Building new solid floor against wall with suspended wooden floor and
airbricks. The top of the airbricks are on a level with the top of the
floor slab (which is due to have 70mm screed on top for levelling
purposes). The floor slab will be 150mm thick, and is on top of 75mm
celotex and hardcore. An air path will be vented through the new
cavity wall using periscope ducting. So to join the air bricks via
ducting in the new solid floor.

I plan to cast a 2 to 3 inch high duct into the top of the floor slab
when it is layed to join the old and new airbricks, then cover this
with, say, a paving slabs before the screed goes down.
I'll put some metal into the concrete under the duct area since it
will only be around 3" thick there. Slab not thick enough to use 4"
soil pipe as is commonly done.

Do folks think this this will be OK ? Yes, I'll end up asking the BCO
of course.

Only other option is to use a perisope on both ends and duct it much
lower down (cut though insulation layer or hardcore layer), but this
is a more convoluted air path and does not seem ideal to me.

Thanks,
Simon.

On Mon, 23 Jun 2008 02:21:40 -0700 (PDT), a particular chimpanzee,
sm_jamieson randomly hit the keyboard and
produced:

Building new solid floor against wall with suspended wooden floor and
airbricks. The top of the airbricks are on a level with the top of the
floor slab (which is due to have 70mm screed on top for levelling
purposes). The floor slab will be 150mm thick, and is on top of 75mm
celotex and hardcore. An air path will be vented through the new
cavity wall using periscope ducting. So to join the air bricks via
ducting in the new solid floor.

I plan to cast a 2 to 3 inch high duct into the top of the floor slab
when it is layed to join the old and new airbricks, then cover this
with, say, a paving slabs before the screed goes down.
I'll put some metal into the concrete under the duct area since it
will only be around 3" thick there. Slab not thick enough to use 4"
soil pipe as is commonly done.

Do folks think this this will be OK ? Yes, I'll end up asking the BCO
of course.

The duct should be at least 100mm diameter, it should be covered by
the insulation, and by at least 100mm of concrete. It needs to go
through the hardcore. One hopes your original floor has a sub-floor
at least 5" (125mm) below the bottom of your (at least 100mm deep)
joists, so there should be plenty of space to take the pipe
horizontally through the existing wall.
--
Hugo Nebula
"If no-one on the internet wants a piece of this,
just how far from the pack have you strayed?"

On 23 Jun, 12:33, Hugo Nebula abuse@localhost wrote:
On Mon, 23 Jun 2008 02:21:40 -0700 (PDT), a particular chimpanzee,
sm_jamieson randomly hit the keyboard and
produced:



Building new solid floor against wall with suspended wooden floor and
airbricks. The top of the airbricks are on a level with the top of the
floor slab (which is due to have 70mm screed on top for levelling
purposes). The floor slab will be 150mm thick, and is on top of 75mm
celotex and hardcore. An air path will be vented through the new
cavity wall using periscope ducting. So to join the air bricks via
ducting in the new solid floor.

I plan to cast a 2 to 3 inch high duct into the top of the floor slab
when it is layed to join the old and new airbricks, then cover this
with, say, a paving slabs before the screed goes down.
I'll put some metal into the concrete under the duct area since it
will only be around 3" thick there. Slab not thick enough to use 4"
soil pipe as is commonly done.

Do folks think this this will be OK ? Yes, I'll end up asking the BCO
of course.

The duct should be at least 100mm diameter, it should be covered by
the insulation, and by at least 100mm of concrete. It needs to go
through the hardcore. One hopes your original floor has a sub-floor
at least 5" (125mm) below the bottom of your (at least 100mm deep)
joists, so there should be plenty of space to take the pipe
horizontally through the existing wall.
--

Is what you have said in the building regs, or just good practice ?
What part of the building regs is it ?

I would just have to make an opening through 9" wall and block up the
current air bricks. All possible. Sounds like you just treat it like a
drainage pipe (ish). No problem with the vertical space for this.

Thanks,
Simon.

