Loft steel undersized?

[gasbusters]

Hi, hoping someone can advise. The loft beams my SE has advised off are

203x203x46kg x 5.9 meters.

I made a small cross sectional template as as a guide to start marking out where bricks will be removed. Having made the template the beams "look" too small.

Im not a structural engineer but those beams look too shallow. Can someone advise if those will be an adequate size for a loft conversion? The new floor area will be 5.8 meters x 5 meters, partitioned into 2 small rooms and a small shower room.

 

[wwwebber]

On what basis do you think they look too shallow ? what are you comparing them too ?

 

[gasbusters]

On what basis do you think they look too shallow ? what are you comparing them too ?

Im not sure really, just the height of them, 20cm, does not seem that big and as ive never worked with steel before just thought it looked small

 

[Ian H]

My similar length ridge beam is smaller and lighter, it’s a 203x133x (I think) 28kg.

I’m clueless about the loads on it though.

 

[Notch7]

Im not sure really, just the height of them, 20cm, does not seem that big and as ive never worked with steel before just thought it looked small

Its a universal column section -often specified by engineers when trying to keep beam height down a bit.

It is a pretty substantial beam -weighing 270kgs

Ive no idea about loading, maybe Tony might be along to comment......

 

[Biggles..]

@gasbusters are you end plate and bolting that in or trying to put 6m beams in, in one piece?

That’s going to be heavy.

We put a 152x152x37, 254x146x31 and a 152x89x16 to create our floor.

Then a 178x102x19 for part of the original roof.

 

[gasbusters]

@gasbusters are you end plate and bolting that in or trying to put 6m beams in, in one piece?

That’s going to be heavy.

View attachment 162609 We put a 152x152x37, 254x146x31 and a 152x89x16 to create our floor.

Then a 178x102x19 for part of the original roof.

My house is mid terrace so would be a nightmare trying to get full beams in, The 2 x 6 meter beams will be 203x203x46kg, we are getting each beam spliced into 3 peices, each peice roughly 2 meters long. They will be bolted together with 36 bolts and web plates.

A mate who works at a car parts manufacturing place is a welder, he says once in situ he will run a couple of welds along the web plates to make it even more secure.

Just waiting now for SE to confirm if we can use web plates instead of padstones, been doing some reading online and surprisedvto finf web plates, instead of padstones, are now used quite often. Wonder why SE didnt offer that option in the first place?! Would make life a lot easier!

Thats pic of beam joint details from SE

 

[Biggles..]

You sure you can put them in as 3 pieces? We were only allowed to do it as 2/3-1/3.

Our original drawing mentioned a spreader plate if we couldn’t get a full brick under the beam, 100x450x18.
It was far easier to chop out brick up (all chopping out and bricking up was done from above)

 

[gasbusters]

You sure you can put them in as 3 pieces? We were only allowed to do it as 2/3-1/3.

Our original drawing mentioned a spreader plate if we couldn’t get a full brick under the beam, 100x450x18.
It was far easier to chop out brick up (all chopping out and bricking up was done from above)

The place that supplies the steels say we can do it in 3 equal peices, wecould have done it in 2 but they said the joint cannot be in the middle so one peice would have to be 2/3 of the length which would make it very difficult to get up into the loft (weight would be about 190kg ), therefore they recommended it spliced into 3.

We really want to avoid anything below the ceiling as we spent a lot of time and money decorating the rooms, it would mean 3 bedrooms (wallpapered) and bathroom needing redecorating. I wouldnt be bothered but its the missus, shes very particular when it comes to decor

 

[Biggles..]

The place that supplies the steels say we can do it in 3 equal peices, wecould have done it in 2 but they said the joint cannot be in the middle so one peice would have to be 2/3 of the length which would make it very difficult to get up into the loft (weight would be about 190kg ), therefore they recommended it spliced into 3.

We really want to avoid anything below the ceiling as we spent a lot of time and money decorating the rooms, it would mean 3 bedrooms (wallpapered) and bathroom needing redecorating. I wouldnt be bothered but its the missus, shes very particular when it comes to decor

I wouldn’t listen to the place that supplies the steel, if your doing it in 3, then your SE will need to be the one that says yes/no, it’ll have to go on his drawings and calcs. LABC won’t accept “the man behind the counter says it’s ok”

 

[Leofric]

Yes , the structural engineer on the job is the one who will know the loadings and other relevant information and should be the person to answer all the structural queries .

 

[tony1851]

A 203 x 203 x 46 spanning 5.9m in a loft would be fine.

Regardless of what the steel fabricator says, you can have the splice(s) anywhere you want, including in the middle. The point is that a splice has to be specifically designed with regard to the number of bolts; a splice at midpoint, where the bending stress is greatest, will need more bolts than a splice at third- or quarter points.

One small but important point; your SE has correctly specified HSFG (High-strength friction-grip) bolts for the splice. Make sure that the fabricator gives you these, rather than ordinary bolts. The difference is that the HSFG bolts can be torqued up much tighter than ordinary bolts to the point where they clamp the plates and beam tightly together by frictional force. Ordinary bolts can't do this, and if you use them the beam will bend excessively - see attached pic where the bolts supplied were wrong and a gap has opened up at the bottom plate.

 

[gasbusters]

A 203 x 203 x 46 spanning 5.9m in a loft would be fine.

Regardless of what the steel fabricator says, you can have the splice(s) anywhere you want, including in the middle. The point is that a splice has to be specifically designed with regard to the number of bolts; a splice at midpoint, where the bending stress is greatest, will need more bolts than a splice at third- or quarter points.

One small but important point; your SE has correctly specified HSFG (High-strength friction-grip) bolts for the splice. Make sure that the fabricator gives you these, rather than ordinary bolts. The difference is that the HSFG bolts can be torqued up much tighter than ordinary bolts to the point where they clamp the plates and beam tightly together by frictional force. Ordinary bolts can't do this, and if you use them the beam will bend excessively - see attached pic where the bolts supplied were wrong and a gap has opened up at the bottom plate.View attachment 162650

Thanks for the reply, much appreciated. In regards to tighting up the HSFG bolts, how tight should you get them? is there a special tool that allows you to set the torque?

Also one more question, in regards to the padstones for these beams, I was looking to use steel plates instead of padstones due to thesize specified by my SE which were250x10x215. This would mean going below ceiling level in the bedroom below which we want to avoid.

Are steel plates as an alternative to padstones as effective? I was think of using steel plates that are 450 wide, and 100mm, 30mm thick and 100mm wide.

 

[tony1851]

HSFG bolts usually come with 'load-indicating' washers with little pips on them. As the bolt is tightened, the pips gradually squash up and when the gap is a quoted particular amount (checked with a feeler guage), the maximum torque has been applied. Some types just state a maximum torque, in which case you'd need to get hold of a torque wrench.
It's also important that the mating surfaces of the beam and plates are not painted, as this reduces the available frictional force.

https://www.steelo.co.uk/blog/2018/09/17/hsfg-bolts/

Thick steel plates can be used as padstones instead of concrete.

 

[John D v2.0]

In regards to tighting up the HSFG bolts, how tight should you get them? is there a special tool that allows you to set the torque?

I see tony already replied while I was off learning, but to add to that I found this reference was also interesting: https://www.steelconstruction.info/Preloaded_bolting