Single storey extension.
I have to attach roof purlins to inner leaf of aircrete wall for a
single storey extension. The choice is - build the joist into the
aircrete wall, or use joist hangers suitable suitable for no blocks
above, e.g. strongtie safety fast joists hanger (this seems to be a
fairly new product). To be honest, building in seems a more sturdy
solution.
Which method should I use ?
Simon.

On 25 June, 14:43, wrote:
On 25 Jun, *
* * *"Bob Mannix" wrote:





"sm_jamieson" wrote in message
....
Single storey extension.
I have to attach roof purlins to inner leaf of aircrete wall for a
single storey extension. The choice is - build the joist into the
aircrete wall, or use joist hangers suitable suitable for no blocks
above, e.g. strongtie safety fast joists hanger (this seems to be a
fairly new product). To be honest, building in seems a more sturdy
solution.
Which method should I use ?
Simon.

I am neither a builder or a structural engineer but, if it was me, I would
assume that timber roofs are flexible structures that will move (if only
slightly) with temperature, wind etc. I would always build a purlin into a
wall so it was resting over the full thickness of the wall on the wall
beneath without the use of fixings in aircrete! ymmv

Is building in still allowed under building regs? It isn't allowed for floor
joists.

If not, that could explain the appearance of the joist hangers for the
top of a wall with no building over. But there only appears to be one
version out there.
Floor joists, there is always building over.
I'll have to check the regs.
Simon.

wrote:
Is building in still allowed under building regs? It isn't allowed for floor
joists.

What is the rationale behind that? Is it for insulation reasons?

On 25 June, 15:04, Jim wrote:
wrote:
Is building in still allowed under building regs? It isn't allowed for floor
joists.

What is the rationale behind that? Is it for insulation reasons?

Rot at the ends.

On 25 June, 12:24, sm_jamieson wrote:
Single storey extension.
I have to attach roof purlins to inner leaf of aircrete wall for a
single storey extension. The choice is - build the joist into the
aircrete wall, or use joist hangers suitable suitable for no blocks
above, e.g. strongtie safety fast joists hanger (this seems to be a
fairly new product). To be honest, building in seems a more sturdy
solution.
Which method should I use ?
Simon.

When you say purlins/joists, do you mean rafters?

If so the usual thing to do is to put a wall-plate on top of the wall,
and attach the rafters to that. The wall plate is mostly held by
gravity but also tied down to the wall with galv strapping to stop and
wind-lift.

Mentioning purlins makes me think that isn't your issue though.

wrote in message ...

Is building in still allowed under building regs? It isn't allowed for
floor
joists.

Since when were floor joists only allowed on hangers? Which is better as
gaps around the joists allow cold air into the floor spaces from the
cavities. Cavity wall insulation stops it and insulates.

"Bolted" wrote in message
...
On 25 June, 12:24, sm_jamieson wrote:
Single storey extension.
I have to attach roof purlins to inner leaf of aircrete wall for a
single storey extension. The choice is - build the joist into the
aircrete wall, or use joist hangers suitable suitable for no blocks
above, e.g. strongtie safety fast joists hanger (this seems to be a
fairly new product). To be honest, building in seems a more sturdy
solution.
Which method should I use ?
Simon.

When you say purlins/joists, do you mean rafters?

If so the usual thing to do is to put a wall-plate on top of the wall,
and attach the rafters to that. The wall plate is mostly held by
gravity but also tied down to the wall with galv strapping to stop and
wind-lift.

Correct. Make sure the wall-plate, which can be just a plank, is well
secured down. High winds can rip a roof off and wind speeds are getting
higher.

On 25 June, 16:00, Bolted wrote:
On 25 June, 12:24, sm_jamieson wrote:

Single storey extension.
I have to attach roof purlins to inner leaf of aircrete wall for a
single storey extension. The choice is - build the joist into the
aircrete wall, or use joist hangers suitable suitable for no blocks
above, e.g. strongtie safety fast joists hanger (this seems to be a
fairly new product). To be honest, building in seems a more sturdy
solution.
Which method should I use ?
Simon.

When you say purlins/joists, do you mean rafters?

If so the usual thing to do is to put a wall-plate on top of the wall,
and attach the rafters to that. *The wall plate is mostly held by
gravity but also tied down to the wall with galv strapping to stop and
wind-lift.

Mentioning purlins makes me think that isn't your issue though.

I mean purlins, yes, fixed at various heights up the roof slope.
See previous posts for my complicated roof details !
Think a metal factory roof but in timber, with several purlins
(parallel to the roof slope) carrying the main weight of the roof,
thinner rafters over the purlins.
Cheers,
Simon.

On Thu, 25 Jun 2009 16:38:42 +0100, Doctor Drivel wrote:

High winds can rip a roof off and wind speeds are getting
higher.

All the hot air from the green brigade?

I suppose we can just throw up millions of wind turbines to act as
friction brakes.

