Building over a culvert?

Saw a house today that we would like to have. At the moment it has an integrated double garage, which of course is a wood store, shed, workshop... Ideally the space could be used to make a bigger and better kitchen than already exists.
There is a natural site for a three bay garage/shed. The shed site has a 18 inch plastic culvert running through it to take a very small stream through the site and then on into the garden.
I'm thinking a reinforced slab dropped over the site would be sufficient with perhaps the addition of retaining walls either side of the culvert pipe? Anyone done something similar?
 

Old Stab

LE
Book Reviewer
Mini digger.
Divert it out and away and make sure it doesn't get blocked.

Dig it deep to allow for extra water flow
 

MrBane

LE
Moderator
Kit Reviewer
Reviews Editor
Hi there.

Open it up, build around it and you can have a lovely water feature running through the garage.

Thanks.
 
I can only imagine the red tape hoops you'd have to jump through to build over a culvert. Even diverting it might not be straightforward from an officialdom perspective.
 
Do a little bit of investigation ( Internet, council, local pub ) about whether there has been any flooding in the area. ( Or near misses - its only going to get worse.)

After that is done , a couple of photos , a few dimensions and the power of ARRSE will come up with a stream diversion that will keep your house dry, chill your larder, power a generator and provide fish for the rest of your days.
 

Blogg

LE
I can only imagine the red tape hoops you'd have to jump through to build over a culvert. Even diverting it might not be straightforward from an officialdom perspective.

The magic word is "Watercourse" which the Environment Agency define as "any natural or artificial channel above or below ground through which water flows, such as a river, brook, beck, ditch, mill stream or culvert."

At which point the madness may start, because you probably have an "ordinary watercourse" and anything beyond ordinary maintaining and repair requires the dull evil of bureacracies.

 

Tunnels

War Hero
What's upstream from the culvert? How big's the catchment? If a load of muck/trash/veg gets washed down and blocks it, congratulations your house is now a dam.

Is the culvert big enough?, it's not a hard calc Google "time of concentration" and "UK rainfall map".
 

RangdoOfArg

LE
Book Reviewer
Check very carefully with the local water authority and the environment agency. If it’s a plastic culvert, someone put it there and recorded it.
If you go ahead and buy the property, it could well be recorded as a land charge (if you are in England or Wales). These are recorded against the property.
Long story short, it could be that A N Other is allowed access to what could be your land to access the piping. And if you have built over that culvert, there might be nothing you can do about them gaining access.
Lots of information on Local Authority websites. If you get really serious about the property, get the conveyancer to earn their fee and search thoroughly.
 
Alternatively build a manhole cut the top off the pipe this will give you access if there is any problems
 

RangdoOfArg

LE
Book Reviewer
OP, just to add…you can’t beat a bit of fieldwork. Providing you are local, go along and have a look at the lie of the land. If it’s drainage, have a good look after heavy rain and look at the ‘before and after’ situation.
A ‘very small stream‘ can be a lake within hours.
And it could be your problem, not the water authorities.
If it all checks out, and you like the house, hope it all does well.
 

Joshua Slocum

LE
Book Reviewer
Saw a house today that we would like to have. At the moment it has an integrated double garage, which of course is a wood store, shed, workshop... Ideally the space could be used to make a bigger and better kitchen than already exists.
There is a natural site for a three bay garage/shed. The shed site has a 18 inch plastic culvert running through it to take a very small stream through the site and then on into the garden.
I'm thinking a reinforced slab dropped over the site would be sufficient with perhaps the addition of retaining walls either side of the culvert pipe? Anyone done something similar?
You need a surveyor,
Usually you dig the ground around it away, set concrete. Footings either side but not touching it, then a concrete lintel across the top to take the weight
Also if it's a big garage, install a manhole with access trap to floor level in case of blockage
I am away from home for a while, so my reference books are not handy
Check with building control for the specs
 
Three car garage you say, you could always go energy independent.

Waterwheel-1__FillWyIxMDI0IiwiMTUzNiJd.jpg
 
OK - Stand easy.
Had a quiet look around today, as I knew the current owners are away. There is clearly some problem with the septic tank, it's position and the outflow in relation to the house and potential garage site. A submersible pump was in use which was not there yesterday. We've had no noticeable rainfall for several days, so I suspect there is an issue that has yet to be discovered...not by me though.
Thanks for all the advice and thoughts.
 

rgjbloke

On ROPS
On ROPs
Diverting it means a lot of digging.

I’d put a concrete pad stone either side of the pipe and lay a couple of pre-stressed lintels across the top of it.

The pre-stressed lintels are available at any decent builders merchants in a variety of sizes depending on what you intend building on them. A ton bag of ballast, half a dozen bags of cement and a sheet of shuttering ply would probably set you back about a hundred quid.

Probably a days work for two guys.

Job jobbed.
 

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