Building Regs: New Staircase/Alteration of trimmer

[drewks]

Hello
I'd be REALLY greatful for some advice here please! I realise that my question should fall into the building forum too so apologies if that is the case.
I'm putting a staircase into an existing mezzanine area after reinforcing it to B Regs requirements.
I'll have to remove the width of the new staircase from the trimmer to allow it to be fitted, and this is the question...
.....do I have to employ some clever person to work out what size timber is needed to support the trimmer (for B Regs)? Or can someone help me on this (PLEEEAAASE!) as I can't really afford to do this! Or is it a question I can realistically ask my B Inspector?
The mez. floor is 2.45m x 3.04m (the latter is the trimmer length), and the trimmer itself is 5" (125mm) x 4" (100mm).
Also I presume that this column/support would have to go from floor to ceiling?
Many thanks for your time in reading this and even more for any replies!

 

[^woody^]

I can understand what you are doing, but your terminology is a bit confusing.

Basically just double up the joists supporting the trimmer and maybe the trimmer too

I'm confused about the "column support" too. If there is a column, and if it is supporting something, then then yes it goes from floor to ceiling. You may need to check the load and ground floor thickness, to make sure the ground floor is adequate to stop any column punching through it

 

[drewks]

Hi there Woody
Thanks for your reply.
Sorry for any confusion!
Basically what I call the 'trimmer' is the main joist running the width of the room and this is supporting the other joists (obviously at right angles) on hangers. The staircase is going up a wall, a wall that the trimmer is set into, so the 'end' 90cm of the trimmer has to be removed.
The support I'm asking about is the support of the 'free' end of this existing trimmer once the section has been removed.
Hope this is a bit clearer!

 

[^woody^]

No, still not there

This trimmer sounds like a beam, if all the other joists are off it. And if you are cutting this beam then you need another to support it - and thus support the whole floor. Unless that is what the column is doing?

As previously, doubling the joist normally does it. But its still hard to picture it, as the loads may be significant if all the floor is off one beam which is then to be supported off another

 

[drewks]

Sorry, I know it's me not you!!

Yup you probably WOULD call it a beam, and it IS this that I will need to support by means of a column or similar at the point where it's being cut off short of the wall to accommodate the staircase. And yes, it IS supporting the joists and therefore the whole floor.
Whoh - this is hard to explain!!

Will try and do a drawing but that may not make it much clearer!

 

[drewks]

...ok, have done a very basic sketch plan - hope this makes it a bit clearer...

Not at all familiar with how to upload and show images - sorry - this is obviously the first one shown Hope it's visable!



//media.diynot.com/34000_33291_50255_93926341_thumb.jpg

 

[^woody^]

Haven't you posted this previously? I recall something similar

Anyway, if you really can't get the flight in with out cutting the joist, then just cut it. Then double up the joist which will be along the side of the flight and which will hold the trimmer across the top step.

The post/column will need designing. A 100mm2 post might do

 

[gregers]

i think the confusion here is not knowing the correct terminology for each item/piece,so here goes
trimmer/trimming and trimmed,funny ive still got the books when i was learning all this bumph,

http://books.google.co.uk/books?id=...page&q=trimmer trimming trimmed joist&f=false

 

[drewks]

Nope, not me Woody.

One thing I forgot to mention (D'OH!) was that the head of the stairs will have to be set further back from the joist/beam/trimmer (thanks gregers!!) as the required headroom on the mezz isn't high enough directly above it; therefore it HAS to be cut and then supported....

"..The post/column will need designing. A 100mm2 post might do"

....this is what the post is all about! Would a 4" post do for this size and would I need workings out etc etc?

Thanks again

 

[drewks]

...STOP PRESS!!

...you're right Woody, I did ask a similar question a while ago; this is slightly different tho!

 

[tony1851]

Is this what you're on about?
If so, BC will almost certainly ask for some figures for the post, and also whatever supports it at the bottom (remember that the post will be supporting about 1/4 of the floor load.
You will also need to ensure that the whole structure remains stable by being adequately tied to the walls.

Untitled

• tony1851
• 18 Sep 2012
• 1

 

[drewks]

That's very close to being it Tony - many thanks!
Who would I get to work these figures out and put a solution together for the post, as you call it (VERY limited budget!) - and would that have to continue to the ceiling and tie up there?

Thanks again!