We want to specify heavier than normal joists in the extension. What size
should we ask for?

Suzanne

Suz wrote:
We want to specify heavier than normal joists in the extension. What size
should we ask for?

Why?
What's the span between supports, and what's the load you want to put on
it?

Doubling the width, or doubling the frequency of joists doubles the
stiffness of the floor.
Doubling the height of the joists quadruples the stiffness.

The message
from "Suz" contains these words:

We want to specify heavier than normal joists in the extension. What size
should we ask for?

Someone else who wants a shagswing! (insert smiley of choice here).

Explain to whoever's designing it what the purpose of the extra strength
is and they'll make the calculations accordingly.

--
Skipweasel
Pay no attention to that man behind the curtain.

On 08 Dec 2006 18:03:27 GMT Ian Stirling wrote :
Doubling the height of the joists quadruples the stiffness.

Quadruples the strength, increases the stiffness by 8. Stiffness is
proportional to depth^3 , so just going from 150 to 175 high joists
increases the stiffness by nearly 60%

--
Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk

Tony Bryer wrote:
On 08 Dec 2006 18:03:27 GMT Ian Stirling wrote :
Doubling the height of the joists quadruples the stiffness.

Quadruples the strength, increases the stiffness by 8. Stiffness is
proportional to depth^3 , so just going from 150 to 175 high joists
increases the stiffness by nearly 60%

Err - yes.

Suz wrote:
We want to specify heavier than normal joists in the extension. What
size should we ask for?

Suzanne

Which joists?
ceiling or floor?
what for?

"Ian Stirling" wrote in message
...
Suz wrote:
We want to specify heavier than normal joists in the extension. What
size
should we ask for?

Why?
What's the span between supports, and what's the load you want to put
on
it?

If you tell him, don't believe his answer.

Doubling the width, or doubling the frequency of joists doubles the
stiffness of the floor.
Doubling the height of the joists quadruples the stiffness.

Maximum deflection is inversely proportional to the Moment of Inertia,
I. For a beam of rectangular cross section, I =b*d^3/12. So double
the width, double the stiffness, like the man said, but double the depth
of the beam, and it's 8 times as stiff.


--
Kevin Poole
**Use current month and year to reply (e.g. )***

"Ian Stirling" wrote in message
...
Suz wrote:
We want to specify heavier than normal joists in the extension. What
size
should we ask for?

Why?
What's the span between supports, and what's the load you want to put on
it?

Doubling the width, or doubling the frequency of joists doubles the
stiffness of the floor.
Doubling the height of the joists quadruples the stiffness.

Oh why is nothing ever simple?

The idea is to have real strudy floor to minimise any bend and noise
transference. The longest one will be in the roofspace and as the kids will
be there I want to reduce the elephantitis noise from above.

Suz wrote:
"Ian Stirling" wrote in message
...
Suz wrote:
We want to specify heavier than normal joists in the extension. What
size
should we ask for?

Why?
What's the span between supports, and what's the load you want to put on
it?

Doubling the width, or doubling the frequency of joists doubles the
stiffness of the floor.
Doubling the height of the joists quadruples the stiffness.

Oh why is nothing ever simple?

Because it's real life :/

The idea is to have real strudy floor to minimise any bend and noise
transference. The longest one will be in the roofspace and as the kids will
be there I want to reduce the elephantitis noise from above.

The other problem.
8" joists - compared to 6" will in fact moderately reduce noise.

What will reduce it a lot more is to completely float the floor.
You basically put in joists like:

______________
# # #
# # # # # #
# # # # # #
# # #
____________

Where there are two sets of joists, interspersed.
The bottom ones are maybe slightly smaller, as they only support the
plasterboard, the top ones support the floor above, and they only are
connected at the side walls, being completely free to move in relation
to each other.
Adding rockwool in the space in between helps too.

Suz wrote:
"Ian Stirling" wrote in message
...
Suz wrote:
We want to specify heavier than normal joists in the extension. What
size
should we ask for?

