Lintel height limit on rear extension

[dearface]

Hi

I'm looking to single floor extend the rear of my house for more kitchen and living space. In investigating the structure further, I have discovered a slightly unconventional feature at the back of my semi detached house; a concrete lintel that spans, single piece, both my property and across to my neighbours house. The lintel would sit at around 2000mm off the extension floor.

My structural engineer is of the view it's too risky to both houses to cut the lintel (and fit a new lintel around 600mm higher on my property). This leaves me with few options other than to can the extension completely or accept the lintel spanning the inside of the extension at a height of 2000mm (length circa 3800mm and depth circa 200mm). A ceiling height of 2400mm can be achieved either side of the lintel inside, however the lintel structure is certainly going to be noticeable!

Questions:

Do people have experience in living with an internal lintel/beam structure at around 2000mm? Do people find it tolerable? Are there interior design features people have adopted to 'soften' the visual impact? Or have people found 2000mm to be simply too low?

More generally, has anyone come across this problem before with lintels spanning both properties of a semi, and whether theres anything i coulld suggest to my engineer to investigate?

Further context: its a 1950s semi detached, no one in the family are giants.

Thanks

 

[endecotp]

I have a beam at that height in my bathroom, where it is just about OK once you are used to it. It would be very odd in a principal room.

How about having a lower floor level in the extension, with the new ceiling at the lintel level and steps down? If you were to separate the kitchen-area from the living-area at that point, and if the outside ground were sloping downhill, that could look OK.

Otherwise... they say it's always possible to engineer a solution if your pockets are deep enough.

 

[noseall]

Hi

I'm looking to single floor extend the rear of my house for more kitchen and living space. In investigating the structure further, I have discovered a slightly unconventional feature at the back of my semi detached house; a concrete lintel that spans, single piece, both my property and across to my neighbours house. The lintel would sit at around 2000mm off the extension floor.

My structural engineer is of the view it's too risky to both houses to cut the lintel (and fit a new lintel around 600mm higher on my property). This leaves me with few options other than to can the extension completely or accept the lintel spanning the inside of the extension at a height of 2000mm (length circa 3800mm and depth circa 200mm). A ceiling height of 2400mm can be achieved either side of the lintel inside, however the lintel structure is certainly going to be noticeable!

Questions:

Do people have experience in living with an internal lintel/beam structure at around 2000mm? Do people find it tolerable? Are there interior design features people have adopted to 'soften' the visual impact? Or have people found 2000mm to be simply too low?

More generally, has anyone come across this problem before with lintels spanning both properties of a semi, and whether theres anything i coulld suggest to my engineer to investigate?

Further context: its a 1950s semi detached, no one in the family are giants.

Thanks

2m is tight for door casings, tall kitchen units etc. And that's without plaster and floor coverings to take into account. As long as the design is clever enough to avoid it then crack on. I might bite the bullet rather than live with it though.

 

[jj4091]

Could you create a false arch by using something like this in the corners. I did that in similar situation and have lived with it for 25 years without it being a problem. https://www.diy.com/departments/exp...MIsaSmlsXwjwMVyJVQBh0ybgbTEAQYAyABEgLFV_D_BwE

 

[dearface]

2m is tight for door casings, tall kitchen units etc. And that's without plaster and floor coverings to take into account. As long as the design is clever enough to avoid it then crack on. I might bite the bullet rather than live with it though.

Thanks. Downstand beam is in the dining room area so wouldn't require any kitchen units thankfully.

Introducing a step to increase floor to ceiling height was suggested but my architect is of the view that it increases cost and complexity considerably. (Budget constraints another factor here!)

 

[mrrusty]

My structural engineer is of the view it's too risky to both houses to cut the lintel (and fit a new lintel around 600mm higher on my property

I think you need a second opinion. The lintel spanning both houses must be supported on the party wall. It is very difficult to envisage why this can't be cut and a new lintel engineered to sit on top of the cut end, or even a goal post structure. Just because SE #1 can't see the solution, doesn't mean there isn't one

 

[stuart45]

There will be a solution, but it depends how much cash he wants to throw at it.

