Return on internal wall

[acurachris]

Hi

I am slowly constructing my extension and everything has been going okay until I stumbled upon an article regarding openings near a wall return.

It appears you need a 550mm internal return at an external corner although i'm not sure about my instance. It is an internal wall and I have an internal return of 120mm at the minute. I was going to run the concrete lintel (over internal door) to the corner creating a 220mm bearing.

Is this okay as it's not an external corner of the house or do i still need a 550mm return without SE calcs?

Cheers for any help.

 

[^woody^]

That requirement you have read is for a different situation to what you have there.

Whay are you building an internal wall in cavity?

 

[acurachris]

Hi

Thanks for the reply. Is the 550mm just for external windows and doors near the corner then?

The original design was to have a two storey extension with a part single storey, so this doorway is from the ground floor of the two storey section into the first storey section. The cavity wall would form the two walls of the two storey.

We have applied since to have the single storey converted to two storey although planning hasn’t been decided yet.

 

[acurachris]

I've just had a thought about this cavity wall and I'm actually starting to worry now!

Where the two storey and first storey extensions meet and share the cavity wall at ground floor level, both walls are built in celcon lightweight blocks, but where it converts at first floor to two storey, the outer wall is the brickwork of the two storey so they'll be 29/30 courses of facing bricks (plus gable end) on top of the 10 high celcon block wall. Hope that makes sense - see if the picture adds any clarity! Is this a problem for the celcon blocks taking the weight of those facing bricks, because now i'm thinking they are only designed to take the weight of celcon blocks?

I should have been an artist - i know!

Whay are you building an internal wall in cavity?

Should it be done another way? I did consider just running the block and brick cavity all the way around the outline of the extension and using steel lintels to support the first floor walls, is this considered better practice? I just thought it would be better to have solid walls supporting.

I've only built four high blocks so i can change the way i build this wall if needed.

Cheers

 

[tony1851]

The Celcon will be perfectly adequate to support the brick skin.

PS, the internal returns you have are fine. As W said, what you read was for different circumstances.

PPS Why have little 100 returns anyway? - just bond the inner skin from each side and run the concrete lintels direct onto the inner skin. That way, you won't have that awkward and unnecessary bulge where the door frame is.

 

[acurachris]

Thank you.

Just copied this from the building reg plan, it does show on there the way i've built it with the cavity.

 

[noseall]

Just copied this from the building reg plan

….except you forgot to show the window....which will have a lintel....which may have clashed with your doorway lintel....hence the nibs.

 

[Leofric]

Not being funny but if you already have building regulations approved drawings why not just build to them and if you have any technical queries ask the person who produced the drawings, that would be the normal practice.
Regards

 

[acurachris]

….except you forgot to show the window....which will have a lintel....which may have clashed with your doorway lintel....hence the nibs.

Yes, fair comment, it wasn't intentional, do you think that will make a difference?

Not being funny but if you already have building regulations approved drawings why not just build to them and if you have any technical queries ask the person who produced the drawings, that would be the normal practice.

You know, i've just had a wobble the last few days, but yes you're right i should've followed the plans (as i have done so far). Reading a couple of articles got me worried things weren't correct. The guy who did the drawings doesn't offer that service, he is a plan drawer and that's where his service ends. That's a big lesson learnt for future.

 

[noseall]

Yes, fair comment, it wasn't intentional, do you think that will make a difference

No, as long as you can seat both lintel bearings adequately. The window itself however does need to be a minimum distance (665mm external meaurement) from the corner.

 

[acurachris]

No, as long as you can seat both lintel bearings adequately.

Thanks, that building regs drawing makes the window look like it's right up to the wall, but it's not that close, it'll be a 900mm window and they'll be about 250mm to that internal reveal. (550mm from external corner/900mm window/250mm to that internal cavity/nibs)

EDIT: that 550mm measured internally - just meant the external corner of the extension!

 

[tony1851]

I know it's in the Approved Document A, but that 665mm figure we always see is only advisory. It could reasonably be reduced if it's only a window near the corner; if it's a heavy patio door or bifolds, that's a different matter.

 

[acurachris]

PPS Why have little 100 returns anyway? - just bond the inner skin from each side and run the concrete lintels direct onto the inner skin. That way, you won't have that awkward and unnecessary bulge where the door frame is.

That would speed up the block work a bit (i'm not the fastest!), however that would only give me 100mm bearing for the lintel rather than up to 200mm bearing with the nibs (told to use 1200 x 140 x 100 concrete lintels for internal doors or door width + 150mm either side). Do you think it'd be stronger bonding that block wall together and running the lintels as you said? The rest of the two storey brickwork would then be laid above those lintels.

EDIT: When i say told to use.. i mean my building regs say...

 

[Leofric]

'The guy who did the drawings doesn't offer that service, he is a plan drawer and that's where his service ends. ' - don't understand this -anybody who prepares architectural drawings should be able to answer any queries on their drawings ! As far as the dimension to the window is concerned , the drawing specifies an ' internal reveal of min 550mm ' !

 

[Leofric]

' I know it's in the Approved Document A, but that 665mm figure we always see is only advisory ' - or to be justified by a structural engineer if a smaller dimension .