Why?
What's the span between supports, and what's the load you want to
put on it?

Doubling the width, or doubling the frequency of joists doubles the
stiffness of the floor.
Doubling the height of the joists quadruples the stiffness.

Oh why is nothing ever simple?

The idea is to have real strudy floor to minimise any bend and noise
transference. The longest one will be in the roofspace and as the
kids will be there I want to reduce the elephantitis noise from above.

You'd be wise to space the joists at 300mm instead of 400mm, rather than go
for more height on the joists...if you change the joist heights it might
(probably will) interfere with existing joist heights...you'll need sound
insulation between floors too, which is now required anyway.

"Suz" wrote

Oh why is nothing ever simple?

The idea is to have real strudy floor to minimise any bend and noise
transference. The longest one will be in the roofspace and as the kids
will
be there I want to reduce the elephantitis noise from above.

Hi,
If you're really after soundproofing rather than strength per se, a better
bet would be a normal (or slightly stiffer than usual) floor, with a
separate set of ceiling joists spaced between the floor joists and a few
inches lower (so that there's no mechanical coupling between the two) also
supported on the presumably-brick-and-block-walls, high-density rockwool
infill between 'em and two or more layers of plasterboard - this is how a
lot of home-studio builders do it to contain the noise - oops, music - as
much as possible, and what I'm aiming to do once SWMBC and I have the rest
of the place sorted...

Hope this helps,
Dave H.
(The engineer formerly known as Homeless)

Part E of the Building Regulations
(http://www.planningportal.gov.uk/eng...000000263.html)
has detailed guidance on soundproofing between floors.

"Phil L" wrote in message
. uk...
Suz wrote:
We want to specify heavier than normal joists in the extension. What
size should we ask for?

Suzanne

Which joists?
ceiling or floor?
what for?

The idea is to have real sturdy floor to minimise any bend and noise
transference. The longest one will be in the roofspace and as the kids will
be there I want to reduce the elephantitis noise from above.

I do know that insulation is needed too, but just want to use this
opportunity to make a really good addition to the house, not bare basics.

The message
from "Suz" contains these words:

The idea is to have real strudy floor to minimise any bend and noise
transference. The longest one will be in the roofspace and as the
kids will
be there I want to reduce the elephantitis noise from above.

Oh, none of the strenghening will do that. In fact a stiffer floor may
well transmit sound and vibration better than a more compliant floor.

What you want is a /soundproof/ floor - that's a different thing altogether.

--
Skipweasel
Pay no attention to that man behind the curtain.

Suz wrote:
"Phil L" wrote in message
. uk...
Suz wrote:

We want to specify heavier than normal joists in the extension. What
size should we ask for?

Which joists?
ceiling or floor?
what for?

The idea is to have real sturdy floor to minimise any bend and noise
transference. The longest one will be in the roofspace and as the kids will
be there I want to reduce the elephantitis noise from above.

I do know that insulation is needed too, but just want to use this
opportunity to make a really good addition to the house, not bare basics.

New build joist sizes are already on the excessive side. Suggest
instead a floating ceiling below and not attached to the floor. This
means a separate set of 2x3 joists just to support the ceiling. Much
more effective.

The other thing is the floor above. A floating wood on underlay on wood
floor will help further.

Finally sealing up of all gaps, however small, makes a real difference.
But not nostrils.


NT

Suz wrote:

Oh why is nothing ever simple?

The idea is to have real strudy floor to minimise any bend and noise
transference. The longest one will be in the roofspace and as the kids will
be there I want to reduce the elephantitis noise from above.

As the others said, the best way to do this is to de-couple your ceiling
from their floor. Insulation between helps, as does choosing a really
good carpet underlay for the new floor.

Have a look at what I did for my loft:

http://www.internode.co.uk/loft/floor.htm

The last couple of piccies show it best. I still had a small amount of
coupling between floor and ceiling since I needed to provide the lateral
bracing that used to be archived with tie beams. But even with this
there is noticeably less noise transmitted between 2nd and 1st floors
than there is between 1st and ground floors for example.

