Lintel advice for below ground level

[JulianB]

Afternoon All,

 

We've finally managed to lay the foundations after having excavated the best part of 500 tons to clear site together with the challenging underpinning and retaining walls. We're now onto the build to the underside of the beam and block floor / DPC and things are looking pretty tight in terms of underground drainage. Due to us not having a great deal of space under the floor (150mm), we do not have the luxury of installing a concrete lintel above the openings for the soil pipes. As a result I've been thinking if a galvanised single leaf angled lintel would do the job or if this is a 'no no' being under external ground level, however not in direct contact.Not really sure what other low profile lintels are out there, and the exits are perpendicular to the direction of the beams and hence would require the flooring blockwork and slip bricks to rest on these sections.

 

Would anyone have any suggestions?

 

Thanks!

 

Julian

[Temp]

 

I think I would wrap short lengths of pipe in insualtion and lay them cross the top of the foundations. At some point cast them in concrete. If the beams of the B&B floor go either side of the pipe your cast concrete can replace a block and form a lintel.

 

 

 

[Brickie]

If your pipes are tight to the floor can you not lay two courses of engineering bricks (so 150mm high) either side as your lintol bearing,and bed a standard 100mm x 65mm concrete lintol level with your first course of blocks? (225mm to top of lintol.)

[JulianB]

On ‎06‎/‎08‎/‎2020 at 18:57, Temp said:

 

I think I would wrap short lengths of pipe in insualtion and lay them cross the top of the foundations. At some point cast them in concrete. If the beams of the B&B floor go either side of the pipe your cast concrete can replace a block and form a lintel.

 

 

 

 

Hmmm I don't think I quite understand this approach. Are you saying to use a pipe wrapped in insulation as a form to cast some concrete which would then carry the weight of the block floor?

 

On ‎06‎/‎08‎/‎2020 at 19:23, Brickie said:

If your pipes are tight to the floor can you not lay two courses of engineering bricks (so 150mm high) either side as your lintol bearing,and bed a standard 100mm x 65mm concrete lintol level with your first course of blocks? (225mm to top of lintol.)

 

The problem with that approach is I would no longer be level for the last block coming off the beam, to the perimeter of the inner leaf  if that makes sense

[Temp]

8 hours ago, JulianB said:

Hmmm I don't think I quite understand this approach. Are you saying to use a pipe wrapped in insulation as a form to cast some concrete which would then carry the weight of the block floor?

 

Yes but not as a form.  Actually use the pipes cast into the concrete block. Its quite common to run pipes through the foundation pour. The insulation allows a bit of movement due to settling but that is really only important when using clay pipes that can crack.

 

You might also be able to put the beams of the b&b floor either side of the pipe and replace a block with a lintel. 

 

I'll try and make a drawing in a moment.

 

 

[Temp]

[Temp]

Aside: If your pipes are this high is there enough room to fit the required large radius bends at bottom of stacks and ground floor WC?

[Russell griffiths]

25 minutes ago, Temp said:

Aside: If your pipes are this high is there enough room to fit the required large radius bends at bottom of stacks and ground floor WC?

There’s normally lots of room for the rest bend as you have the depth of the beam to play with. 

[JulianB]

3 hours ago, Temp said:

 

Thanks for that, now it makes a lot more sense! Unfortunately I'm exiting the underfloor space perpendicular to the beam direction and hence the blocks would be spanning the final section and resting on the inner leaf. I think if I had a block bigger than 440, then I could happily span across the underground drainage opening in the inner leaf, not sure what other options I've got...

 

2 hours ago, Russell griffiths said:

There’s normally lots of room for the rest bend as you have the depth of the beam to play with. 

 

I'm hoping that if it is very close I could get away with the rest bend protruding through the beam and block floor seeing as we've then got the insulation and screed, and live with the bigger opening in the block... which would then be covered by the insulation and screeded over?

[Russell griffiths]

Having the bend collar protruding above the beams is exactly what you do, you will have at least 150mm of insulation above the beams so plenty of room to adjust to what you need poking up. 

You should ideally have the beams design done so that a beam doesn’t sit directly over a pipe. 

In the grand scheme of things a 110mm opening doesn’t even need a lintel as long as there is no direct load over it. 

[Temp]

4 hours ago, JulianB said:

I'm exiting the underfloor space perpendicular to the beam direction and hence the blocks would be spanning the final section and resting on the inner leaf. I

 

I think you might still be able to cast your own block/lintel.

[Russell griffiths]

If you go and get a length of pipe 150mm and cut it into 600mm bits you can do a sleeve over your pipe and surround in concrete. 

[Gus Potter]

For all. In a case like this if you get really stuck then you can sometimes use a thick steel plate, 40 - 50mm. You may be able to pick up an offcut from a fabricator ect as this can be a common heavy industrial column base plate size. To do it all correctly then you want to protect it, if it rusts heavily it can swell and lift stuff so galvanising is one way to go. Alternatively if you're happy then clean the steel, spray it to death with galvanising spray and carry on.

 

Russel makes a good point. Have a look at what is above, point loads and so on. If the load above is spread out evenly and you have a good few courses of brick above then the load (conservatively) spreads out at 60 deg, you'll often see 45 deg mentioned.

 

This trick can come in handy when doing renovations / conservation work, sometimes you'll use stainless steel.

 

I'll try this but here is a link to let you see that plates this thick are standard @ 100mm wide so you may get them at a sensible price.

 

https://www.parkersteel.co.uk/Matrix/10/Steel-Flat-Bar

 

 

[Onoff]

47 minutes ago, Gus Potter said:

galvanising spray

 

Blasphemy! No such thing! ?

 

If you must use zinc rich spray then good old Galvafroid takes some beating. Been trialling Zinga of late too.

 

 

[Gus Potter]

I think I have blasphemed more than once onoff!

 

It could have been worse, I could have mentioned "screwfix spray" ! and what then. Just a thought, I mentioned conservation work and stainless steel.. is that one of my blasphemes?

 

Your right about the spray. How are you finding the Zinga any good? 

 

 

 

 

[Onoff]

6 minutes ago, Gus Potter said:

I think I have blasphemed more than once onoff!

 

It could have been worse, I could have mentioned "screwfix spray" ! and what then. Just a thought, I mentioned conservation work and stainless steel.. is that one of my blasphemes?

 

Your right about the spray. How are you finding the Zinga any good? 

 

 

 

 

 

Tbh I like this stuff if I'm buying it. 

 

https://www.toolstation.com/cold-galvanising-spray-400ml/p60070

 

Keep meaning to cut a plate into a few bits and spray with various zinc paints and see how they fare in my particular location. (Bottom of a constantly damp valley).

[Gus Potter]

Ta onoff. Not enough hours in the day.. if you get a chance go and post how you got on with that.