Right we have covered the windows:-)

Question 2 concerns Posi-joists. Anyone have any reportable experience?

I have been told they creak.

For a similar load and span, I have been told they need a deeper section
than timber. But a plumber/wireman dream for easy access.

Heating designer is opposed because you can't cut a slot through the top
section to return the underfloor heating pipes.

The cottage will have 3 dormers leaving a small triangular space above
the eaves. I have been wondering about the practicality of keeping this
space warm (inside the insulation) and using it to return the heating
pipes. Sucking of teeth from engineer concerned about multiple air lock
sites.

Any thoughts?


--
Tim Lamb

On 20/05/16 22:21, Tim Lamb wrote:
Right we have covered the windows:-)

Question 2 concerns Posi-joists. Anyone have any reportable experience?

I have been told they creak.

For a similar load and span, I have been told they need a deeper section
than timber. But a plumber/wireman dream for easy access.

Heating designer is opposed because you can't cut a slot through the top
section to return the underfloor heating pipes.

The cottage will have 3 dormers leaving a small triangular space above
the eaves. I have been wondering about the practicality of keeping this
space warm (inside the insulation) and using it to return the heating
pipes. Sucking of teeth from engineer concerned about multiple air lock
sites.

Any thoughts?



I used mine (triangular voids) to contain cable basket trays.

The pipes will run in front and above this space at the expense of a
couple of inches of room space - and will have removable panelling for
easy access to pipes and wiring.

This also solves your joists problem - run along, then drop down
alongside the joist. No holes or notches.

With a sealed system, I don't see any issues (small bits of air tend to
get blown through and there should not be any large amounts of air after
pressurising. The plumber can add a bleeding valves at the high points
to aid filling the system.

Tim Lamb wrote:

Question 2 concerns Posi-joists.
Heating designer is opposed because you can't cut a slot through the top
section to return the underfloor heating pipes.

With all them 'oles in the metal web, why would you even want to cut slots?

On 21/05/2016 07:41, Andy Burns wrote:
Tim Lamb wrote:

Question 2 concerns Posi-joists.
Heating designer is opposed because you can't cut a slot through the top
section to return the underfloor heating pipes.

With all them 'oles in the metal web, why would you even want to cut slots?


So glad you asked that, Andy. Read the question last night and scratched
my head thinking I must be missing something. Still can't see what...

--
Rod

In message , Andy Burns
writes
Tim Lamb wrote:

Question 2 concerns Posi-joists.
Heating designer is opposed because you can't cut a slot through the top
section to return the underfloor heating pipes.

With all them 'oles in the metal web, why would you even want to cut slots?

Wet underfloor heating (Speedfit) uses aluminium spreader plates nailed
to the joist tops with the pipe run trapped in pre-formed channels. The
pipe has to go through or over the joist to reach the next joist pair.
Going through involves a lot of pipe threading.....



--
Tim Lamb

Tim Lamb wrote:

Andy Burns writes:

With all them 'oles in the metal web, why would you even want to cut slots?

Wet underfloor heating (Speedfit) uses aluminium spreader plates nailed
to the joist tops with the pipe run trapped in pre-formed channels. The
pipe has to go through or over the joist to reach the next joist pair.
Going through involves a lot of pipe threading.....

OK, I see. JG seem to recommend fixing the plates to the bottom of the
flooring when using engineered joists rather than to the top of the
joists ...

https://www.youtube.com/watch?v=gx2jEz3bfkk

In message , polygonum
writes
On 21/05/2016 07:41, Andy Burns wrote:
Tim Lamb wrote:

Question 2 concerns Posi-joists.
Heating designer is opposed because you can't cut a slot through the top
section to return the underfloor heating pipes.

With all them 'oles in the metal web, why would you even want to cut slots?


So glad you asked that, Andy. Read the question last night and
scratched my head thinking I must be missing something. Still can't see
what...

Sorry! Inadequate description. Heating engineer is used to dealing with
conventional timber joists and his fitters expect to be able to cut a
15mm depth slot in the joist top to cross into the next joist/pair run.
They nail on a *p* clip to retain the pipe.

Because this is a chalet bungalow where the internal walls upstairs are
some distance in from the outer walls (joist supports) I am resisting
having slots cut of any depth.

My thinking is to take the pipe under the wall and return through or
over the Posi- joist. Hence lots of places where a length of pipe is
able to trap air.


