this case?

Thanks.

[The Medway Handyman]

Dunno to be honest, more info here

click the link at the bottom of the page.

[Tim Watts]

MrSlope wibbled on Sunday 25 April 2010 10:12

OK - how long has it been like that? May have a bearing on planning laws should your neighbour get weird in the future...

OK - there is another option: Build a retaining wall out of railway sleepers (new ones, pressure treated).

You will need to set sleepers on end, or concrete posts, into the ground about every 4 feet, well concreted in below the lowest ground level (ie your neighbour's ground level). So you will have some holes to dig, but not a trench.

Then lay the sleepers *on edge* between the posts and your soil bank (you will have to obviously clear back enough soil to do this).

Overlap the joints like brickwork and screw each sleeper into the one below using 240/250mm landscaping screws, predrilling the top sleeper and further drilling a head clearance hole part way through so that sufficient length of the screw goes into the lower sleeper. Screw ever 300mm or so.

A mate built a retaining wall like this which holds back about 1m of soil so it is a proven method. Should last a fairly long time.

I expect you could do the same thing with concrete "planks" between concrete posts. The main advantage is that you only need to sink posts rather than trench a full strip foundation so it's easier to manage tree roots.

[Tim Watts]

The Medway Handyman wibbled on Sunday 25 April 2010 10:41

Which ground level is the question though...

It's getting dicey, legally - which is why I asked how long the ground had been like that. If the "new" ground level has been there long enough, the OP's decking is merely matching that ground level.

[fred]

In article , Tim Watts writes

I think the retaining wall ideas have already been covered. Unless I am mistaken, this is the o/p from the broken "Building a retaining wall next to trees - will it harm them ?" / "Building a retaining wall close to trees" thread combo and helpful suggestions have been made.

As to planning permission for a deck, if the second drawing provided is accurate, it suggests about 2m of the deck would be more than 30cm above the level of the bank meaning planning permission would be required.

[The Natural Philosopher]

The Medway Handyman wrote: .

Which bit of the ground would that be then. The bit where you piled a meter high pile of earth?