On 23 Jun, 10:21, sm_jamieson wrote:
Building new solid floor against wall with suspended wooden floor and
airbricks. The top of the airbricks are on a level with the top of the
floor slab (which is due to have 70mm screed on top for levelling
purposes). The floor slab will be 150mm thick, and is on top of 75mm
celotex and hardcore. *An air path will be vented through the new
cavity wall using periscope ducting. So to join the air bricks via
ducting in the new solid floor.

I plan to cast a 2 to 3 inch high duct into the top of the floor slab
when it is layed to join the old and new airbricks, then cover this
with, say, a paving slabs before the screed goes down.
I'll put some metal into the concrete under the duct area since it
will only be around 3" thick there. Slab not thick enough to use 4"
soil pipe as is commonly done.

Do folks think this this will be OK *? Yes, I'll end up asking the BCO
of course.

Only other option is to use a perisope on both ends and duct it much
lower down (cut though insulation layer or hardcore layer), but this
is a more convoluted air path and does not seem ideal to me.

Thanks,
Simon.

I have been doing this sort of specification professionally for over
30 years and Hugh is dead right on all counts. I, personally, would go
to more than one 4" and preferably 6" pipes in the hard core.
(Allow for insect mesh at the outer end and put some form of vermin
mesh at the inner end of the pipe and leave a trap in the floorboards
to gain access to the pipes in the future if you need to)
Well done for realising the need for this
I make a living out of those who dont bother or whose architects
forget to put this detail in - it is usually wet rot in the plate
abutting the new floor about 20 years later!
chris

Chris

sm_jamieson wrote:
Building new solid floor against wall with suspended wooden floor and
airbricks. The top of the airbricks are on a level with the top of the
floor slab (which is due to have 70mm screed on top for levelling
purposes). The floor slab will be 150mm thick, and is on top of 75mm
celotex and hardcore. An air path will be vented through the new
cavity wall using periscope ducting. So to join the air bricks via
ducting in the new solid floor.

I plan to cast a 2 to 3 inch high duct into the top of the floor slab
when it is layed to join the old and new airbricks, then cover this
with, say, a paving slabs before the screed goes down.
I'll put some metal into the concrete under the duct area since it
will only be around 3" thick there. Slab not thick enough to use 4"
soil pipe as is commonly done.

Do folks think this this will be OK ? Yes, I'll end up asking the BCO
of course.


Many years ago I suffered from someone having done this job badly. The
suspended floor slowly deteriorated until it lost strength and started
to collapse.

Not worth skimping - at all - even if you can/could get it past the BCO.

--
Rod

Hypothyroidism is a seriously debilitating condition with an insidious
onset.
Although common it frequently goes undiagnosed.
www.thyromind.info www.thyroiduk.org www.altsupportthyroid.org

On 23 Jun, 13:20, wrote:
On 23 Jun, 10:21, sm_jamieson wrote:



Building new solid floor against wall with suspended wooden floor and
airbricks. The top of the airbricks are on a level with the top of the
floor slab (which is due to have 70mm screed on top for levelling
purposes). The floor slab will be 150mm thick, and is on top of 75mm
celotex and hardcore. An air path will be vented through the new
cavity wall using periscope ducting. So to join the air bricks via
ducting in the new solid floor.

I plan to cast a 2 to 3 inch high duct into the top of the floor slab
when it is layed to join the old and new airbricks, then cover this
with, say, a paving slabs before the screed goes down.
I'll put some metal into the concrete under the duct area since it
will only be around 3" thick there. Slab not thick enough to use 4"
soil pipe as is commonly done.

Do folks think this this will be OK ? Yes, I'll end up asking the BCO
of course.

Only other option is to use a perisope on both ends and duct it much
lower down (cut though insulation layer or hardcore layer), but this
is a more convoluted air path and does not seem ideal to me.

Thanks,
Simon.

