Can I build a house extension over a manhole?

Howdy folks.

I'm just sitting here dreaming up my future plans for the house. How great it'll look, how it'll do this, do that, etc. and I realised i have a back garden with not one, but two manhole covers.

When I say manhole cover, I mean a circle about 3ft/1mtr in diameter.

A quick Google tells me that due to their size, my manhole covers most likely belong to a public sewer and serve several houses (I live in a house estate, and my house is the corner on an L shape of two rows of houses).


Both manhole covers are at the bottom of my garden, about 15ft away from each other. Both look identical. As my house is on the corner of an L shape, i presume each cover serves the houses going in each direction from me (ie; one for one side of the L and the other for the other side of the L).

Would I be correct to guess that both of these are connected to each other (so theoretically, you could cover one and maintain access via the other one?).

Adding to this, about 30ft away, outside my garden (there is rear access to these houses, so on public land) there is yet another manhole. Although the placement of this one seems random and doesn't line up with the others.


The manhole outside my property takes my interst because I wonder is it a case that the council forgot that my manhole covers are there, so use this one for access?

I say that because in the last, approximately 30 years, no one has ever come to check, lift, look at or even enquire about the manhole covers in our garden. My thinking is the Council put them in the garden, perhaps realised what a poor idea that was, and so diverted them elsewhere onto public land for ease of access?

there's also, about 70ft away from one of the manholes, another manhole, that lines up with it, in front of the house. I presume this is a continuation of the underground pipe?


My long term house plan would be to extend over one of the manholes (not both).

Would I be right in guessing that if no one has looked at them in nearly 3 decades, that i'm safe enough to just cover them and ignore them?


I realise my description is shoddy, but I'll try get a photo up if it's needed. Not sure if my issue is really an issue or if I'm making one where there is none?

Also, if i needed to get someone who knows about this kinda thing to look at it, what kinda tradesman or occupation would I be looking for? I wouldn't like to ring Irish Water as I don't want to accidentally inform them of manhole covers they might not know about, and accidentally get caught up in all the red tape of covering one by opening my mouth when I mightn't need to.


Cheers

BryanF

Civil engineer

Site visit

garbo speaks

My parents built their extention in the rear garden over a manhole. The manhole is double-sealed (in their utility) and everything is fine.

JimFin

Given that the purpose of a manhole is for service access then it is unlikely that one of them is a spare, it is required as part of the services design to allow access to some section of the sewer network. You don't really want to be having any servicing of a sewer line in your new extension. Secondly I would be concerned that any malfunction of either smells or overflow could occur and manifest itself in the new extension, so to cover them over and hope that solves it would be risky decision.

I would say the first thing to look at is can the sewer line be rerouted/re-designed so that it is not going through your extension, or that it at least does not require a manhole inside the extension. If it is a public sewer line then it will be up to Irish Water to reroute it, you should request an IW engineer to call out to survey the line initially. If it is your own domestic connection to the public sewer then it will be your responsibility and you just include it as part of the requirements of the new build. In the overall cost of the build this would be a small enough but worthwhile addition.

sydthebeat

http://www.irishstatutebook.ie/eli/2007/act/30/section/104/enacted/en/html


in a nutshell, you need permission for the "relevant water services section" to do what you are asking, irregardless of whether the extension is exempt from planning permission or not.

Zoney

JimFin wrote: »

If it is a public sewer line then it will be up to Irish Water to reroute it, you should request an IW engineer to call out to survey the line initially. If it is your own domestic connection to the public sewer then it will be your responsibility and you just include it as part of the requirements of the new build. In the overall cost of the build this would be a small enough but worthwhile addition.

Unfortunately, if it's a shared sewer, it's now magically become private (shared) not public and Irish water won't have anything to do with it. Up to you and the neighbours to figure things out.

Have to get the neighbor who has the house where it connects to the sewer in the road to get onto them anytime it backs up (does actually block at the road but they just look at a map and won't come out for me).

Similar planned extension issue here and due to any possible blockages and problems, no way would the hatch be going inside!!

Gumbo

Zoney wrote: »

Unfortunately, if it's a shared sewer, it's now magically become private (shared) not public and Irish water won't have anything to do with it. Up to you and the neighbours to figure things out.

This has always been the case.
Everything is private until the outfall connects to the main line on the street.

Zoney wrote: »

Similar planned extension issue here and due to any possible blockages and problems, no way would the hatch be going inside!!

+1

I would always try design the manhole outside of the extension and provide rodding access externally.