Comparison of GluLam Vs RSJ Vs other?

[d000hg]

We're working on speccing up a GluLam beam as previously discussed, as a 6.5m support beam under a solid wall holding up a roof. Our engineer is being a bit slow to specify size or the load requirements so I was looking at LilleHeden's span tables in the interim to try and get a rough idea on size and cost and weight - the taller the beam is the more work we have to do to get it in properly and getting a head-start on that would be good.

http://www.lilleheden.co.uk/Files/Files/Spændviddetabel/Lilleheden_SpanTable_2019_UK_web.pdf

I was wondering, just how do steels compare to Glulam in terms of strength for this sort of application, in ballpark terms? Of course I've seen reasonable spans when people knock out a ground-floor wall, and seemingly quite small RSJs can support the entire weight of a house over quite large spans.
Not the prettiest option but seemingly more affordable as well? If it saved a few inches head-room that might be worth it.

Then I wondered, are there other options? Plastic, weird hi-tech materials you'd see on Grand Designs, etc?

By the way, what exactly am I looking to get from a structural engineer here? Some specific numbers about deflection limits and so on, or should he actually tell me the size and type of the beam explicitly?

Thanks.

PS: for those following this whole project, the cabin arrived yesterday (the guy had to drive through a flood on his Moffet!) and the SE has approved the design subject to deciding on the beam.
This original design:

Has us removing post P1and adding the beam, with additional 'cripple beams' supporting each end:

 

[d000hg]

I was reading this old thread with interest until it descended into bickering and the OP changed the design, so we never found out:

https://www.diynot.com/diy/threads/6-metre-lintle-rsj-advice-please.264337/

I see GuLam comments "your timberyard will spec for you" but I have spoken with several suppliers and they all demand the SE should. Not sure who to believe

 

[^woody^]

The chances of my "timberyard" being able to glue up a beam are the same as them stocking some straight 4x2. Nil.

 

[d000hg]

The chances of my "timberyard" being able to glue up a beam are the same as them stocking some straight 4x2. Nil.

Ha. I hadn't heard them say they'd make them, but I'd seen comments when I searched these forums that they could specify them. I think that might just be people saying things that aren't correct though.

I did read here somewhere about a guy making his own GluLam on site but I have enough going on!

Lilleheden's guy was very helpful on the phone just now, but was clear they would only do specification for larger commercial orders, which makes sense.

They have this fun tool: http://www.lilleheden.co.uk/beamcalc
But I don't know how to use it. I am curious what numbers are needed from the engineer which you could give the beam/RSJ company from which to spec.

 

[Notch7]

I used to but glulams from this company:

http://glulambeams.co.uk/

there is a basic span table on their webiste -I used to use it as a guide, design the structure then get my structural engineer to do the calcs.

I cant see a glulam supplier providing any calcs -they are importers and suppliers and just supply what the customer wants.

for an orangery, I used mostly 405 x 90 section -but the ends were cut down to 315 x 90 for the common flat roof area, the taller part used at the lantern upstand.

Id be surprised if the beam would be less than 315 x 90 or 360 x 90 -Ive no idea if there is any loading on the beam above

 

[d000hg]

Cheers @Notch7. I think it depends if you buy from an importer, or an engineering company - e.g I've spoken to Lilleheden and Donaldsons who can/will do calculations but not necessarily for small orders.

Somehow in all my Googling I'd not found "GlulamBeams.co.uk" which is bizarre. They have a nice selection and use the slightly higher grade C30 too. How did they deliver when you used them... did they have a Moffett or something to get it on site?

The beam obviously has some loading from the stacked logs above but that will be comparable to the weight of the beam (~200kg?). It is transferring roof load which I have no idea about but I can tell you our calculations show under 25kN load down through the wall at each end, it's one of the few things in the calculations I can understand!

We just got a provisional request for the SE to check 405x90 from one supplier. That's going to eat into head-room a bit, a span table suggests 360x115 would be nearly identical but going beyond 115 wide seems to make less difference. I'd really love if we could get 360 or less.

 

[d000hg]

I was wondering how the relationship between strength and area and shape of beam work. Clearly a 10"x1" board functions hugely differently than a 1"x10" board

I was playing with the online tool http://www.lilleheden.co.uk/beamcalc wondering if I went with TWO 90mm wide GluLams, how far down I might push height to get the required properties of a 90x405. Clearly it's getting into diminishing returns but a couple of inches with a low-ish beam is a big deal. It would also be a lot easier to get the damn things in place because ~170kg is a big lift without a crane, and I don't want to try and get a crane on site! It's only 7' off the floor so in theory taller workmen could do it without platforms but you'd want what, half a dozen strong lads for that.