I have been doing this sort of specification professionally for over
30 years and Hugh is dead right on all counts. I, personally, would go
to more than one 4" and preferably 6" pipes in the hard core.
(Allow for insect mesh at the outer end and put some form of vermin
mesh at the inner end of the pipe and leave a trap in the floorboards
to gain access to the pipes in the future if you need to)
Well done for realising the need for this
I make a living out of those who dont bother or whose architects
forget to put this detail in - it is usually wet rot in the plate
abutting the new floor about 20 years later!
chris

Chris

There is currently two air bricks venting the back room. If I put two
4" pipes to replace, I think this should be enough, since there will
be more area due to the pipes not having the restriction of the old
clay airbricks. I'll have to go around a 90 degree bend to get the
pipe to the correct position on the outside wall though.
If this is in the regs I guess it would be part F ?
Simon.

On 23 Jun, 12:33, Hugo Nebula abuse@localhost wrote:
On Mon, 23 Jun 2008 02:21:40 -0700 (PDT), a particular chimpanzee,
sm_jamieson randomly hit the keyboard and
produced:



Building new solid floor against wall with suspended wooden floor and
airbricks. The top of the airbricks are on a level with the top of the
floor slab (which is due to have 70mm screed on top for levelling
purposes). The floor slab will be 150mm thick, and is on top of 75mm
celotex and hardcore. An air path will be vented through the new
cavity wall using periscope ducting. So to join the air bricks via
ducting in the new solid floor.

I plan to cast a 2 to 3 inch high duct into the top of the floor slab
when it is layed to join the old and new airbricks, then cover this
with, say, a paving slabs before the screed goes down.
I'll put some metal into the concrete under the duct area since it
will only be around 3" thick there. Slab not thick enough to use 4"
soil pipe as is commonly done.

Do folks think this this will be OK ? Yes, I'll end up asking the BCO
of course.

The duct should be at least 100mm diameter, it should be covered by
the insulation, and by at least 100mm of concrete. It needs to go
through the hardcore. One hopes your original floor has a sub-floor
at least 5" (125mm) below the bottom of your (at least 100mm deep)
joists, so there should be plenty of space to take the pipe
horizontally through the existing wall.
--

It turns out the sub-floor / original foundation is not low enough to
have a pipe go out through the house wall and under the insulation in
the hardcore layer of the new slab, without descending down a little
way against the outside of the house wall. So it looks like I'll have
to use a periscope style duct on both ends of the 4" pipe, one end in
the new cavity, the other end against the house wall.
A bit like:
http://www.myhouseextension.com/slab3.htm
Since at the house wall the new floor slab and old suspended floor
will meet, I cannot have vertical insulation here anyway, like you do
between a floor slab and exterior wall, because I need the solid floor
to butt right up to the wall - there is no "edge" to hide the
insulation board with skirting etc.
I guess I could put celotex on the inside of the old house wall in the
sub-floor void to keep the slab partly insulated from the cold
underfloor void. There will still be cold bridging from the ground to
the new slab, but not much can be done about this.
Simon.

On Mon, 23 Jun 2008 05:12:41 -0700 (PDT), a particular chimpanzee,
sm_jamieson randomly hit the keyboard and
produced:

Is what you have said in the building regs, or just good practice ?
What part of the building regs is it ?

Approved Document C, Section 4.14(b).
--
Hugo Nebula
"If no-one on the internet wants a piece of this,
just how far from the pack have you strayed?"

On 23 Jun, 23:03, Hugo Nebula abuse@localhost wrote:
On Mon, 23 Jun 2008 05:12:41 -0700 (PDT), a particular chimpanzee,
sm_jamieson randomly hit the keyboard and
produced:

Is what you have said in the building regs, or just good practice ?
What part of the building regs is it ?

Approved Document C, Section 4.14(b).
--
Hugo Nebula
"If no-one on the internet wants a piece of this,
just how far from the pack have you strayed?"

Hum. Looking through part C, noticed section 5.
Says there should be 225mm clear vertical cavity above the cavity
infilling. Good job I noticed that. I've always been told fill sloping
down to ground level, when it should be sloping down from ground
level, such that the slope ends 3 courses down. I've done a small
stretch (with some spare concrete I had) one brick too high according
to that. I'm sure (hope) I won't be made to change it (drilling out
75mm would be a pain), but you find some things out rather late. Part
C was about the only doc. I hadn't scrutinized !
Cheers,
Simon.