Problem With Roof Load onto Steels in loft conversion

[eglwysman]

Hi All,

New to this forum but have posted on others in the hope someone can help. We have done everything right got plans drawn up sent them to an S.E who is a personal friend of our builder. We got a 4 sheet breakdown showing what size steels we needed etc and 9x2 joists to be used great, We ordered everything and the steels are arriving thursday.

However as you can see from the picture below we have got these timber trusses that we will need to remove, Our plan was to have smaller off cuts of 9x2 going direct from the steel upto the rafters at 400mm spaces. The steels are to be placed 3" above the binder and are going to be in between the wall plate and binder, We were also putting collars I think they are called across the top but these would be quite high in the roof as we need the head height, As the room was going to be only one complete bedroom our builder suggested putting in a stud half way in the loft going from the purlins directly down to the new floor but would leave a 10ft opening so still a nice following space from one end to the other. THe problem I got now though is the S.E has stated today (Retired S.E doing this for a bit of extra cash) the calcs he has given for the steels only allow for the floor load and not the roof so he stated we would need to replace the purlins with steels making a total of 4 steels for a velux loft conversion which seem's excessive to me but I am a bit annoyed that he did not calc the steels to take both the floor load and roof and wondered if someone can have a look and help.

This second image shows what we wanted to do putting in the stud wall

 

[^woody^]

The SE is a complete idiot and has effectively scammed you out of any money you paid him. You can't alter the loading without it all being recalculated

Get a proper SE involved who will work it all out

 

[freddiemercurystwin]

Whenever I have done a loft conversion I have used two steels, one each beneath each existing lower purlin and beefed up the rafters so that they can span between the lower purlin and the ridge. The steels taking the load of the floor and the roof.

The SE sounds like a muppet, if he is retired you my want to ask if his insurance is valid?

 

[eglwysman]

Cheers guys for the swift response how you stated you did loft conversions was how I thought however as he has only calculated the floor load it's a bit late to call another SE in to redo it all as we ordered the steels based on these calcs and they are arriving on Thursday costing just under £1000.

So really our only option is to get calcs for two addion steels alongside those pulins at mid point in the roof?

What I will say if their is a poss solution is that where the timber rafters meet the binders directly underneath the binders at those points their is not an internal wall so the weight being placed on the binders surely can't be that much? If we were at mid way in the loft to attach 9x2 joists to those binders and straight upto the purlin at mid point woudl that effectly do what those timber trusses are doing right now and still placed small supports off the steels upto the roof rafters and collars across the top.

Something like this

 

[^woody^]

But isn't your new proposal putting an extra point load onto the floor ... and the beams supporting the floor?

 

[eglwysman]

But isn't your new proposal putting an extra point load onto the floor ... and the beams supporting the floor?

Yes it would, The part of of the stud that goes from the purlin down will go to the binder not the new floor, As they are connected to the binder at the moment which means the binder must be taking part weight of the roof

 

[Static]

Unfortunately my firewall is blocking any photos (probably imageshack or something) anyways but from description you really should be going back to your SE with your plans as any additional loading on the design beams may overload them and without his ok you have no come back.. I would also check his PI insurance cover for this work as said above..
It would be worth asking your SE how he saw the roof supported within his scheme, if he intended for extra steels at purlin level then he should have provided plans and calcs in the first instance and within his original fee (unless he has it in writting he is designing only the floor beams then what £50 per beam)

 

[eglwysman]

Unfortunately my firewall is blocking any photos (probably imageshack or something) anyways but from description you really should be going back to your SE with your plans as any additional loading on the design beams may overload them and without his ok you have no come back.. I would also check his PI insurance cover for this work as said above..
It would be worth asking your SE how he saw the roof supported within his scheme, if he intended for extra steels at purlin level then he should have provided plans and calcs in the first instance and within his original fee (unless he has it in writting he is designing only the floor beams then what £50 per beam)

£50 per beam if it is only that I got no problem, I just paid nearly £1000 for our floor steels, but unsure what size steels I would need of the roof. I went back to the the SE who stated the steels he calculated are for the floor load only so I guess that's a no no.

 

[freddiemercurystwin]

Out of interest what is the serial size of the beams he has specified and what is the span?

 

[eglwysman]

Out of interest what is the serial size of the beams he has specified and what is the span?

I can scan and put them on here or email them to you but I will have a go.

Span is 4m
6.6m between walls
steel size is 8.5" depth (I think)

I will scan the documents and put them up as I don't know what i'm looking at really.

 

[Static]

£1000 is alot for structural calcs.. unless you are refering to calcs and steel cost.. chances are your steels alone at 6m long are around £400 each

 

[eglwysman]

£1000 is alot for structural calcs.. unless you are refering to calcs and steel cost.. chances are your steels alone at 6m long are around £400 each

£1000 was the cost of the steels, The calcs were £250 I hope the steels for the roof are not as much as £400 each as they are only carrying the weight of part of the roof.

 

[Static]

Ok managed to view your calcs on a mobile device.. the first statement on calcs is ridiculous.. not sure how you can have a converted space without modifications to roof trusses unless he was told the trusses would remain as features.. who appointed the SE? If the builder gave bad instructions to him it should fall to the builder to rectify (pay for extra design)..

 

[eglwysman]

Ok managed to view your calcs on a mobile device.. the first statement on calcs is ridiculous.. not sure how you can have a converted space without modifications to roof trusses unless he was told the trusses would remain as features.. who appointed the SE? If the builder gave bad instructions to him it should fall to the builder to rectify (pay for extra design)..

Yes the builder got him for us he is a personal friend of his, I am annoyed as the steels are arriving tomorrow so their is no way to change them so just need someone now to maybe tell me what size steels I will get away with to support the roof alongside the purlin or if their is another way as I have to install the steels we got coming now according to the plans.

 

[eglwysman]

Right we are going to pack up from the internal walls and have stud walls meeting the centre purlin and 3 different parts of the loft that along with short timebrs going direct from the steels upto the lower purlin and collars across the ridge shold quite easy take any addional weight once those trusses are removed.