Extending RSJ?

We have a two storey side house extension completed in the mid 80s with 205 by 205 column used as beam supporting first floor and external cavity end wall above. Beam is needed as first floor is set back, presumably for planning reasons at the time.

The beam is supported on a pier at the one side and on the cavity wall that forms an external store on the other - effectively a 1m "pier" perpendicular to the side external wall. Store is formed in approx 1m by 1m corner of the extension.

I am looking to remove the store to improve the layout, making the currently "lost" corner part of the room.

From a bit of exploration beam is supported on approx 500mm long padstone on 1m "pier" cavity wall. End of beam is approx 500mm from external wall and does not run through as I had hoped. Room width is 3.7m so beam spans 2.7m at present and is circa 3.2m long.

I am thinking through how to do this and would appreciate any advice. Appreciate I'll need to get structural calcs completed and talk to BC but mechanical engineer so relatively familiar and have completed some rough calcs.

Seem to be three options:
1. Remove existing beam and replace with suitable length one, building conventional pier for support.
2. Extend existing beam by welding new section. Approx 600mm length would need to be site welded. Calc shows around 1.5mm deflection with existing beam size. Beam into inner face of cavity wall and conventional pier constructed.
3. Remove 1m pier and replace with steel column with spreader plates to support existing steel and insert lintel for remaining 500mm opening.

Of course there is a fourth to leave it but the missus is not keen on that!

I know all will work but my concern is the practicality of each using a typical domestic builder. Option 1 will be most disruptive. Option 3 limits space use and will require temp beam support while installing column etc. Option 2 seems preferred but is it reasonable to expect that I could get the welding completed to the required standard. All seem a lot of hassle to remove this 1m by 1m waste of space but it will make a big difference to the use of the space.

Views on what others may have done and what would be the most usual way of dealing with this would be appreciated as I'm scratching my head on the best approach. Thanks.

Leave it. Sod the missus.
This will be an extraordinary amount of work and expense just to reclaim 1m² Can't you just rejig the furniture and put the store to good use? Like locking her in it until she comes to her senses

depending on the weight of the existing 203 UC , I would be very surprised if it couldt deal with your needs.

I assume you have a plate welded to the top to carry the width of a cavity wall

It could also be extended by bolting on an extra length with flitch plates, Eng should be able to calculate suitable plates and size/number of bolts.

Jason

Thanks very much guys for the responses. Yep, lots of hassle for minimal space gain but this has a big impact on the layout with my other alternative adding a single storey extension instead. There is a spreading plate on top of the UC but have not yet fully explosed to check it properly supports both leaves of the cavity wall- sure it must do!

Extending the UC seems to be preferred of the options but is this something that is relatively common to do and something that your average domestic builder could cope with, or a very specialist task where I may struggle to find someone willing (or suitably skilled) to do it? Any suggestions of folk in South London/Surrey to try?

I was thinking of welding as getting into drill from above in my eyes would involve more removal of block work above to gain access. But ultimately I'd leave it to whoever I get in to do it to take their choice.

andrewph said:

but is this something that is relatively common to do and something that your average domestic builder could cope with,

Click to expand...

If it was my house , i would definitely go for extending the existing , as mentioned previously , plates and bolts would also be a common solution for the joint , I have heard before that this actually takes a lot of the deflection out of the beam .

A number of loft extensions I have drawn have had the main beams designed in 3 pieces for ease of install .

I am sure most builders would cope with this task in their daily stride .

Thanks all for the advice. Bit more exploration over the holidays and then I'll have to get the calcs done to confirm all OK and should be able to crack on.