# Forum Home Renovation Structural Renovation  steel or laminated timber beam?

## KAW

Hi 
I am having a 6 panelled stacking sliding door installed with a panel of louvres at each end.  The total length of the doors/window will be 6.2m and 2.1m high.  The actual opening space is around 3.75m. (Louvres FXXXXXF Louvres)  I have had quotes from 2 builders.  Builder #1 suggested a steel support beam 300m high with steel support posts at either end.  Builder #2 has suggested 2 laminated timber beams 240mm deep, 45mm thick, nailed together with no additional support posts.  Obviously the timber option is cheaper, requiring less labour to install.  My questions are which option is structurally the best? and which would you opt for? 
Thanks!

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## Eastwing

I Would use Steel.

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## rod1949

:What he said:  plus you'll never have termites eat the steel out :2thumbsup:

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## jago

3.75m is not that big whats above the opening? 
I have just put in a 6.5 metre wide stacker used a 360UB57 but it had to support two floors and a roof. If you dont have easy access the steel can be a PITA.

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## Stan 101

> 3.75m is not that big whats above the opening? 
> I have just put in a 6.5 metre wide stacker used a 360UB57 but it had to support two floors and a roof. If you dont have easy access the steel can be a PITA.

  You haven't told us the effect floor and roof loads areas you beam is design for so stating a 360UB does not offer assistance. More info is needed. 
The opening is not 3750mm, total length is 6200mm as per the OP's text. The lintel will be carrying the door setup and roof loads and wind loads. 
If the stacker doors aren't fixed at each end of the opening, the lintel will need to be designed for an additional point load for the mass of the doors as they could then be stacked in the centre of the opening. It makes a huge difference to the lintel size. 
Cheers,

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## jago

> You haven't told us the effect floor and roof loads areas you beam is design for so stating a 360UB does not offer assistance. More info is needed. 
> The opening is not 3750mm, total length is 6200mm as per the OP's text. The lintel will be carrying the door setup and roof loads and wind loads. 
> If the stacker doors aren't fixed at each end of the opening, the lintel will need to be designed for an additional point load for the mass of the doors as they could then be stacked in the centre of the opening. It makes a huge difference to the lintel size. 
> Cheers,

  So Stan 101 are you offering advice? 
No more info is required I was offering an example not a opinion of the size of the beam as I don't hold my engineers ticket yet, do you ? :No:  
Whos to say the opening is 6.2 as the doors can be made to hide the steep posts between the fixed panels or louvres you know as little as I Stan. 
back to the OP ...I used a Steel beam beacuse of previous termite damage; with steel the fitting will have to allow for the defelection of the beam under its own weight so if you are running tight on head height the beam will have to be fitted before the door is constructed.   
OP you should consult an egineer as they will run the calcs and certify. :2thumbsup:

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## Stan 101

> No more info is required

  It's unforunte you've taken what seems to be offense to my post. My post might sound harsh,it's simply due to the speed at which I type my responses. I don't give much thought to making them sound inoffensive to all. I certaily don't type them with intension of making them offense either. 
I simply clarified that you have not offered enough simple data. You've stated the beam supplied to your home is carrying roof and floor loads. Without knowing the floor and roof loads the beam size is arbitrary. With all due respect, without offering the the roof and floor loads, the example is useless.    

> 

  now how do you know that? I bet my previous employer's face would be red if I wasn't qualified to comment on such designs.     

> Whos to say the opening is 6.2 as the doors can be made to hide the steep posts between the fixed panels or louvres you know as little as I Stan.

  Well good building practice guided me. The OP has offered no mention of internal supports for the beam. The OP has also not mentioned the roof or roof and floor loads being applied to the lintel and this is critical in this type of design especially if the clear span in the centre of the lintel is 3750mmas you have suggested. 
With an opening of 6200mm the lintel will effectively be clear spanning and will have just simple moments. If however, there are supports creating a span of 3750mm the two other spans could then effectively become cantilevers and the posts/short wall/mullian (I'm assuming) become cantilever supports if the roof and / or floor loads are quite low. Cantilever forces on the internal supports are a whole different beast to a simple internal support. 
If this is the case, then there is also a much greater cost involved in tying down the the ends of the lintel . It could also mean a lot more movement and potential cracking of plaster and glass / door frames. 
The better practice, depending on loads, could be to clear span the lintel the 6200mm and take the extra moments out of play when using the mid span supports. However this would need to be checked against lateral loads from wind as this lintel will also need to withstand wind. If wind load is a comparitively high force, it may be better to cantilever the lintel. 
There is never a simple solution without all the data.  
To the OP, I'd take into account how you intend to fix your stackers. Maybe the supplier could guide you in what product is more suitable for application. Steel however will giove you more control of lintel deflection and help to minimise long term issues with cracking etc. 
cheers,

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## twinny

stan sounds like an engineer!!! more info, more fees, more number crunching, same boolshite!!!  :Doh:

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## barney118

> plus you'll never have termites eat the steel out

  LVL's come with yellow treatment T2 for a few extra bucks.  Definitely  more info needed. The hyspan tables are easy to read, I have 2 lintles  for my truss roof which support a truncated girder truss at 2400 setback  (end hip on the roof). I have a 240x63 spanning 3.4m max and a 300x63  spanning 4.5m max. (now incorporated in the stud wall as I enclosed "the  deck".) 
I assume with an opening of 6.2m there must be a wall/stud somewhere to  give the 6.2 span. Or it is a hip end of roof maybe supported by the  corners (hip's) more info needed. 
Either way I would be concerned about the height you have to play with 2.7m wall height or 2.4 ceiling? 
Again save on cost by going bifold instead of stacker getting more room as build costs will come down and be simpler.