 

[cdbe]

I'd seek a second opinion - he must think the reinforcement will fail in some way when you cut it - but I can't see how? Perhaps leave a short section on a nib in your half.

Otherwise a bigger extension.and convert the centre area to an office/utility/WC.

 

[stevie888]

If it's a 50s build then chances are it's a cast in situ lintel and the single piece was simply for ease of build.

A beam spanning 3 supports is effectively stronger than a single beam of half the span as some of the bending effects are taken as HOGGING moments over the central support. The proviso is that the supports have to be spot on and the beam designed appropriately. If cast in situ then the beam will fit perfectly until there is movement in 1 of the supports and then things can get complicated. For this reason the vast majority of domestic beams are designed as SIMPLE beams with just 2 supports.

I think your SE is being unduly cautious (easy to say over a forum of course!). Unless he thinks it might be a post tensioned beam??

I would be looking at introducing an independant support on your side for your new beam (steel post) and cutting the lintel at the face of your wall so it still bears fully on the party wall.

Second opinion time!!

 

[dearface]

If it's a 50s build then chances are it's a cast in situ lintel and the single piece was simply for ease of build.

A beam spanning 3 supports is effectively stronger than a single beam of half the span as some of the bending effects are taken as HOGGING moments over the central support. The proviso is that the supports have to be spot on and the beam designed appropriately. If cast in situ then the beam will fit perfectly until there is movement in 1 of the supports and then things can get complicated. For this reason the vast majority of domestic beams are designed as SIMPLE beams with just 2 supports.

I think your SE is being unduly cautious (easy to say over a forum of course!). Unless he thinks it might be a post tensioned beam??

I would be looking at introducing an independant support on your side for your new beam (steel post) and cutting the lintel at the face of your wall so it still bears fully on the party wall.

Second opinion time!!

Thanks for this.

I may be misunderstanding, however does what you're saying not suggest that cutting the continuous beam in half, effectively at the mid point of the central support, may result in a weakening of the remaining (neighbours side) structure, particularly given the apparent sensitivity to movement?

Is there any visual clue as to whether a beam is post or pre tensioned?

 

[Ivor Windybottom]

I'm going to give a second opinion that you need a second opinion!

I really can't understand how cutting it could cause an issue. If they're making such an extraordinary claim then they need to provide extraordinary evidence of exactly what they think the issue would be. Don't leave it at gut feeling, guesstimation and people on the internet guessing at why.

Obviously leave your neighbour with some support from your length of the wall if necessary, at least the same length that it has on the other side of their opening. Don't just chop at the party wall and say sod em.

 

[Ivor Windybottom]

To clarify, the outcome may be that you end up with a stub wall jutting into your new room holding up the end of the lintel for your neighbours' benefit, if the structural engineer decides that it needs more support than it gets from the wall on their side of the boundary alone. But hopefully this could make a lot more sense than having a pointless low beam across the entire room.

But I'd hope that it turns out it would be fine if chopped back to the party wall, but that's down to actual calculations by someone who knows what they're doing. Which a structural engineer should be able to do, if not then get another.

 

[stevie888]

Thanks for this.

I may be misunderstanding, however does what you're saying not suggest that cutting the continuous beam in half, effectively at the mid point of the central support, may result in a weakening of the remaining (neighbours side) structure, particularly given the apparent sensitivity to movement?

Is there any visual clue as to whether a beam is post or pre tensioned?

It's highly unlikely to be post tensioned: this is proper structure land

 

[stuart45]

A 50's house with a lintel of that size was probably cast in situ with the rebar (hooked ends) laind in place as it was cast.

 

[Deluks]

The other slightly more expensive option is to approach the neighbour and suggest removing the beam entirely and replacing with steel higher up, your neighbour may appreciate the extra headroom too, the question is whether they want to share any of the costs. You could offer to pay for calcs, BC and insurance, if they go halves on materials and labour. Can't hurt to ask?