Structural calculations

[Mike_82]

Hello all,

We’ve recently had a single story rear extension completed and at the time I didn’t give much thought but now it’s playing on my mind a bit.

The opening at the back of the house ended up being approximately 40cm shorter than the intended plans and calculations so our builder obviously used a shorter beam which I noticed was bolted together in the middle.

Should there have been new calculations due to the shorter opening and have you ever come across two RSJ’s being joined like this?

Many thanks,
Mike

 

[Notch7]

Beams can be bolted, although I always go back to the SE before doing. Actually one engineer we use often includes the details for joining in his spec anyway on long beams.

Unless the design has changed in anyway 40cm shouldnt be a prob. The best thing is always to email the SE with the alterations marked and say 'is this ok'.

 

[^woody^]

It's completely different now with a join, and new calculations should be done.

 

[John D v2.0]

Shorter will be fine as they can assume longer fit a worse case, but all structural connections should be designed by the se otherwise how can you know that it's safe. The se has to design something buildable so they should include the necessary connections

 

[Mike_82]

Thanks for the advise everybody.

At this stage, do you think it’s best to go back to the SE advising what the builder has done and get their thoughts on the matter?

 

[Dereekoo]

OK so its a shorter beam but did the longer beam have a joint in the middle, did you ever look at the original proposal?

 

[Notch7]

Thanks for the advise everybody.

At this stage, do you think it’s best to go back to the SE advising what the builder has done and get their thoughts on the matter?

Yes.

You need confirmation the splice is correct.

At the moment the work doesnt comply with the SE spec so he wont be guaranteeing his calcs

 

[Mike_82]

OK so its a shorter beam but did the longer beam have a joint in the middle, did you ever look at the original proposal?

Yes, the original didn’t have a joint in the middle.

 

[Mike_82]

Yes.

You need confirmation the splice is correct.

At the moment the work doesnt comply with the SE spec so he wont be guaranteeing his calcs

Thank you for the advise

 

[Ian H]

Yes, the original didn’t have a joint in the middle.

How wide is the opening? Seems odd to have a shorter beam with a joint rather than a longer one without.

 

[Notch7]

Thank you for the advise

I expect your builder did it for convenience due to access, but its likely he is pretty experienced and has done similar before and used the correct splice plates and bolts. Builders that have been in the game a long time deal with steel connections all, the time and he probably didnt think about it much, just got on with it.

For peace of mind just get it checked out.

 

[John D v2.0]

I expect your builder did it for convenience due to access, but its likely he is pretty experienced and has done similar before and used the correct splice plates and bolts. Builders that have been in the game a long time deal with steel connections all, the time and he probably didnt think about it much, just got on with it.

For peace of mind just get it checked out.

I doubt even with the correct bolts the strength in tension of 2 bolts part way up the web would be as much as the bottom flange.

Just because a builder has installed steels before doesn't mean whatever they did last time is suitable, otherwise why bother with an se at all

 

[Mike_82]

How wide is the opening? Seems odd to have a shorter beam with a joint rather than a longer one without.

About 4m

 

[Mike_82]

I expect your builder did it for convenience due to access, but its likely he is pretty experienced and has done similar before and used the correct splice plates and bolts. Builders that have been in the game a long time deal with steel connections all, the time and he probably didnt think about it much, just got on with it.

For peace of mind just get it checked out.

We used him about 5 years ago to take out a load bearing wall so expected to have no issues again but it only crossed my mind when I was looking through old pictures of the build

 

[Mike_82]

I doubt even with the correct bolts the strength in tension of 2 bolts part way up the web would be as much as the bottom flange.

Just because a builder has installed steels before doesn't mean whatever they did last time is suitable, otherwise why bother with an se at all

That’s what I was thinking.