Steel Beam support

motorhomer · 21 Aug 2017

I need some advice on the size of steel beam to support a glass roof. I am building a conservatory glass roof 4.5 meters wide by 8.5 meters long. The glass will be 800mm wide supported on 100mm x 100mm beams at 4.5 M long.
I need to put a steel beam as a purling along the 8.5m in the middle of the roof. i will be doing this with two beams supported in the middle by a second cross beam. I have attached a drawing that might help.
I have worked out the weight of the glass will be 30 Kg/m^ and the total weight will be 1080 Kg
Can anyone point me in the right direction to what size steel beam i would require. I have been advised a H beam of 127x76 for the purling and 152x152 for the center cross beam

Mr Chibs · 21 Aug 2017

You could probably need a structural engineer, wouldn't be much to sort this out, could be done via email.

I take it, it's a lean-to?
Is the 30Kg, just the glass?

motorhomer · 21 Aug 2017

Yes this is just the glass. Only from my calculations on line. i will be using toughened units 700mm by 2250mm at 4mm thick. Glass is 10kg per m^ so I work this out to be 30Kg per unit. I will need 24 unit so total across the roof will be 720kg. I have redone the calculations as i have changed to sizes of the units and thickness. i will be speaking to a gazer tomorrow to confirm this can be done.
i agree I could get a structural engineer to do the calculations and I probably will have to but so far I have had quoted of £700 to £1000 for this. At this price i will be thinking about just doing plastic roof or paying a contractor to supply the roof

Mr Chibs · 21 Aug 2017

SE doing roof calcs could be got for less than £200 I would have thought, think I paid similar for vaulted ceiling roof calculations.
PM me, if you need details, he's based in Yorkshire, and yes, the council signed it off.

Also, your panes will be longer than 4.5m room width as when they will be angled, this changes with pitch.

Keep us posted.

motorhomer · 23 Aug 2017

Change in direction I was looking into doing the glazing beams in wood. If they where made from 150mm x 50mm Ash would I still need a purlin. I would need noggins to stop any sideways movement but over a 4.5 M span and at 10 deg would these beams take the weight. Its a very strong wood and has good bending ability with out failure. Also works out similar price to the self supporting bars.

Mr Chibs · 23 Aug 2017

No dis-respect but it sounds like you know the ash will be good enough, so possibly you have your answer.

At over 1000kg, when you factor in wood/glass/fittings etc... only you can be comfortable with knowing if it holds.
What are the sides of this lean-to? yellow line on your pdf.

Who/why advised (initially) on the steel beams?

motorhomer · 23 Aug 2017

Hello Chibs thanks for the comment. The yellow box in the drawing is just highlighting the conservatory boundary, the front will be full glass and the sides are wood stud walls with cladding. I have been told that over 4 M span the glazing bars will need support, but I am just over at 500mm so not sure how much this will affect them. So a still purlin would work but I believe this to also be over the top. If I need to fit a purling it all becomes more complicated as it would be 8.5 M long and the side walls will need strengthening so not ideal.
I still have a few ideas on using wood for the support and a purlin can then be installed with a center V truss

total weight of glass is 720kg but this is over the hole roof. Each beam will only be taking 60kg and I think Ash would easily take this weight, even Red grandis I would expect to take the weight.

I am talking with a friend the weekend how was a builder for over 40 years as a carpenter, they said wood would be fine so I will let you know what I find out.
It would look so much better if made from wood and with no purlin. Purlin would not look bad just more work.

Mr Chibs · 23 Aug 2017

A bit tricky I think.

Deeper wood is stronger than thicker, if I imagine rafters (say 150 x 50) they can take a good combined weight.
Only issue is your front and side walls are not brick, so you'll be reliant on the wall fixings taking the brunt of the weight, and your front wall is going to be glazed.

Is the intention to bolt some wood/metal to the back wall of the house and hang the rafters from this?

I see why you don't want to use a purlin, it will be very long, they can be spliced together though... but you'll only be resting it on a studwork wall.

I'll be interested in what other suggestions you get.

PS. could you save weight using polycarbonate?

Might give you some food for thought.

https://www.ribaproductselector.com/Docs/5/20765/external/COL1520765.pdf

garyo · 23 Aug 2017

motorhomer said:
total weight of glass is 720kg but this is over the hole roof. Each beam will only be taking 60kg and I think Ash would easily take this weight, even Red grandis I would expect to take the weight.

Don't forget the metre of snow...

motorhomer · 23 Aug 2017

The side walls will not be taking any weight unless a purlin was installed in which case I would build brick piers.
The beams will be attached to the house wall on a wall plate and the front will be on a 4 x 4 hard wood plate across the top of the whole front. Each beam will match up with the up vertical bars of the front which is strong enough to take the weight.
My main issue is with the beams across the span taking the weight and not bending which will cause leaks and possible braking of the glass.
I understand the snow weight which can be a lot and the wind will put weight on the roof. This is the main reason for increasing the beam size as 150 x 50 hard wood beams should easily take the weight of two glass units.

I am speaking to a company on friday who supply self supporting bars for glass and will see what they say.
http://www.glazingsystems.co.uk/3-0...-polycarbonate-sheet-available-in-any-colour/

I have also emailed the standard patent glazing company as there web site boast a skyline beam which can go over 7 M with no support needed. link below, however they have not replied to any emails and do not answer the phone

http://www.patent-glazing.com/rafterline-patent-glazing-bars.html

I dont want poly roof as I have this at the moment and it is terrible. Noisy dirty and a lot movement. Ended up paneling over the inside which a lot of people do but then you loose the light

Mr Chibs · 23 Aug 2017

Yes, I know about the purlin, sorry, wasn't clear in my post.

Could you not build both corners and a mid pier (brick/bloack) on the front, then a beam(s) spanning across? or same idea with three metal columns/heavy duty box section?

Out of curiosity with the patent-glazing system and using your new pdf, how is 2nd tier of glazing watertight, do the glazed panels just overlap?

motorhomer · 23 Aug 2017

Thought i would upload pictures of current conservatory. I will be using this front brought forward to the new boundary line. As you can see the current roof has velux openers sitting on the hard wood beams which are easily same weight as glass units if not more and this has been all ok for 6 years.
I am really not worried about the front weight only the span of the beams.
I will let you know what i find out from the company's over the weekend. The guys that do the skyline bars have got back and said they could do it all if I give then some details. Will sort this out tonight and see what they say.
As for the two tier drawing this was done in wood, using there beams I expect I cannot do this and will be back to joining the units. I thought I saw on there web site that they did this so will have to ask them

Mr Chibs · 23 Aug 2017

It's a bit more like a half lantern construction on top of a frame work, with quite a large cross member.
On the area that's not glazed, what is the roof construction?

motorhomer · 23 Aug 2017

Externally this is all poly sheets, internally this was paneled over due to noise. This roof will not be what i am fitting on the new conservatory as it will be all glass.
Construction of the current one is 4 x 4 grandis red hard wood beams with none supporting glazing beams on top.

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