Loft Conversion: RSJ, Joist Hangers, attaching rsj to Gable

[IanMcD]

Hi,

I want to get cracking on a loft conversion on a bungalow and would like some help in understanding the particulars of the materials I'll be needing.

I have a lot of internal solid walls and plan to place RSJs from the gable to the internal walls and suspend floor joists from them. I understand that to do this I need joist hangers, I've never used a joist hanger, do they differ in sie according to the dimension of the RSJ, and how are they attached to the RSJ?

I also plan to extend supports vertically upwards from the rsj up to the roof joists to support them intead of using the gigantic purlin tha is in place. How are these vertical posts attached down to the RSJ and upwards to the roof joist, is there some specialized bracket involved here?

Finally, what mechanism is used to fix the RSJ itself in place. My house is very long, 54 ft, so I plan to use two lengths of RSK, ie. 2 RSJs on each side of the house. I expect it is sunk into a hole knocked out of the gable on one end and bedded in with concrete, is that correct?

But then when I rest it on the internal solid wall , what is used to hold it in place there?

I understand I'll need to abide by BR , I'll get my architect friend to double check what I'm doing along the way but I'd like these questions answered to help me in planning work,and pricing and ordering materials.

Thanks for helping an adventurous DIYer save 10,000 euros. (in ireland)

Ian

[Brian G]

What size is the RSJ? It is normal to have the RSJ the same height as the timber floor joists and just 'notch' the timber joist so it sits inside the 'web' of the RSJ - ergo joist hangers are not needed

Personally I would not consider replacing the purlin with hangers - bearing in mind the roof will weigh several tons (or tonnes) and you could cause some serious damage to the roof in doing that - if you decide to go ahead, then the section size of the timber hangers must reflect the roof load that will be carried and this additional weight will then also be transferred onto your new RSJs thus increasing the floor loading - remember that you must also take into consideration any winter snow loading.

As a caveat to this, if you intend to fit some sort of a dormer window, then the roof purlin will obviously have to be cut and a method of supporting (trimming) the cut ends worked out to maintain the load carrying integrity.

Near enough.

Bricks cemented to the internal wall on either side of the RSJs - but if can be done in one length, the nothing as the floor joists will hold it.

In view of the questions that you have asked, I would seriously agree with an Architect having a look and advising *before* you start - and possibly a structural engineer as well.

Ian, just take care in what you are doing and take all the professional advice that you can get with regards to roof and floor loading/designs as a 'bad decision' may cost you far more than the 10,000 euros that you are trying to save.

Best of luck on the project,

Brian G

[BigWallop]

What does your structural engineer say about the calculations on this job? What would he / she advise to make it all safe and secure?

[Bod]

What about the extra load of the floor on the existing walls that the RSJ will be sat on, won't u need calcs from engineer?? can you start without planning permission, building regs etc in Ireland? Hope all goes well