:-)

On 25 June, 16:40, Simon wrote:
On 25 June, 16:00, Bolted wrote:





On 25 June, 12:24, sm_jamieson wrote:

Single storey extension.
I have to attach roof purlins to inner leaf of aircrete wall for a
single storey extension. The choice is - build the joist into the
aircrete wall, or use joist hangers suitable suitable for no blocks
above, e.g. strongtie safety fast joists hanger (this seems to be a
fairly new product). To be honest, building in seems a more sturdy
solution.
Which method should I use ?
Simon.

When you say purlins/joists, do you mean rafters?

If so the usual thing to do is to put a wall-plate on top of the wall,
and attach the rafters to that. *The wall plate is mostly held by
gravity but also tied down to the wall with galv strapping to stop and
wind-lift.

Mentioning purlins makes me think that isn't your issue though.

I mean purlins, yes, fixed at various heights up the roof slope.
See previous posts for my complicated roof details !
Think a metal factory roof but in timber, with several purlins
(parallel to the roof slope) carrying the main weight of the roof,
thinner rafters over the purlins.
Cheers,
Simon.- Hide quoted text -

- Show quoted text -

Ah, OK, got you - purlin to gable wall.

Beyond my knowledge, really - I think they are often just built in or
supported on struts. Mine are corbelled but that was 120yrs ago, and
not aircrete!

sm_jamieson wrote:
Single storey extension.
I have to attach roof purlins to inner leaf of aircrete wall for a
single storey extension. The choice is - build the joist into the
aircrete wall, or use joist hangers suitable suitable for no blocks
above, e.g. strongtie safety fast joists hanger (this seems to be a
fairly new product). To be honest, building in seems a more sturdy
solution.
Which method should I use ?
Simon.

Build them in.

And use pre-stressed padtones to sit them on (cheap as chips)

--
Phil L
RSRL Tipster Of The Year 2008

sm_jamieson wrote:
Single storey extension.
I have to attach roof purlins to inner leaf of aircrete wall for a
single storey extension. The choice is - build the joist into the
aircrete wall, or use joist hangers suitable suitable for no blocks
above, e.g. strongtie safety fast joists hanger (this seems to be a
fairly new product). To be honest, building in seems a more sturdy
solution.
Which method should I use ?
Simon.

What do your plans say - and are you talking about a floor joist, ceiling
joist, roof rafter or roof purlin?

No matter, if possible, simply build them in and make sure that you put a
bit of DPC or slate under them and compo all round 'em as well - BTW, make
sure that the end don't protrude into the cavity.

On 25 June, 19:49, "Phil L" wrote:
sm_jamieson wrote:
Single storey extension.
I have to attach roof purlins to inner leaf of aircrete wall for a
single storey extension. The choice is - build the joist into the
aircrete wall, or use joist hangers suitable suitable for no blocks
above, e.g. strongtie safety fast joists hanger (this seems to be a
fairly new product). To be honest, building in seems a more sturdy
solution.
Which method should I use ?
Simon.

Build them in.

And use pre-stressed padtones to sit them on (cheap as chips)

Apparently, a single engineering brick is often used for this (75mm
wide timber onto aircrete).
Simon.

"Jules" wrote in message
news
On Thu, 25 Jun 2009 16:38:42 +0100, Doctor Drivel wrote:

High winds can rip a roof off and wind speeds are getting
higher.

All the hot air from the green brigade?

No, wind speeds are getting higher. Tornados are now more common.

I suppose we can just throw up millions of wind turbines to act as
friction brakes.

Positive thinking.

On Thu, 25 Jun 2009 14:43:56 +0100, a certain chimpanzee,
randomly hit a keyboard and produced:

Is building in still allowed under building regs? It isn't allowed for floor
joists.

It's still allowed, but not recommended. If they're built-in, you need
to make sure they're well mortared in and sealed with a flexible
sealant.
--
Hugo Nebula
"If no one on the Internet wants a piece of this,
just how far from the pack have you strayed?"

On Thu, 25 Jun 2009 15:04:07 +0100, a certain chimpanzee, Jim
randomly hit a keyboard and produced:

wrote:
Is building in still allowed under building regs? It isn't allowed for floor
joists.

What is the rationale behind that? Is it for insulation reasons?

Thermal and sound insulation. Thermal, as the gaps around their edges
can allow air through into the cavity, so an issue on external walls.
Sound for the same reason but, obviously, only an issue on party
walls.
--
Hugo Nebula
"If no one on the Internet wants a piece of this,
just how far from the pack have you strayed?"

On 28 June, 10:38, Hugo Nebula abuse@localhost wrote:
On Thu, 25 Jun 2009 14:43:56 +0100, a certain chimpanzee,
randomly hit a keyboard and produced:

Is building in still allowed under building regs? It isn't allowed for floor
joists.

It's still allowed, but not recommended. If they're built-in, you need
to make sure they're well mortared in and sealed with a flexible
sealant.
--
Seems more reasonable to build in for purlin fixings than with floor
joists. I'm not sure about
those joist hangers on a top row of aircrete.
I notice you can also get strongtie safety fast rubber boots for
buildng in to fix the air leakage problem.
Simon.