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## Stan 101

> more fees

  Good where do I send my invoice? 
Now as I'm full of bullshite please do be kind enough to tell me where the logic in my above post, relating to the lintel design and thought process, fails. 
I have no problem with people picking holes in my thinking, but I would like it done in a manner other than name calling. IE: Maturely. 
This forum, or so I thought, was for better understanding of building application. I think I've given a reasonably precise outline on the concerns one can have in designing what looks like at first glance to be a simple lintel design. 
When you go and inspect a building that has had a timber lintel, underspeced and in similar circumstances, snapped and found inside the dwelling becuase the person who specced it did not take lateral loads into account, you tend not to be as flippant as others might. 
Cheers,

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## KAW

Thank you for all your replies! I have very little building knowledge but i will try to add further information that may help.  the ceiling is 2.4m high and is only supporting a skillion iron roof.  there will be about 150mm of wall at one end of the doors and 2 mtrs at the other end.  it will under a covered deck.   
I guess I am a bit confused about what to do as the builders have offered such different solutions.

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## barney118

Kaw, assuming you have a house and want to open onto a covered deck, you want to modify where the house section current opening? the skillion roof is over the house or deck? 
If you have a 2.4m ceiling on the house then to get doors in of 2.1m high (including framework around doors?) doesnt leave any room for your options using the steel put forward, unless you intend to redo the whole rear end of house, unless 2400-50mm (top plate in wall)-240mm LVL = 2110mm opening for doors including frame.
Basically where the walls are on either end this opeining will form the post to support the beam need to know how much roof load of house above doors is carrying (end hip,gable,truss or convential roof type?).upper storey or lower of 2 storey? brick walls or weatherboard?.

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## KAW

The skillion roof is continous from the newer part of the house to the end of the deck.  It is a single storey weatherboard house.

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## jago

> I guess I am a bit confused about what to do as the builders have offered such different solutions.

  It comes down to a builder that you feel you can work with and who can provide those all important references....I would ask of the builders that you have already seen ...who has done similar work recently and can you speak to their client.  
Forget the arguments here as we haven't seen the job and are for the most are unqualified to advice on structual specifications; we can only provide examples of what we have done. 
IMHO I would base my decision on Cost, Timeframe, Repore with builder and references. 
Good luck :2thumbsup:

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## barney118

A picture is worth a thousand words. But sounds like the area you want to open you have a height issue to start with starting at 2.4 ceiling (house? end) you are not going to get the height to put a steel beam in?
Sounds like new beam needs to carry 2 lots of roof loads skillion plus house. Reason 1 (steel) may be because house is tile roof (a lot heavier than corragated iron).

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## Metung

Assuming you have a standard timber framed house, I'm guessing you have 2.4 metre ceilings and builder 1 is saying that he will use a steel beam and have a 300mm overhead above the 2.1 metre opening and the steel beam will be incorporated in that overhead which sounds pretty good to me. Steel support posts sound even better. I would be extremely surprised if 300mm didn't provide ample room for a steel beam of a suitable depth to carry the loads required. If the house is not on a concrete slab, I would however be asking how he intendes supporting the steel posts. 
I have some reservations about builder 2's proposal in that 2x45mm beams nailed together means a structural thickness of 90mm and I would be interested in how he intends supporting and fixing them with "with no additional support posts", presuming your existing framing is 90mm thick. I also hope he hasn't forgotten the 10mm allowance for plaster.

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## beeblebrox

Hi all long time lurker first time poster. 
I'm in a similar boat to the op. 
SWMBO wants some internal bifold/multifold doors to go across a 4mtr gap where our new sitting room will be.  So I need a lintel to support the 60-70kg of honeycomb doors across the gap.  It's a truss roof above so there's no other load bearing on it just to support thedoors.   Advice from a builder friend was that I can do a 200x50 F17 hardwood lintel which will be more than plenty for the weight .  But she wants 2340 doors not 2040 and I can't get enough room with 200mm lintel to use these doors.   So my thought is to use steel, like a pfc or rsj but I can't seem to find anywhere where I can verify weather a 100 or 125 pfc will do handle the weight with little or no deflection..   the steel guy I asked says I need to get an engineer to design it...  
Any suggestions?

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## r3nov8or

This might help you http://www.edconsteel.com.au/pdfs/in...el_housing.pdf.  
It would be surpising if any 'steel guy' specified this for you (mine wouldn't).

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