RSJ over 5m patio door advice

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hello, newbie here, been reading for a while and thought it would finally be time to post as i have been scratching my head for weeks now. We are about to start our extension, a 6m flatroof rear extension spanning the full width of the bungalow which is just over 7m, so not a huge extension. We have decided to have 5m patio doors on the rear, however we really wanted 2400mm tall doors, and im just having some problems working out how to do this.

As per planning agreements of prior notification, our extension cannot exceed 3m in height. Our inside ceiling height will be 2.5m give or take and its 2.5m from dpc to the eaves of the roof. I have contacted a structural engineer however i cannot seem to get a reply since agreeing on him designing the RSJ.

I have a few questions.

- i will need I joists for this span, but im not sure what size, any advice?
- is it possible to have an RSJ only 100mm in height? It needs to span over the cavity so will be 300mm wide in total, i was hoping to get two RSJs welded together, any advice?
- another option im guessing is to fix the roof joists into the RSJ, then we can order 2500mm tall doors and wont have any issue with RSJ size, what size will I need to support the roof.

The patio doors have no downward pull on the RSJ, it will simply be supporting the flat roof.

I will be doing most of the work myself, im fairly handy andy as im a plasterer, hence why Im asking here rather than paying for an architect or something similar to design the specification

Any advice in regards to this would be much appreciated
 
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I think your RSJ height is far too low. I would think that over 5m unsupported it would sag by at least 1/4" under its own weight. Your tariff for the height is .5m, so 25mm for felt and boarding, how deep is the extension?, at a guess 4m, so 80mm for the slope. Roof joists, 175mm,, this then gives 280, out of your 500. Leaving you with 220mm for the RSJ (about). If you used joist hangers on the RSJ, then you can save the 175 as the depth of the joists are in the depth of the RSJ.
Frank
 
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On that span, the optimium beam would be a 203 x 133 x 25 or 30 UB.
You can bolt timber into the web, and use joist hangers to support the I-joists.
 
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I think your RSJ height is far too low. I would think that over 5m unsupported it would sag by at least 1/4" under its own weight. Your tariff for the height is .5m, so 25mm for felt and boarding, how deep is the extension?, at a guess 4m, so 80mm for the slope. Roof joists, 175mm,, this then gives 280, out of your 500. Leaving you with 220mm for the RSJ (about). If you used joist hangers on the RSJ, then you can save the 175 as the depth of the joists are in the depth of the RSJ.
Frank

On that span, the optimium beam would be a 203 x 133 x 25 or 30 UB.
You can bolt timber into the web, and use joist hangers to support the I-joists.

Awesome!!! Thanks for the info, and yeh makes sense on the measurements, i was going off another flat roof extension I had seen, the measurement to the eaves was 2.5m but by that calculation they hadnt used the full 3m allowance, makes sense now. I take it a 30UB can simply have a plate welded on in order to span the full width of the cavity?
 
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I would have been thinking 152x152UC - 23kg would prob do it but otherwise 30.
 
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And if you want the UC to span the width of the wall & cavity you can have a 10mm steel plate welded to the bottom to give you equal support and a 'shelf' for the external brickwork between the joists if you need it.
 
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Thanks again. Ive actually got a bargain on a set of sunflex/id systems patio doors which are 6.191m wide and 2.248m tall, including the flush track so once thats in will probably be regular height ish. You still think a 30UB will be suffient? Ive still not heard from the structural engineer after chasing him 3 more times and the other prices I got seem rather expensive, what would I be expecting to pay for the beam spec calcs?
 
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Remi how much of a bargain did you get on your patio doors?
 
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Remi how much of a bargain did you get on your patio doors?
I guess because you are implying I cant use them because of the 660 minimum of masonry, i understand I can have a steel goalpost frame, anyone got any rough ideas on price of the steel etc? Also how do these connect to the foundations etc?
 
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No I was genuinely asking how much and where you got then from :)
Ask BC about your masonry returns, they might think it's ok. If you phrase it in a way they might never notice. If they pick up on it they might ask for wind posts (£150 each?), a buttress wall or hollow concrete blocks with rebar. I think steel goalposts would be a bit ott. You should already have a beam calc for the UB so just ask them to see if you need anything on the returns.
 
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No I was genuinely asking how much and where you got then from :)
Ask BC about your masonry returns, they might think it's ok. If you phrase it in a way they might never notice. If they pick up on it they might ask for wind posts (£150 each?), a buttress wall or hollow concrete blocks with rebar. I think steel goalposts would be a bit ott. You should already have a beam calc for the UB so just ask them to see if you need anything on the returns.

They are sunflex 4 panel sliding patio doors, 25mm sightline, they were slightly over budget and bigger than we wanted but they retail at 12k I got them for 4.5k as they were used for 2 exhibitions. There is a local branch of sunflex near me and they post their mismeasures/ex display stuff on ebay and I snapped them up. Now going to google wind posts but the hollow blocks sounds decent to me. I may just ask the neighbour and see if they mind me building to the boundary then will give me the return I need anyway.

guy i emailed for calcs said i need the 665mm return each side and that was it really but said he will email me tomorrow as he was then leaving the office so will see what he says
 
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Just googled buttress wall, the missus likes deep reveals round the windows so I was thinking maybe I could do a double thicknes wall on the outerskin, reckon that will help keep BC happy?
 
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Yes but check first, you may need a 300mm wall
 
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