Anyone good with beams?

[audi321]

Hi all. Planning my summerhouse project and I think I'm going to put a steel beam over the opening for the doors rather than wood.

I haven't a clue what size gauge etc to buy. So does anyone know what kind of load a 5m parallel flange beam (100x50mm) would carry? Something like this

It probably overkill for a lightweight wood/rubber roof, so I'm sure it'll be fine, but I'm starting from a point of not having a clue.

[uk66fastback]

That’ll be more than adequate I’m sure - what length? 2000-2400mm?

What is the flat area of the summer house roof?

[smokey mow]

audi321 said:

Hi all. Planning my summerhouse project and I think I'm going to put a steel beam over the opening for the doors rather than wood.

I haven't a clue what size gauge etc to buy. So does anyone know what kind of load a 5m parallel flange beam (100x50mm) would carry? Something like this

It probably overkill for a lightweight wood/rubber roof, so I'm sure it'll be fine, but I'm starting from a point of not having a clue.

It’s the imposed load rather than the dead load that you really need to consider. The roof may not weigh much but a foot of snow in the winter certainly does.

What mid span deflection are you looking to achieve?
What is the joist/rafter span onto the beam?
What’s your bearing length and construction?

[audi321]

The beam would be 5m (opening is 4.7m - 150mm overlap each side)

The total sq/m of the roof (made of OSB and rubber topped) is about 30sq/m.

[Grumbly]

Nothing 100mm deep will be stiff enough to carry any sort of load on a 5m span,. Just look at how much the stock lengths sag when lifted. A 150x90 pfc may be adequate depending on the roof span.

[audi321]

Yeah I thought a universal I beam might be better. They seem to come in 127 or 152mm depths.

[Chumley.mouse]

8x2. And double them up where necessary…… if its a flat roof you may still get a bit of sag. As a rule of thumb an inch per 500mm.

[Grumbly]

audi321 said:

Yeah I thought a universal I beam might be better. They seem to come in 127 or 152mm depths.

PFCs are significantly stiffer than equivalently sized UBs

[bristolbaron]

Ive been watching a load of summerhouse videos recently due to starting my own soon, and have seen flitch beams as a common option, with others box profile. All have shown 300mm each side rather than your 300mm total though.

With a 5m+ span I’d be looking for professional advise rather than forum opinion, that could go horribly wrong if it all collapsed!

[uk66fastback]

5m is quite a span - and 150mm each side is not a lot. We had a conservatory extension two years ago, and I’ll find some pics. The span was only 3m. The lintel I remember as being considerable. And the flat roof sqm is about the same as yours.

[OutInTheShed]

The fundamentals of beams include:
Material properties
Loads
Allowed deflection
Design.

The roof of a summerhouse doesn't need to support much load. Wind loads could be significant.
Any beam will bend, under its own weight, the weight of what it's supporting, wind etc etc.
How much deflection is acceptable? That might range from a mm to a cm?
Obviously there comes a point where structures move from flexing to failing....
If you're wanting multifold doors to shut, you'll not be wanting much movement. More so if you want to get them open again :-)

Design,
You could make a 5m span building with very skinny structure if it was an arch, Think Nissen hut or polytunnel.
Changing your roof style might make things easier?
A post down the middle of the opening changes things hugely.
Maybe the doors are part of the structure on windy days?


If building regs apply, then some limits have been decided for you.

[Grumbly]

bristolbaron said:

Ive been watching a load of summerhouse videos recently due to starting my own soon, and have seen flitch beams as a common option, with others box profile. All have shown 300mm each side rather than your 300mm total though.

With a 5m+ span I’d be looking for professional advise rather than forum opinion, that could go horribly wrong if it all collapsed!

A flitch beam is a good option with timber framed construction. The amount of retrospective design work I have do where the the beam size has been guessed is depressing, much easier to seek advice before construction.

[smokey mow]

audi321 said:

Yeah I thought a universal I beam might be better. They seem to come in 127 or 152mm depths.

A quick Calc and both would fail in deflection, we’d need a lot more detail to size it accurately but for a 5m span it appears a 178x102 UB would be the minimum.

You then need to consider the bearing and pad stone design.

I’d suggest employing a structural engineer to not just design a beam but also look at the overall design and stability of what you’re proposing.

[audi321]

smokey mow said:

audi321 said:

Yeah I thought a universal I beam might be better. They seem to come in 127 or 152mm depths.

A quick Calc and both would fail in deflection, we’d need a lot more detail to size it accurately but for a 5m span it appears a 178x102 UB would be the minimum.

You then need to consider the bearing and pad stone design.

I’d suggest employing a structural engineer to not just design a beam but also look at the overall design and stability of what you’re proposing.

Appreciate the comment, could you share these 'quick calcs'?

[smokey mow]

audi321 said:

smokey mow said:

audi321 said:

Yeah I thought a universal I beam might be better. They seem to come in 127 or 152mm depths.

A quick Calc and both would fail in deflection, we’d need a lot more detail to size it accurately but for a 5m span it appears a 178x102 UB would be the minimum.

You then need to consider the bearing and pad stone design.

I’d suggest employing a structural engineer to not just design a beam but also look at the overall design and stability of what you’re proposing.

Appreciate the comment, could you share these 'quick calcs'?

Sorry no. I’m happy to guide you but for anything further you need to speak to an engineer.

[essayer]

Just put the biggest beam you can find on -