Don't worry these questions are going to the engineer but he'll be done for the day now and the idea of two thin beams in parallel struck me as interesting:
- if 90x405 is enough, then 180x???
- are two 90x??? beams side by side actually equivalent to 1 180x??? anyway if they get bolted together?

If anyone has any idea how to convert between GluLam and RSJ I'd still be interested.

 

[tony1851]

Why not just use a steel beam instead of all this faffing about. I don't know your loading or span but a steel beam will outperform glulam any day in terms of strength, depth, deflection and cost.

 

[d000hg]

Why not just use a steel beam instead of all this faffing about. I don't know your loading or span but a steel beam will outperform glulam any day in terms of strength, depth, deflection and cost.

Well you'll see that's what this thread was asking... I'd assumed this was the case but have no idea how the two compare.
How would comparable wood/steel beams compare in terms of weight, any ideas? Because my concerns for this project would be size, weight, aesthetics and cost.
It's an internal, visible beam so glulam has a benefit you can make a feature of it. But that's not a deal breaker if a steel is smaller and can be clad or polished or whatever

I did briefly look into aluminium but maybe that's crazy talk!

 

[John D v2.0]

if you're worried about the weight and how to install it, it might turn out to be safer to make a composite beam from a couple of large timbers with a steel plate sandwiched between. But ideally an experienced SE would listen to your requirements and design the best solution possible while keeping the cost to a minimum.

 

[Nozzle]

Why not just use a steel beam instead of all this faffing about. I don't know your loading or span but a steel beam will outperform glulam any day in terms of strength, depth, deflection and cost.

A steel beam needs (?) to be boxed in for fire protection, a glulam does not. Glulam also looks a whole bunch better. This was the argument put to me by a previous architect anyway. Obviously the timber beam still burns whereas the steel does not - but the steel beam will bend before an equivalent glulam is burned through.

Nozzle

 

[d000hg]

if you're worried about the weight and how to install it, it might turn out to be safer to make a composite beam from a couple of large timbers with a steel plate sandwiched between. But ideally an experienced SE would listen to your requirements and design the best solution possible while keeping the cost to a minimum.

I'd be concerned it's getting more complicated but maybe it isn't really. Interesting idea, thanks.

A steel beam needs (?) to be boxed in for fire protection, a glulam does not. Glulam also looks a whole bunch better. This was the argument put to me by a previous architect anyway. Obviously the timber beam still burns whereas the steel does not - but the steel beam will bend before an equivalent glulam is burned through.

Nozzle

from what I gather it would only be required if it impacts on safety to exit the building, fire regs are a lot more grounded in common sense than I'd been worried about. In a building that's essentially a single room a fire will not grow to the point it's consuming the building before everyone can leave. Even if did, there's nowhere to hide; by the time a steel beam is hot enough to bend you are dead.
If as in our case, there are no other buildings, it seems building control are not concerned about the building surviving, only about it surviving long enough to get out safely! For small buildings particularly the rules are fairly straightforward (from what I'm told, but we're working with BC on this right now).

We've probably all been in buildings with exposed steels, it's quite trendy these days. But that might be in buildings with active suppression which could change everything? We're on a bit of a tangent now though!

 

[tony1851]

A steel beam needs (?) to be boxed in for fire protection, a glulam does not. Glulam also looks a whole bunch better. This was the argument put to me by a previous architect anyway. Obviously the timber beam still burns whereas the steel does not - but the steel beam will bend before an equivalent glulam is burned through.

Nozzle

As it is supporting a roof, it does not need to have any fire resistance.

 

[tony1851]

Well you'll see that's what this thread was asking... I'd assumed this was the case but have no idea how the two compare.
How would comparable wood/steel beams compare in terms of weight, any ideas?

To evaluate that, someone would need to work out the size of timber and steel beam needed, which in terms of time required is a big ask!

 

[d000hg]

To evaluate that, someone would need to work out the size of timber and steel beam needed, which in terms of time required is a big ask!

No rule of thumb or guesstimates?

I said above that one company reckoned a 90x405mm glulam was required based on 6.4m span, 6.0m unsupported. I'd happy entertain educated guesses from people with some experience what approximate RSJ might be equivalent.

If I can get my SE to verify, you could win bragging rights