Building control query regarding roof purlin

[freddiemercurystwin]

Suggest you stop now and get an SE involved.

 

[Hampshxre]

I am mate

 

[stevie888]

I just take out the chimney which was supporting the purlin and added a full length one to the front of the existing.
Are your saying it will require a steel no matter what?

Thanks for the message

Absolutely not. Far too many loft conversions have loads of unneccessary steel specified.

As an extreme example I was asked to redesign a loft many years ago after 2 builders had refused to price it. The design had actually been approved by the LA though they are never going to say "that's too strong" (they did miss stairs that didn't work but that's another story). 2.5 tonnes of steel with a single piece weighing 750kg!! My design wound up using a single steel of about 45kg, stairs that worked and provided a real wow factor due to the layout of the landing.

In a conventionally built house with a central load bearing wall timbers from that wall going in both directions will usually suffice to provide the basic structure. The purlin is replaced by studwork set immediately behind the it which sit on those timbers which clearly have to be designed to take the point load.Once that studwork (which clearly has to be done accurately so there is no movement) is complete the purlin and any props can be removed. You will sometimes see these studs set under the purlin itself but this is not good practice as there is then a risk of the purlin trying to rotate.

As others have said, you're where you are so it's time to get an SE or probably better an experienced loft conversion designer involved.

 

[Ollyfp]

No and the isualtion is coming out as it needs to be 100 or 150 on top of the roof joists then insualted plasterboard on that

We worked with a 30mm gap between celotex and the vpm (Tyvek) which satisfied building regs.