(and in spite of first-born in the room above being small and looking
rather dainty, seems to move with the acoustic aplomb of a small heard
of buffalo... nice thing is you can hardly hear it through the ceiling)

Another way to increase floor stiffness is with herringbone straps
across the joists either in the mid span or at 1/3 and 2/3 span. These
can either be cut from timber and done in the traditional way, or using
modern galvanised ones. Either way they just nail in place.

--
Cheers,

John.

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

John Rumm wrote:

I still had a small amount of
coupling between floor and ceiling since I needed to provide the lateral
bracing that used to be archived with tie beams.

Maybe you have a spalling chucker probe lamb.

(and in spite of first-born in the room above being small and looking
rather dainty, seems to move with the acoustic aplomb of a small heard
of buffalo... nice thing is you can hardly hear it through the ceiling)

I wonder how long it'll take the BR people to realise not being able to
hear that thud is a safety risk, and decree all this soundproofing be
removed.


NT

On 9 Dec 2006 02:42:48 -0800, a particular chimpanzee named
randomly hit the keyboard and produced:

I wonder how long it'll take the BR people to realise not being able to
hear that thud is a safety risk, and decree all this soundproofing be
removed.

What! Remove a Requirement! Are you MAD!!!

No, the proper way to go is to require that all surfaces in dwellings
up to 1100mm high are not climbable and have a hardness rating of
0.45[units] or less, as measured using an extremely complex formula
reproduced in secondary documentation to accompany Approved Document
R, published six months after the introduction of the Regulation.

If you are buying new furniture, you will have to submit a Building
Notice to the local authority, who will inspect it and require you to
have independent verification of its hardness rating (the Ikea
catalogue will not be sufficient), or else you can employ a competent
furniture installer who is a member of SOFASA (Sofa self-assessment
scheme) who will issue a certificate of compliance to the local
authority.
--
Hugo Nebula
"If no-one on the internet wants a piece of this,
just how far from the pack have you strayed?"

Hugo Nebula wrote:

What! Remove a Requirement! Are you MAD!!!

No, the proper way to go is to require that all surfaces in dwellings
up to 1100mm high are not climbable and have a hardness rating of
0.45[units] or less, as measured using an extremely complex formula
reproduced in secondary documentation to accompany Approved Document
R, published six months after the introduction of the Regulation.

If you are buying new furniture, you will have to submit a Building
Notice to the local authority, who will inspect it and require you to
have independent verification of its hardness rating (the Ikea
catalogue will not be sufficient), or else you can employ a competent
furniture installer who is a member of SOFASA (Sofa self-assessment
scheme) who will issue a certificate of compliance to the local
authority.

You know you should not make suggestions like this in a public forum,
you never know who might be reading! Especially when it makes about as
much sense as part P.

--
Cheers,

John.

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

wrote:

John Rumm wrote:


I still had a small amount of
coupling between floor and ceiling since I needed to provide the lateral
bracing that used to be archived with tie beams.


Maybe you have a spalling chucker probe lamb.

I had to read that three times before I spotted it.... ;-)

The Mozilla spelling checker is not that good at my brand of goof it
seems - sometimes we get to an impasse - I know its wrong, it says its
wrong, but it can't suggest an alternative no matter how many attempts
of subtly different but still wrong variations I try!

(although in the case above I obviously did not read what it suggested
to carefully!)


--
Cheers,

John.

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

John Rumm wrote:
wrote:

John Rumm wrote:


I still had a small amount of
coupling between floor and ceiling since I needed to provide the lateral
bracing that used to be archived with tie beams.


Maybe you have a spalling chucker probe lamb.

I had to read that three times before I spotted it.... ;-)

The Mozilla spelling checker is not that good at my brand of goof it
seems - sometimes we get to an impasse - I know its wrong, it says its
wrong, but it can't suggest an alternative no matter how many attempts
of subtly different but still wrong variations I try!