--
Tim Lamb

On 21/05/2016 08:49, Andy Burns wrote:
Tim Lamb wrote:

Andy Burns writes:

With all them 'oles in the metal web, why would you even want to cut
slots?

Wet underfloor heating (Speedfit) uses aluminium spreader plates nailed
to the joist tops with the pipe run trapped in pre-formed channels. The
pipe has to go through or over the joist to reach the next joist pair.
Going through involves a lot of pipe threading.....

OK, I see. JG seem to recommend fixing the plates to the bottom of the
flooring when using engineered joists rather than to the top of the
joists ...

https://www.youtube.com/watch?v=gx2jEz3bfkk

The OP wrote "... to return the underfloor heating pipes" - I did not
take that to mean the loops at the end of every joist.

Nevertheless, I cannot see any significant reason other than reducing
the threading of the pipe to cut slots rather than holes in the web.
And, if the layout is very simple, you could pull the pipe through all
the webs at one end, then pull more and more pipe through to form the
loops. Wouldn't seem to be that much of a problem.

--
Rod

In message , Andy Burns
writes
Tim Lamb wrote:

Andy Burns writes:

With all them 'oles in the metal web, why would you even want to cut slots?

Wet underfloor heating (Speedfit) uses aluminium spreader plates nailed
to the joist tops with the pipe run trapped in pre-formed channels. The
pipe has to go through or over the joist to reach the next joist pair.
Going through involves a lot of pipe threading.....

OK, I see. JG seem to recommend fixing the plates to the bottom of the
flooring when using engineered joists rather than to the top of the
joists ...

https://www.youtube.com/watch?v=gx2jEz3bfkk

Yes. Sometimes because the joist design requires the flooring to be
glued down. Fit from below still needs the pipe threading through the
joists and the spreader plates have to *trap* the pipe which requires
more convoluted folding.

I hope to find out more this weekend; visiting someone with an installed
system.

I will end up with a mix of existing timber joists at nominal 600mm
spacing and new at 400mm, timber or posi. The nominal 600 is a lie
because there are doubles under the dormer cheeks and partition wall as
well as extras for the stair well!

Insulation has to be fitted below the spreaders which is easier from
above.


--
Tim Lamb

In message , polygonum
writes
On 21/05/2016 08:49, Andy Burns wrote:
Tim Lamb wrote:

Andy Burns writes:

With all them 'oles in the metal web, why would you even want to cut
slots?

Wet underfloor heating (Speedfit) uses aluminium spreader plates nailed
to the joist tops with the pipe run trapped in pre-formed channels. The
pipe has to go through or over the joist to reach the next joist pair.
Going through involves a lot of pipe threading.....

OK, I see. JG seem to recommend fixing the plates to the bottom of the
flooring when using engineered joists rather than to the top of the
joists ...

https://www.youtube.com/watch?v=gx2jEz3bfkk

The OP wrote "... to return the underfloor heating pipes" - I did not
take that to mean the loops at the end of every joist.

Nevertheless, I cannot see any significant reason other than reducing
the threading of the pipe to cut slots rather than holes in the web.
And, if the layout is very simple, you could pull the pipe through all
the webs at one end, then pull more and more pipe through to form the
loops. Wouldn't seem to be that much of a problem.

I've not done it but say the new upstairs lounge, 7m long, is split into
2 heating circuits (say 6 loops) that is 90m of pipe at the start!

--
Tim Lamb

On 21/05/2016 08:57, Tim Lamb wrote:
In message , polygonum
writes
On 21/05/2016 07:41, Andy Burns wrote:
Tim Lamb wrote:

Question 2 concerns Posi-joists.
Heating designer is opposed because you can't cut a slot through the
top
section to return the underfloor heating pipes.

With all them 'oles in the metal web, why would you even want to cut
slots?


So glad you asked that, Andy. Read the question last night and
scratched my head thinking I must be missing something. Still can't
see what...

Sorry! Inadequate description. Heating engineer is used to dealing with
conventional timber joists and his fitters expect to be able to cut a
15mm depth slot in the joist top to cross into the next joist/pair run.
They nail on a *p* clip to retain the pipe.

Because this is a chalet bungalow where the internal walls upstairs are
some distance in from the outer walls (joist supports) I am resisting
having slots cut of any depth.

My thinking is to take the pipe under the wall and return through or
over the Posi- joist. Hence lots of places where a length of pipe is
able to trap air.

