Build over sewer lintel design

[adwt2004]

Hi,

I'm curious about what lintels you guys use to build over a sewer. My SE has specified 100wide, 150 deep, 1.8m length. Presumably they will be sat on the blocks either side tall side up.

Is this the sort of specification that normally is prescribed for this? It's single storey rear extension which is near and clipping the top of the sewer on one corner. Its rear wall runs slightly diagonal to it.

Just asking as they are pricey! Thanks

 

[freddiemercurystwin]

Why are they so long? I would expect they only need to be about 750 long (or less) assuming a 150 pipe and 150 clearance all around.

 

[adwt2004]

They're that long due to the design and what's needed so that the building sits on top of them. It's a clipped build over.

1

• adwt2004
• 25 Jan 2018

I guess making the extension longer could shorten them but then it falls foul of PD.

 

[Ian H]

That's an off the shelf, £15 lintel isn't it?

 

[adwt2004]

Is it? 100w x 150d, 1.8m length? Links welcome as I can only find them at around 50-60 quid and I need quite a lot if I have to butt them together over 4m

 

[^woody^]

My SE has specified

Lol. #FakeSE.

He's an idiot too with that design. Jeez.

 

[adwt2004]

I am where I am. He is qualified, I've checked.

 

[Ian H]

Maybe your right:

https://www.travisperkins.co.uk/Sup...te-Lintel-100mm-x-140mm-x-1800mm-R15/p/701605

http://www.less2build.com/prestressed-textured-concrete-lintel-100x140x1800

140 is the standard size rather than 150.

 

[adwt2004]

Yeah I've contacted the SE to see what the score is and what options there are. I'm presuming he wants the lintels 150mm upright so maybe I can get ones which are a different width. Or change to the 140 standard.

I'm no specialist with se but I think this is overkill. Trouble is the water company does want this and the SE had to fit in with it.

 

[Ian H]

Getting better:

http://pbsltd.org/product/1040/type...0x150x1800mm/dcc379602b2c5e8ddfdaf553b84a676b

But buying 40 of them? Seems madness.

 

[adwt2004]

I think the whole area is to be bridged due to the corner point load and then the sideways load from the rest of proposed building. I've asked the SE about sizing it to 140 and whether they need to be butted together or can be spread to say Lintel - 50mm Gap - Lintel etc.

 

[^woody^]

It's nonsense however much he is qualified. He's not paying the bill.

The loading from the building is only potentially acting near the section of drain right by the corner, so all that silly lintel spanning is completely unecessary.

What that design is going to do, is actually load the lintels and load the ground on the other side of the sewer too. That is unnecessary in terms of protecting the sewer, and just adds risk of movement to the building and adds unnecessary cost. And all for no reason.

 

[wessex101]

I'm inclined to agree with Woody, that is a bonkers design. I would form the foundation as normal but leave out the corner nearest the drain. Form a foundation pad on the opposite side of the drain so you only need to bridge the corner.

Another option would be to re-route the drain.

 

[adwt2004]

I’ll have to give it some thought.

Normal foundation pour and then lintels across the corner are certainly easier and cheaper.

Not sure how easy it is to change this now though as Wessex and the council have agreed with it.

Is it something a BCO can advise on if I raise it?

 

[John D v2.0]

You can download the guidelines for build over online, basically depends how deep the sewer and how close you are.
Then you can work out as above how much is fine in its own right and how much needs bridging.