manhole cover/pipe positions

[jb1468]

Sorry if this is in wrong section - unsure where to put it.

I am preparing the ground for a deck area in my back garden and have exposed a manhole cover that I never knew was there (someone at some point had covered in about 8 inches of soil when levelling an area of the garden) My problem is I need to place a post in that area to support the decking and am concerned about accidentally causing damage to whatever pipes are under or around it. Without going into fine detail I really need to put a post in that area and cannot just avoid it so a solution may be required.

The manhole cover itself is surrounded by or set into concrete about 45 inches by 24 inches. I assume its sewage/waste water but not really sure if it can be for something else. I live on a slope in the middle of 5 terraced houses (2 higher above me and 2 lower below) and I assume that this drainage runs at least for these 5 houses. The property was built in the 60’s. Questions –

1. How deep can I assume the pipes are below ground or can I assume anything.
2. Does anyone know the circumference size of the pipes underground as I may be able to move enough sideways for the post to avoid it if it is not deep enough to avoid. 3. If I was to move sideways is it safe enough to assume that these pipes run straight down the hill/garden from the manhole cover to serve the houses above/below and not sideways or any other angle for example to serve houses backing on to these 5.
4. What are the underground pipes made of and if careful digging down how easy are they to damage/split if I calculate wrong or they are places at a height/angle that is unexpected.

Thanks in advance – I know little about outside drainage/waste

 

[mointainwalker]

But if you lift the cover ( with the tip of a pick ? ) this will answer most of your questions: i.e.

1) Depth of pipes
2) Material of pipes
3) Which way pipes run.

 

[freddiemercurystwin]

But if you lift the cover ( with the tip of a pick ? ) this will answer most of your questions: i.e.

1) Depth of pipes
2) Material of pipes
3) Which way pipes run.

I thought it was a trick question!

 

[jb1468]

But if you lift the cover ( with the tip of a pick ? ) this will answer most of your questions: i.e.

1) Depth of pipes
2) Material of pipes
3) Which way pipes run.

Sorry I did not make the positioning of the manhole cover clear enough to avoid you wondering why i didn't so as you advised. There is only about 10-20% of it exposed in my garden. The vast majority is in my neighbours garden. They must have leveled there garden at one point resulting in about 3 feet of soil/lawn on top of the majority of the manhole access not to mention the heavy fence etc. I doubt if i tried I could lift more than an inch and risk disrupting their garden etc in attempting to do so.

I asked as i wondered whether there were regulations that might have been known by someone where it must be down a certain depth etc ......

Thanks for your response - I guess the obvious must be asked first.

 

[mointainwalker]

Current regulations call for just about everything to be 750 - 1,000 mm deep and I doubt it was much different in the 60's .

That apart however, must you bury this post ? If there are enough others buried, could you not simply sit this one on a flagstone, maybe flush with the surface of the soil for aesthetic reasons ?


Have never laid decking, so apologies to anyone if I have just contravened some basic no-no.

I'm puzzled about the position under a fence. Unless the builders were very careless when putting it in before fences went up, it would make me wonder about the boundary. Rather silly of your neighbours to bury it as well.

 

[jb1468]

Current regulations call for just about everything to be 750 - 1,000 mm deep and I doubt it was much different in the 60's .

That apart however, must you bury this post ? If there are enough others buried, could you not simply sit this one on a flagstone, maybe flush with the surface of the soil for aesthetic reasons ?


Have never laid decking, so apologies to anyone if I have just contravened some basic no-no.

I'm puzzled about the position under a fence. Unless the builders were very careless when putting it in before fences went up, it would make me wonder about the boundary. Rather silly of your neighbours to bury it as well.

Thanks for the estimate - very helpful and I have once before questioned boundary lines for a whole different reason - ended up at solicitors checking the papers etc. Turns out they are in the right position and simply put the builders who built the set of houses (ex council) for whatever reason has put it there - helpful not!

I guess I need to explain the decking in-case any other readers wonder about this one post. The vast majority of decking will have a solid concrete base which is in situ. The plans (which I could change but don't want to at this stage) require it to move out somewhat into the soiled area at an angle. I cant change the angle for height variation reasons and that angle unfortunately runs right along the edge line of the decking which is right along the line of the sewage pipes (assuming they run in a straight line). As I said I could move in but not out and loose some decking but I'm already compromising the size. To come in would just look silly. In short for the deck to have proper support in the soiled area it needs 2 posts minimum. One should be OK the other which regardless if where it goes along the line risks hitting the waste pipes if they are not low enough. I will not go down as far as standard with this post to avoid any potential problem as the rest of the support should compensate. counting this support post the decking frame is certainly not over supported or over engineered. Cant afford to compromise any further with supports.

If drain in the way i will have to change plans

Thanks

 

[RedHerring2]

Why not put your plans on here to see if someone can come up with a canter-lever option or similar?

 

[jb1468]

Why not put your plans on here to see if someone can come up with a canter-lever option or similar?

Thanks for the thought. I don't have the plans in writing just a rough out plan and the rest in my head. I suspect on further reading and estimated measurements given here that the depth of pipes in situ should pose no significant problem. If I'm wrong then i may well post again with more detailed plans on decking and obstructions with the hope that someone can indeed come up with an alternative.

A cantilever option is something that I may indeed need to think about and until your prompt I hadn't. Thanks for the prompt