For a unvented (i.e. pressurised) primary heating circuit, air traps are
not really much of an issue. It may make it slight harder to drain down
completely, but filling is usually straight forward, even if you do have
to do a second round of bleeding and topping up once the system is running.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

In message , John
Rumm writes
On 21/05/2016 08:57, Tim Lamb wrote:
In message , polygonum
writes
On 21/05/2016 07:41, Andy Burns wrote:
Tim Lamb wrote:

Question 2 concerns Posi-joists.
Heating designer is opposed because you can't cut a slot through the
top
section to return the underfloor heating pipes.

With all them 'oles in the metal web, why would you even want to cut
slots?


So glad you asked that, Andy. Read the question last night and
scratched my head thinking I must be missing something. Still can't
see what...

Sorry! Inadequate description. Heating engineer is used to dealing with
conventional timber joists and his fitters expect to be able to cut a
15mm depth slot in the joist top to cross into the next joist/pair run.
They nail on a *p* clip to retain the pipe.

Because this is a chalet bungalow where the internal walls upstairs are
some distance in from the outer walls (joist supports) I am resisting
having slots cut of any depth.

My thinking is to take the pipe under the wall and return through or
over the Posi- joist. Hence lots of places where a length of pipe is
able to trap air.

For a unvented (i.e. pressurised) primary heating circuit, air traps
are not really much of an issue. It may make it slight harder to drain
down completely, but filling is usually straight forward, even if you
do have to do a second round of bleeding and topping up once the system
is running.

This what I was hoping to read:-)

Plenty of compressed air on farm so I could blow it out if needed.

I've not seen a Speedfit manifold but I guess you can manually close off
all the circuits and fill them one at a time on full pump pressure.



--
Tim Lamb

On 21/05/2016 13:02, Tim Lamb wrote:
In message , John
Rumm writes
On 21/05/2016 08:57, Tim Lamb wrote:
In message , polygonum
writes
On 21/05/2016 07:41, Andy Burns wrote:
Tim Lamb wrote:

Question 2 concerns Posi-joists.
Heating designer is opposed because you can't cut a slot through the
top
section to return the underfloor heating pipes.

With all them 'oles in the metal web, why would you even want to cut
slots?


So glad you asked that, Andy. Read the question last night and
scratched my head thinking I must be missing something. Still can't
see what...

Sorry! Inadequate description. Heating engineer is used to dealing with
conventional timber joists and his fitters expect to be able to cut a
15mm depth slot in the joist top to cross into the next joist/pair run.
They nail on a *p* clip to retain the pipe.

Because this is a chalet bungalow where the internal walls upstairs are
some distance in from the outer walls (joist supports) I am resisting
having slots cut of any depth.

My thinking is to take the pipe under the wall and return through or
over the Posi- joist. Hence lots of places where a length of pipe is
able to trap air.

For a unvented (i.e. pressurised) primary heating circuit, air traps
are not really much of an issue. It may make it slight harder to drain
down completely, but filling is usually straight forward, even if you
do have to do a second round of bleeding and topping up once the
system is running.

This what I was hoping to read:-)

Plenty of compressed air on farm so I could blow it out if needed.

I've not seen a Speedfit manifold but I guess you can manually close off
all the circuits and fill them one at a time on full pump pressure.

You are normally filling from mains pressure - so that soon displaces
the air IME.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

In message , John
Rumm writes
My thinking is to take the pipe under the wall and return through or
over the Posi- joist. Hence lots of places where a length of pipe is
able to trap air.

For a unvented (i.e. pressurised) primary heating circuit, air traps
are not really much of an issue. It may make it slight harder to drain
down completely, but filling is usually straight forward, even if you
do have to do a second round of bleeding and topping up once the
system is running.

This what I was hoping to read:-)

Plenty of compressed air on farm so I could blow it out if needed.

I've not seen a Speedfit manifold but I guess you can manually close off
all the circuits and fill them one at a time on full pump pressure.

You are normally filling from mains pressure - so that soon displaces
the air IME.

Just back from Suffolk! The underfloor heating pipes were all laid on
top of insulation and not routed through or over joists.

I asked how they attached the flooring and learned the chipboard was
glued at the half lap and simply laid on top of the slotted in heating
pipes!



--
Tim Lamb

On 22/05/16 23:01, Tim Lamb wrote:
In message , John
Rumm writes
My thinking is to take the pipe under the wall and return through or
over the Posi- joist. Hence lots of places where a length of pipe is
able to trap air.