I find in the rare situations when I hit this sort of problem, a
thesaurus can help.
Although I've taken to entering the word in google - quite often the
'did you mean' entry will be the right one.

John Rumm wrote:
Hugo Nebula wrote:

What! Remove a Requirement! Are you MAD!!!

No, the proper way to go is to require that all surfaces in dwellings
up to 1100mm high are not climbable and have a hardness rating of
0.45[units] or less, as measured using an extremely complex formula
reproduced in secondary documentation to accompany Approved Document
R, published six months after the introduction of the Regulation.

If you are buying new furniture, you will have to submit a Building
Notice to the local authority, who will inspect it and require you to
have independent verification of its hardness rating (the Ikea
catalogue will not be sufficient), or else you can employ a competent
furniture installer who is a member of SOFASA (Sofa self-assessment
scheme) who will issue a certificate of compliance to the local
authority.

You know you should not make suggestions like this in a public forum,
you never know who might be reading! Especially when it makes about as
much sense as part P.

Its scarily realistic.

NT

Ian Stirling wrote:

The Mozilla spelling checker is not that good at my brand of goof it
seems - sometimes we get to an impasse - I know its wrong, it says its
wrong, but it can't suggest an alternative no matter how many attempts
of subtly different but still wrong variations I try!


I find in the rare situations when I hit this sort of problem, a
thesaurus can help.
Although I've taken to entering the word in google - quite often the
'did you mean' entry will be the right one.

Yup, google is probably quick way... I normally fire up Word or
something and get that to suggest something. The best electronic
dictionary I have used, was Proximity Technology's Linguibase - they
used to licenses it to a number of word pro vendors. That seemed to have
an almost supernatural ability to predict what I meant even if what I
typed bore no resemblance to it.

--
Cheers,

John.

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

On Sat, 09 Dec 2006 11:20:11 +0000, Hugo Nebula wrote:

On 9 Dec 2006 02:42:48 -0800, a particular chimpanzee named
randomly hit the keyboard and produced:

I wonder how long it'll take the BR people to realise not being able to
hear that thud is a safety risk, and decree all this soundproofing be
removed.

What! Remove a Requirement! Are you MAD!!!

No, the proper way to go is to require that all surfaces in dwellings
up to 1100mm high are not climbable and have a hardness rating of
0.45[units] or less, as measured using an extremely complex formula
reproduced in secondary documentation to accompany Approved Document
R, published six months after the introduction of the Regulation.

If you are buying new furniture, you will have to submit a Building
Notice to the local authority, who will inspect it and require you to
have independent verification of its hardness rating (the Ikea
catalogue will not be sufficient), or else you can employ a competent
furniture installer who is a member of SOFASA (Sofa self-assessment
scheme) who will issue a certificate of compliance to the local
authority.

I can see it now

The marketing by SOFASA "Sofar! Sofast! So good!", don't trust anyone else
with your living room.

The marketing in the shops (SOFASA registered)
"Part R compliant sofa's (sic), huge range, huge discounts."



--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html
Gas Fitting Standards Docs he http://www.makewrite.demon.co.uk/GasFittingStandards

Hugo Nebula abuse@localhost wrote:
On 9 Dec 2006 02:42:48 -0800, a particular chimpanzee named
randomly hit the keyboard and produced:

I wonder how long it'll take the BR people to realise not being able to
hear that thud is a safety risk, and decree all this soundproofing be
removed.

What! Remove a Requirement! Are you MAD!!!

No, the proper way to go is to require that all surfaces in dwellings
up to 1100mm high are not climbable and have a hardness rating of
0.45[units] or less, as measured using an extremely complex formula
reproduced in secondary documentation to accompany Approved Document

The easy other way to vastly improve safety, as well as open up a
enormous housing resource for key workers would be to simply mandate a
ceiling height of 1100mm.