Advice on RSJ's

[smilerbatten]

Hi All,
I have just finished building an extension and want to now knock through from the existing house to the new extension. Originally i had planned to put in two steels and rest them at either side of the existing house and have the kitchen / dining room dividing wall as a pier, but i have since thought it would be nice to completely open up the back of the house and have one 5.7m RSJ cover the complete span. this means i can knock back the kitchen / dining room dividing wall to open up the kitchen layout.

Is this a good idea, can i simply get a structural engineer to calculate the beam size or does going this long mean i have to make other considerations? some people i spoke to mentioned i might need to have a picture frame style steels made to hold this arrangement..

I have attached a copy of the old and new floor layout, its a pretty std 1930's semi, The opening I am making at the back of the existing house to open it all up is 5.7 meters wide (width of the house), holding 200mm thick brickwork @ 5.7m long x 2.4m high above it.

Untitled

• smilerbatten
• 9 Aug 2010
• 1

Any advice on whether i should go for the single steel, go for two seperates and leave a pier where the dining / kitchen wall is?

Any advice would be appreciated.

Thanks
Jason

 

[freddiemercurystwin]

A steel at that length will end up around 300mm deep, this can be shoehorned into the floor zone above to raise it up at further expense. You'll also need a sizeable column at each end where the hit the external walls, these may require pad foundations. Having two smaller steels and a mid-span column will likely be cheaper. Any decent structural engineer will be able to do some fag packet calcs in about 5mins and give you a steer as to the most suitable solution, goal post solutions included.

 

[RonnyRaygun]

A box frame would probably be the best solution here. This involves a goalpost frame as Freddie said, with both columns sitting on a base beam the same size as the top beam. I reckon you would need 254 UCs top and bottom and 203 UCs as columns.
The base beam will spread the load back along the existing footing, so no need to cast new pad footings.

I doubt you will be able to have a completely flush wall where the kitchen joins the breakfast room; you need to give lateral stability to the flank wall. Maybe you could have a stiffer column near the party wall and something narrower the other end. *Maybe* you could even chase the column partially into the existing wall and bring out the wall flush using insulation boards.

You will get away with smaller beams and end columns if you go for a central column, but you will need a steel in the middle, not a pier. As drawn the central pier wouldn't take the loads.

I think which option you go for is down to finances and personal preference.

 

[geraint]

A steel at that length will end up around 300mm deep, this can be shoehorned into the floor zone above to raise it up at further expense. You'll also need a sizeable column at each end where the hit the external walls, these may require pad foundations. Having two smaller steels and a mid-span column will likely be cheaper. Any decent structural engineer will be able to do some fag packet calcs in about 5mins and give you a steer as to the most suitable solution, goal post solutions included.

until you get a se involved nobody can tell you... and anyone stating a size is immaterial.... as no such thing as a 300mm steel.. is available. so best to ask.

 

[RonnyRaygun]

until you get a se involved nobody can tell you... and anyone stating a size is immaterial.... as no such thing as a 300mm steel.. is available. so best to ask.

He'll have to get an SE involved...although I've designed enough of these to be pretty confident of the sizes.

And Freddy is talking about a 305 UC...not going to argue about 5mm are we??

 

[freddiemercurystwin]

A steel at that length will end up around 300mm deep, this can be shoehorned into the floor zone above to raise it up at further expense. You'll also need a sizeable column at each end where the hit the external walls, these may require pad foundations. Having two smaller steels and a mid-span column will likely be cheaper. Any decent structural engineer will be able to do some fag packet calcs in about 5mins and give you a steer as to the most suitable solution, goal post solutions included.

until you get a se involved nobody can tell you... and anyone stating a size is immaterial.... as no such thing as a 300mm steel.. is available. so best to ask.

1) My post recommended the involvement of an SE did it not?
2) A general rule of thumb for steel beam spans is the depth = 1/20th span, the answer in this case being 285mm. Guess what, a 285 beam of that size does not exist either. 300mm was mentioned as the beam would 'be around' that size.

Idiot

 

[geraint]

until you get a se involved nobody can tell you... and anyone stating a size is immaterial.... as no such thing as a 300mm steel.. is available. so best to ask.

He'll have to get an SE involved...although I've designed enough of these to be pretty confident of the sizes.

And Freddy is talking about a 305 UC...not going to argue about 5mm are we??

someone just stating a size of beam, with no knowledge, can have the opposite effect...

 

[geraint]

A steel at that length will end up around 300mm deep, this can be shoehorned into the floor zone above to raise it up at further expense. You'll also need a sizeable column at each end where the hit the external walls, these may require pad foundations. Having two smaller steels and a mid-span column will likely be cheaper. Any decent structural engineer will be able to do some fag packet calcs in about 5mins and give you a steer as to the most suitable solution, goal post solutions included.

until you get a se involved nobody can tell you... and anyone stating a size is immaterial.... as no such thing as a 300mm steel.. is available. so best to ask.

1) My post recommended the involvement of an SE did it not?
2) A general rule of thumb for steel beam spans is the depth = 1/20th span, the answer in this case being 285mm. Guess what, a 285 beam of that size does not exist either. 300mm was mentioned as the beam would 'be around' that size.

Idiot

general rule of thumb..... you have no knowledge at all about structural steel... your advice and calculations are very dangerous to someone on a forum that might heed your advice..

 

[geraint]

until you get a se involved nobody can tell you... and anyone stating a size is immaterial.... as no such thing as a 300mm steel.. is available. so best to ask.

He'll have to get an SE involved...although I've designed enough of these to be pretty confident of the sizes.

And Freddy is talking about a 305 UC...not going to argue about 5mm are we??

is he going to specify the weight of it or will he just guess to the nearest number.... or what size section.....

 

[freddiemercurystwin]

What calculations? A general rule of thumb is just that and if the OP is to take my advice they will also employ an SE. Have my thoughts not been echoed by RR, himself an SE?

And frankly in anycase I do not give a rats arse about anyone undertaking structural work without Building Regs Approval and subsequent SE involvement.

 

[freddiemercurystwin]

is he going to specify the weight of it or will he just guess to the nearest number.... or what size section.....

Where have I specified a beam size exactly?

 

[geraint]

What calculations? A general rule of thumb is just that and if the OP is to take my advice they will also employ an SE. Have my thoughts not been echoed by RR, himself an SE?

And frankly in anycase I do not give a rats a**e about anyone undertaking structural work with Building Regs Approval and subsequent SE involvement.

how can you give a rule of thumb.... no such thing on a forum... you can only do that when you have seen the situation.. loadings etc.

very dangerous.......and there is no defence..... or quoting rr

 

[geraint]

is he going to specify the weight of it or will he just guess to the nearest number.... or what size section.....

Where have I specified a beam size exactly?

well you cannot as you do not know.... you suggested something but so could i i could also suggest you have brown bread with no butter.... but what do i know about that....

 

[geraint]

What calculations? A general rule of thumb is just that and if the OP is to take my advice they will also employ an SE. Have my thoughts not been echoed by RR, himself an SE?

And frankly in anycase I do not give a rats a**e about anyone undertaking structural work without Building Regs Approval and subsequent SE involvement.

think you should stick to singing..... kareoke tomorrow night....

 

[freddiemercurystwin]

OK ask an SE how they come up with typical beam sizes at the drop of a hat then?

Only someone very naive (or stupid) would take something derived from a rule of thumb on a Forum literally.