For a unvented (i.e. pressurised) primary heating circuit, air traps
are not really much of an issue. It may make it slight harder to drain
down completely, but filling is usually straight forward, even if you
do have to do a second round of bleeding and topping up once the
system is running.

This what I was hoping to read:-)

Plenty of compressed air on farm so I could blow it out if needed.

I've not seen a Speedfit manifold but I guess you can manually close off
all the circuits and fill them one at a time on full pump pressure.

You are normally filling from mains pressure - so that soon displaces
the air IME.

Just back from Suffolk! The underfloor heating pipes were all laid on
top of insulation and not routed through or over joists.

I asked how they attached the flooring and learned the chipboard was
glued at the half lap and simply laid on top of the slotted in heating
pipes!

I've heard of chip over insulation (free floating) with solid concrete
underneath - but not over joists.

In message , Tim Watts
writes
On 22/05/16 23:01, Tim Lamb wrote:
In message , John
Rumm writes
You are normally filling from mains pressure - so that soon displaces
the air IME.

Just back from Suffolk! The underfloor heating pipes were all laid on
top of insulation and not routed through or over joists.

I asked how they attached the flooring and learned the chipboard was
glued at the half lap and simply laid on top of the slotted in heating
pipes!

I've heard of chip over insulation (free floating) with solid concrete
underneath - but not over joists.

Our ground floor will largely be chip over pipes slotted into insulation
on concrete oversite. The new bit is screed which I will tile.

Any thoughts about fitting insulation to PVC or shiplap clad dormers
prior to plasterboard.


--
Tim Lamb

On 23/05/16 09:09, Tim Lamb wrote:
In message , Tim Watts
writes
On 22/05/16 23:01, Tim Lamb wrote:
In message , John
Rumm writes
You are normally filling from mains pressure - so that soon displaces
the air IME.

Just back from Suffolk! The underfloor heating pipes were all laid on
top of insulation and not routed through or over joists.

I asked how they attached the flooring and learned the chipboard was
glued at the half lap and simply laid on top of the slotted in heating
pipes!

I've heard of chip over insulation (free floating) with solid concrete
underneath - but not over joists.

Our ground floor will largely be chip over pipes slotted into insulation
on concrete oversite. The new bit is screed which I will tile.

Any thoughts about fitting insulation to PVC or shiplap clad dormers
prior to plasterboard.



Yes - make sure the chip has direct support points through to the
concrete - do not just float it. What happens (every time IME) is that
a) Washing machines shake the whole room; b) the insulation compresses
by doorways due to constant pummelling; c) Use celotex, not jablite -
it's a bit more crush resistant.

They do make special non thermal bridging support blocks for this scenario.

Personally, I prefer the screed and/or the concrete to be on top of
insulation - then at least you get a solid stable floor.

In message , Tim Watts
writes
On 23/05/16 09:09, Tim Lamb wrote:
In message , Tim Watts
writes
On 22/05/16 23:01, Tim Lamb wrote:
In message , John
Rumm writes
You are normally filling from mains pressure - so that soon displaces
the air IME.

Just back from Suffolk! The underfloor heating pipes were all laid on
top of insulation and not routed through or over joists.

I asked how they attached the flooring and learned the chipboard was
glued at the half lap and simply laid on top of the slotted in heating
pipes!

I've heard of chip over insulation (free floating) with solid concrete
underneath - but not over joists.

Our ground floor will largely be chip over pipes slotted into insulation
on concrete oversite. The new bit is screed which I will tile.

Any thoughts about fitting insulation to PVC or shiplap clad dormers
prior to plasterboard.



Yes - make sure the chip has direct support points through to the
concrete - do not just float it. What happens (every time IME) is that
a) Washing machines shake the whole room; b) the insulation compresses
by doorways due to constant pummelling; c) Use celotex, not jablite -
it's a bit more crush resistant.

Fortunately we will only have a dishwasher in the kitchen. Tumble dryer
and WM are in the utility on screed. I take your point about the
doorways as this has been noticed with the existing chip over jablite.

They do make special non thermal bridging support blocks for this scenario.

OK

Personally, I prefer the screed and/or the concrete to be on top of
insulation - then at least you get a solid stable floor.

I think we are stuck with re-doing the existing for the old ground
floor. To change would mean burying the timber wall panels in screed.

--
Tim Lamb