Hello all,

I need to replace a 22mm pipe under the kitchen floor. The original one, it
appears, was put in when the house was built as there is no way I can get a
length under the joists.

The joists are 4" x 2" resting on brick supports. The routing would take the
pipe parallel to and 12" from the support.

Q. Can I cut a U shaped notch 22mm deep in the top of each 4" joist, 12" from
the support, without seriously weakening the joist?

Thanks

AndyM

Q. Can I cut a U shaped notch 22mm deep in the top of each 4" joist,
12" from
the support, without seriously weakening the joist?


I wouldn't, in that situation I would run the pipe under the joist, held
up with copper U clips... assuming there's room

LJ

"AndyM" wrote in message
...
Hello all,

I need to replace a 22mm pipe under the kitchen floor. The original one,
it
appears, was put in when the house was built as there is no way I can get
a
length under the joists.

The joists are 4" x 2" resting on brick supports. The routing would take
the
pipe parallel to and 12" from the support.

Q. Can I cut a U shaped notch 22mm deep in the top of each 4" joist, 12"
from
the support, without seriously weakening the joist?

Thanks

AndyM

================
Can you knock out an airbrick to feed the pipe in from outside the building?
If not, you can usually feed in short sections of pipe (through a gap in the
floorboards) and make soldered joints until the desired length is made up.

Cic.

AndyM wrote:
Hello all,

I need to replace a 22mm pipe under the kitchen floor. The original one, it
appears, was put in when the house was built as there is no way I can get a
length under the joists.

The joists are 4" x 2" resting on brick supports. The routing would take the
pipe parallel to and 12" from the support.

Q. Can I cut a U shaped notch 22mm deep in the top of each 4" joist, 12" from
the support, without seriously weakening the joist?

Thanks

AndyM
It depends on the joist length, all the info is here in simple form (or
look in bldg regs):
http://www.iee.org/Publish/WireRegs/...lding_Regs.pdf
--
Dave S
(The return email address is a dummy)

"AndyM" wrote in message
...
Hello all,

I need to replace a 22mm pipe under the kitchen floor. The original
one, it
appears, was put in when the house was built as there is no way I
can get a
length under the joists.

The joists are 4" x 2" resting on brick supports. The routing would
take the
pipe parallel to and 12" from the support.

Q. Can I cut a U shaped notch 22mm deep in the top of each 4"
joist, 12" from
the support, without seriously weakening the joist?

Thanks

AndyM

Use Hep2O and you can feed in as much as you like in a coil !

AWEM

"Andrew Mawson" wrote in message
...

"AndyM" wrote in message
...
Hello all,

I need to replace a 22mm pipe under the kitchen floor. The original
one, it
appears, was put in when the house was built as there is no way I
can get a
length under the joists.

The joists are 4" x 2" resting on brick supports. The routing would
take the
pipe parallel to and 12" from the support.

Q. Can I cut a U shaped notch 22mm deep in the top of each 4"
joist, 12" from
the support, without seriously weakening the joist?

Thanks

AndyM

Can't answer your queston without delving into the beam equations, but the
highest stressed parts of a joist are the top andthe bottom: something
called the 'neutral line' runs through the centre, which suffers neither
tension nor compression, only the shear (45 degree) forces that beams have.
Thus, it is true to say I think, that the least weakening of the beam will
occur if the hole goes through the middle of the beam.

Andy.

In article , "andrewpreece"
says...

"Andrew Mawson" wrote in message
...

"AndyM" wrote in message
...
Hello all,

I need to replace a 22mm pipe under the kitchen floor. The original
one, it
appears, was put in when the house was built as there is no way I
can get a
length under the joists.

The joists are 4" x 2" resting on brick supports. The routing would
take the
pipe parallel to and 12" from the support.

Q. Can I cut a U shaped notch 22mm deep in the top of each 4"
joist, 12" from
the support, without seriously weakening the joist?

Thanks

AndyM

Can't answer your queston without delving into the beam equations, but the
highest stressed parts of a joist are the top andthe bottom: something
called the 'neutral line' runs through the centre, which suffers neither
tension nor compression, only the shear (45 degree) forces that beams have.
Thus, it is true to say I think, that the least weakening of the beam will
occur if the hole goes through the middle of the beam.

Easier to run the pipe underneath in this case, I suspect.

Thanks very much.

(Looks like I'll go through the wall)

AndyM

So should I be worried that the guy that's installed central heating into a
renovated house cut a U section in the top of the beam ,of 1st floor.

John Borman wrote:

So should I be worried that the guy that's installed central heating into a
renovated house cut a U section in the top of the beam ,of 1st floor.


That depends.

If its then had e.g chipboard nailed on top, a lot of the strength and
stiffness is restored.

Note that the building regs tend to look at maximum defelection under
load, as ultimately failure load is way higher. You could have maybe 6"
of sag on a beam spanning 5 feet before it broke, but this is
unacceptable in a floor :-)

"The Natural Philosopher" wrote in message
...
John Borman wrote:

So should I be worried that the guy that's installed central heating into
a renovated house cut a U section in the top of the beam ,of 1st floor.
That depends.

If its then had e.g chipboard nailed on top, a lot of the strength and
stiffness is restored.

No chipboard just t&g floorboards....

Note that the building regs tend to look at maximum defelection under
load, as ultimately failure load is way higher. You could have maybe 6" of
sag on a beam spanning 5 feet before it broke, but this is unacceptable in
a floor :-)

"John Borman" wrote in message
...
"The Natural Philosopher" wrote in message
...
John Borman wrote:

So should I be worried that the guy that's installed central heating
into
a renovated house cut a U section in the top of the beam ,of 1st floor.
That depends.

If its then had e.g chipboard nailed on top, a lot of the strength and
stiffness is restored.

No chipboard just t&g floorboards....

The strength will be restored to a degree far better by using screws, not
nails.

AndyM wrote:
Hello all,

I need to replace a 22mm pipe under the kitchen floor. The original
one, it appears, was put in when the house was built as there is no
way I can get a length under the joists.

The joists are 4" x 2" resting on brick supports. The routing would
take the pipe parallel to and 12" from the support.

Q. Can I cut a U shaped notch 22mm deep in the top of each 4" joist,
12" from the support, without seriously weakening the joist?


Possibly, but you'd need to do the calculations to determine whether or not
it is acceptable without comprising the strength of the beam. Have you
considered cutting the old pipe out in sections and then feeder plastic pipe
in instead (e.g. Hep20 or Marley Equator)? Unless the joists are seriously
close together you should be able to fit plastic quite easily.

Cheers
Clive