Pitched roof problem after problem! errrgghhh

[ianwainwrightjones]

Can anyone one, clear up something for me? Had the joiner in to construct the pitch roof. Basically we had to drop the wall plate to one common course and a 30mm bed, due to the low pitch, otherwise the fascia would have been huge! The joined cut all the timber ready. I spoke to the local BCO who said this was not acceptable as the manufacturers for the eaves lintels state a minimum of 150mm on masonry. Ok we get a structural engineer in who does us some calcs and come up with a 100 x 50mm RHS (BOX SECTION). Sorted!! No, the joiner has birds mouthed the 200mm C16 timber over the the wall plate 1/3 in, all correct! But where the rafter sits on the pole plate that has been bolted to the wall, he has cut a birds mouth 1/2 way in so it sits flush with the bottom of the 4 x2. His argument is its stronger than fitting with a hoist hanger, butted up, as the timber is pushing against a solid wall? The BCO says it should be sitting with no more than 1/3 cut out! What is right? Can I stiffen up with joist hangers?

 

[ianwainwrightjones]

Few typos due to predictive text! Lol

 

[tony1851]

he has cut a birds mouth 1/2 way in so it sits flush with the bottom of the 4 x2. His argument is its stronger than fitting with a hoist hanger, butted up, as the timber is pushing against a solid wall? The BCO says it should be sitting with no more than 1/3 cut out! What is right? Can I stiffen up with joist hangers?

Presumably there's 100mm left?
That should be OK structurally, particularly as it's only roof loading rather than floor loading.
BCOs only go by rules of thumb and are not usually able to calculate.

 

[noseall]

A wee bit careless by the chippy in my opinion.

All he needed do was do a simple b/m notch onto the pole plate, i.e. enough for a decent 'seat' - say 50mm. The remaining meat of the plumb cut would then be butted against the wall.

The position of the pole plate should be decided by the rafters and not the other way around. We cut all the rafters, offer them into place then offer the pole up to the rafters.

 

[noseall]

Thinking about it a bit more.....

......provided the whole of the rafter end plumb cut is butting snug, whether that be the bit butting against the pole plate and/or the bit butting against the wall, then I don't actually understand where the BCO's problem is.

It is only like having a staggered plumb cut surely?

 

[tony1851]

Thinking about it a bit more.....

......provided the whole of the rafter end plumb cut is butting snug, whether that be the bit butting against the pole plate and/or the bit butting against the wall, then I don't actually understand where the BCO's problem is.

It is only like having a staggered plumb cut surely?

Exactly; where's the rafter going to go?
His BCO is a nit.

 

[ianwainwrightjones]

That was my thought and the thought of my joiner! It can't go anywhere as all 200mm is pushing against a solid wall albeit staggered, the same as the wall plate pushing down on the block work! What can I do? If I owe the BCO off he's just going be an arse for the rest!

 

[theoldun]

Sounds like the house that Jake built. Are you on full plans or building notice?
From scant information provided, we can only give a scant answer.
Assume it is a vaulted lean to with shallow pitch due to the fact that you have to get under first floor window sill level. We assume vaulted as ceiling joists are not mentioned and there would have been no need of a top birds beak on ledger plate if roof was coupled. Technically your BI is right in both instances. If you used a standard or eaves open back lintel you need 225mm of masonry below plate to achieve the composite design strength of the lintel to support the UDL Not knocking your SE in any way and not knowing what your roof covering is, have never never heard of a 50x100 box section supporting a roof load, and the subsequent problems you will have with soffit and cold bridge.
Once again your BI is technically right with regards your birds beak A birds mouth is your bottom cut over wall plate, but a birds beak is your top cut when you are hanging a rafter on to a ledger plate. By the way a pole plate in this country is a different animal with a different purpose., On a 200mm plus according to pitch, if we felt a birds beak was required we would have cut one third down for beak and a 25x50 London tenon on bottom of rafter.
Your comments about deep facia are rubbish, however on a shallow pitch you are left with a wide soffit, but there are numerous ways to over come this.
There are a number of ways to overcome your birds beak and ledger plate problem, but we need to know.
Your pitch
Size of ledger plate
Is roof vaulted
Span of roof
Roof covering
Regards oldun

 

[ianwainwrightjones]

Thanks for your response. I didn't get any plans drawn, just did it on a building notice(wish I had now) but that's what happens when you go off other people's comments and believe they not what they are doing!! The roof pitch is 13.5 degrees, span is 3.4, the roof covering will be tiled with Redland regent, the roof will be vaulted and the ledger plate is 100 x 50. I have decided to leave the eaves lintels in situe, resulting in the cavity being closed and additional strength. I have thought of may be filling the box section with expanding foam or insulation. Would this benefit at all? Could I fit 100 x 50 joist hangers to give extra support to the joists? Any help would be greatly appreciated.

 

[tony1851]

Could I fit 100 x 50 joist hangers to give extra support to the joists? Any help would be greatly appreciated.

Do you mean the tops of the rafters, where they meet the wall?

 

[ianwainwrightjones]

No at the bottom, so they fasten to the timber and support the bottom half of the joist!

 

[theoldun]

We often wonder just how much money people waste on working to a building notice, when neither they or their contractor know zit about construction or the BRs.
Easy options first for you to put in front of BI for his approval. Repeat his approval. The list of Simpsons fittings that we will give you, Google Simpsons web site and you will see what we mean
You can not fix rafters to joist hangers. End of.

1. Fix rafters as cut. Fix 50 x95 noggins in between rafters and on top of existing ledger plate and skew nail through noggins into birds beak
2, Fix rafters as cut. Fix 50 x95 noggin in between rafters and on top of existing ledger plate and use 2no A34/A35 framing anchors each side, top and bottom with parts A and B bent over top and bottom of ledger plate..
3. Fix rafters as cut and fit and screw a ABR/E/EB reinforced angle bracket to top of existing ledger plate and rafters birds beak
If he will not accept any of the above then
4. Your pitch is 13.5 degrees so your top plumb cut is 76.5 degrees. Fix another 50x100 ledger plate above existing. Cut the top birds beak of off rafters and use either RR ridge rafter connector with additional skew nails into plate or SPR 50 slope assembly rafter hanger.
You will have to order both the above. Could be 14 day delivery.
Regards oldun