DIY loft - purlins supporting floor (Edited: Loft Conversion)

[Starfox1892]

Hi,
I want to know your thoughts on this please. We spoke to our joiner a friend of ours) before this work and were reassured it is perfectly fine.

We're in the UK. We're doing our loft with the help of a joiner, roofer and electrician.

Our house is 130 years old and our roof is supported by 4 12x6 purlin beams. We have a load bearing wall that goes right down the centre of the loft, parallel with the purlin beams. Loft floor is 16ft x 16ft.

The joiner couldn't reach the exterior front and back walls due to the lack of space and inability to reach without coming through the ceiling (the old ceiling joists were bowed and weak and have since been screwed to the new floor frame for stability). He fitted vertical 6 x 2 batons onto the purlin beams (8 of these on each side of the loft) and hung the floor frame off those. All of this held together with nails, I have since reinforced the vertical batons with M10 coach screws with washers into the purlin beam and also the beam the floor joists are hung from.

All thoughts welcome on whether this will be sufficient for the load of a spare bedroom or if there's anything else we need to consider.

 

[RandomGrinch]

Have you contacted building control yet?
They may have an opinion on the matter.

Although a little outdated, I have found this document useful when considering the many factors to be taken into account when creating a legitimate loft conversion, that will be a habitable space...

 

[JohnD]

We're in the UK. We're doing our loft

Do you mean you are converting a loft into a habitable room?

Are you in England?

 

[Starfox1892]

Yes into a spare space that will house a bed and yes we are in England.

Structurally, I've been reassured by the joiner who obviously knows far more than me but I've just never seen this approach before. Saying that, I've not seen many loft do ups before so this may be one way of doing it.

 

[Starfox1892]

Have you contacted building control yet?
They may have an opinion on the matter.

Although a little outdated, I have found this document useful when considering the many factors to be taken into account when creating a legitimate loft conversion, that will be a habitable space...

Thanks, I am looking in this anyway. Just wanted to check if anyone has any concerns about the approach used to fit our floor frame.

 

[Dereekoo]

Well the purlins are there originally to support the rafters which would otherwise would have been be to long to take the load of the roof and the purlin would have been sized to take the amount of roof load thus imparted on it. Now you have imparted extra loads on the purlin by suspending your loft floor off it. The question is how much extra load and is this detrimental to the structural capability of the purlin. In all probability because of the inherent safety factors incorporated in structural timber design and the snow roof loading that is unlikely to ever occur (although it could) it will be OK but would not pass a rigid structural analysis using current design codes. As we say in the UK (northern) "Yer pays yer money and yer takes yer chance.

 

[freddiemercurystwin]

Building Contriol will expect a structural engineered solution backed up with calculations not some cobblers a joiner has thrown together. Suggest you put a hard stop on all works until you have the aforementioned.

 

[Starfox1892]

Well the purlins are there originally to support the rafters which would otherwise would have been be to long to take the load of the roof and the purlin would have been sized to take the amount of roof load thus imparted on it. Now you have imparted extra loads on the purlin by suspending your loft floor off it. The question is how much extra load and is this detrimental to the structural capability of the purlin. In all probability because of the inherent safety factors incorporated in structural timber design and the snow roof loading that is unlikely to ever occur (although it could) it will be OK but would not pass a rigid structural analysis using current design codes. As we say in the UK (northern) "Yer pays yer money and yer takes yer chance.

Thanks. There are many DIY loft projects done in the UK without structural engineers and architects involved and this would fall into that bracket. Does everyone who has work done on their loft know the ins and outs of what they're doing if they're getting tradespeople to do the work? No. I do take the point that these beams are meant to support the roof and not the floor and so should be used as such but the work wouldn't have been done in such a manner if it weren't safe.

 

[RandomGrinch]

There are many DIY loft projects done in the UK without structural engineers and architects involved and this would fall into that bracket

That's true, but for you to have a loft conversion that is a habitable space, building control must be involved.
The argument then is, will building control accept the work that has been done.
We may give you opinions from our experience, but the final say is down to them.

 

[freddiemercurystwin]

Thanks. There are many DIY loft projects done in the UK without structural engineers and architects involved and this would fall into that bracket. Does everyone who has work done on their loft know the ins and outs of what they're doing if they're getting tradespeople to do the work? No. I do take the point that these beams are meant to support the roof and not the floor and so should be used as such but the work wouldn't have been done in such a manner if it weren't safe.

Absolutely clueless, don't forget to not bother to renew your house insurance as that's completely invalid now and don't tell the mortgage company either. Your joiner 'friend' is no friend.

If/when the **** hits the fan he'll be all I'm just a humble joiner I don't know what I'm doing.

 

[JohnD]

Thanks. There are many DIY loft projects done in the UK without structural engineers and architects involved and this would fall into that bracket.

Do you think that one day you might want to sell the house? Or remortage it? Or take Equity Release in your old age?

 

[Deleted member 174758]

I do take the point that these beams are meant to support the roof and not the floor and so should be used as such but the work wouldn't have been done in such a manner if it weren't safe.

There are cowboys out there who don't give a damn about whether or not their work is either competent or safe. In addition there are the guys who don't know how limited their knowledge or ability actually is - they suffer from what is known as the Dunning-Kruger effect. Quote often these people have little or no formal training, but both types are downright dangerous for their customers and anyone working with them. I have to wonder if your man asked you to pay in cash. Unfortunately our system permits these people to exist because there is no equivalent of the American General Contractor qualification (as in some states) here. A competent, trained joiner would be aware of the need to get calcs made and to inform Building Control - the facts that your guy did such a pizz poor unsafe job, didn't get the calcs done and didn't involve BC speaks volumes about him. You've been had.

 

[Koolpc]

If it were me, i would def get a structural engineer in to do some calculations. Plus, you need to inform BC too.

Little cost in the grand scheme of things.

 

[Starfox1892]

Do you think that one day you might want to sell the house? Or remortage it? Or take Equity Release in your old age?

No we're going to keep it and rent it out when we move.

I just want to know if the method used is something that is acceptable, providing the calculations stack up and building control are happy.

 

[freddiemercurystwin]

Any method that can be proven will be acceptable. But it would be very unusual to use a purlin to suspend a floor from on the contrary normally the purlin is actually supported with a new structural beam with a new structual wall built above to support the purlin. Without Building Control approval the estate agent would not be able to market the porperty as having a habitable room in the loft, it will be forever an illegal loft conversion, god knows what else is being skimped on. Heyho.