In this episode of my granite fitting saga, it appears that there won't be
enough room for the 40mm wooden beam across the twin appliance gap to
support the granite. What width steel box section would have the same
bending resistance as the 40mm wood specified?

Also, can granite rest directly on the metal, or should there be a soft
material on top, such as hardboard?

Christian.

On Mon, 23 Feb 2004 13:43:25 -0000, "Christian McArdle"
wrote:

In this episode of my granite fitting saga, it appears that there won't be
enough room for the 40mm wooden beam across the twin appliance gap to
support the granite. What width steel box section would have the same
bending resistance as the 40mm wood specified?

Also, can granite rest directly on the metal, or should there be a soft
material on top, such as hardboard?

I would suggest using something softish, or at least some silicone
sealant to allow for small movement.



..andy

To email, substitute .nospam with .gl

Christian McArdle wrote:

In this episode of my granite fitting saga, it appears that there won't be
enough room for the 40mm wooden beam across the twin appliance gap to
support the granite. What width steel box section would have the same
bending resistance as the 40mm wood specified?

Use 3mm walled box section, as thick as you can fit in there. 40mmx20mm
would be plenty, but the thicker the better.


Also, can granite rest directly on the metal, or should there be a soft
material on top, such as hardboard?

I'd want a cushion of silicone between the steel and the granite.


--
Grunff

Use 3mm walled box section, as thick as you can fit in there. 40mmx20mm
would be plenty, but the thicker the better.

So 20mm high will be enough to stop the Granite cracking when the
uninitiated decide to sit on the worktop? How many should I put across? I
was thinking of one near the front and one in the middle. The rear will be
held by some 2x3 softwood bolted to the wall.

I should just squeeze 20mm in. I've got around 45mm absolute tops to play
with. 40mm would be safer, making it easier to insert/retract appliances and
less likely to end in tears. I can't lift the worktop another mm without
serious issues elsewhere.

I've got to get the beam, slate, tile adhesive and sealant in there then.
I've already got the 12mm ply down, so don't need to account for that.

That gives:

Adhesive 3mm
Slate 12mm
Beam 20mm
Sealant 5mm

That gives me exactly 40mm, so it should be OK, provided I spread adhesive
carefully.

I take it I can just run a thick bed of sealant and let it dry? I don't
think I want to glue the granite down? Is there a more suitable material for
this anyway, such as laying thin MDF/hardboard over the entire space?

Christian.

On Mon, 23 Feb 2004 13:43:25 -0000, "Christian McArdle"
wrote:

In this episode of my granite fitting saga, it appears that there won't be
enough room for the 40mm wooden beam across the twin appliance gap to
support the granite. What width steel box section would have the same
bending resistance as the 40mm wood specified?

Also, can granite rest directly on the metal, or should there be a soft
material on top, such as hardboard?

Christian.

[T] I think the issue here is that granite isn't very flexible and
most other things are?

If you placed a length of your selected section on two blocks (same
spacing as your cabinets) and pressed in the middle, I think you'd
find pretty well anything will 'give'?

Is there any way you could fit a wall bolted, 'triangular' shaped,
steel brace in the middle or do you need an uncluttered space?

All the best ..

T i m

p.s. My feelings about how much apparently rigid things bend has been
enhanced since I have been using my 10 tonne hydraulic press. I
gas-cut a couple of 20mm steel plates, 50cm x 25 cm to act as a bed
for items on the press. The plates were a bit warped so I thought I'd
have a go at bending them straight with the press. Raised the ends and
pressed in the middle and they bend back easily .. (well, a couple of
tonnes worth of 'easily') ;-)

Is there any way you could fit a wall bolted, 'triangular' shaped,
steel brace in the middle or do you need an uncluttered space?

I'd need to drill a very big hole through the washing machine to accommodate
the brace. It might prevent the drum rotating, too.

Seriously, though. I've been told that a 40mm wooden beam across the front
is sufficient. I just want to know if I can reduce this using a metal beam
(or several) as I don't have 40mm to play with. There is absolutely no way
that any part of the structure can extend more than 25mm below the bottom of
the worktop over the 121cm span.

Christian.

On Tue, 24 Feb 2004 09:34:14 -0000, "Christian McArdle"
wrote:

Is there any way you could fit a wall bolted, 'triangular' shaped,
steel brace in the middle or do you need an uncluttered space?

I'd need to drill a very big hole through the washing machine to accommodate
the brace. It might prevent the drum rotating, too.

[T] Ok, so it's 'doable' then ;-)

Seriously, though. I've been told that a 40mm wooden beam across the front
is sufficient.

[T] Sounds like the suppliers I know .. ;-) "Yes just hit it hard with
a hammer .. it will be fine .... oh you did and it broke ... click ..
brrrrrrrrrrrrrr "

I just want to know if I can reduce this using a metal beam
(or several) as I don't have 40mm to play with. There is absolutely no way
that any part of the structure can extend more than 25mm below the bottom of
the worktop over the 121cm span.

[T] I see ... theres no doubt that a piece of hard wood will help but
would it be enough to prevent an expensive lump of slate / marble
snapping in half if someone sits / climbs on there by mistake. You
have see the large glass table tops being smashed on 'Youv'e been
framed' when folk treat them the wrong way?

(Like when my 'terrified of heights' friend went up the CN tower and
the kids were jumping up and down on the glass floor some hundreds of
feet above the ground ... I would be looking for stress fractures,
loosse bolts, rust or maybe NOT walk over the glass sections at all
(just in case).

I digress. Any decent section of steel would probably be stiffer than
the same size wood. The deeper the 'wall' the stiffer the box, the
problem is you would have to have it round the 'short' way.

I have some lengths of 50mm x 25mm x 1.5mm thick seam welded steel box
left over from when I built the garage doors. It's pretty stiff
(unlike angle) and probably stiffer than the support the cupboards can
provide?

Sit the top on that with a couple of strips of 1mm thick double sided
foam to provide the cushion and that's about the best you can do in
the space?

I assume you wouldn't be able to take the box section along the entire
length of the worktop (this would provide more support?)

All the best ..

T i m

Christian McArdle wrote:

Is there any way you could fit a wall bolted, 'triangular' shaped,
steel brace in the middle or do you need an uncluttered space?

I'd need to drill a very big hole through the washing machine to accommodate
the brace. It might prevent the drum rotating, too.


Hmmm, I take it we are talking about this layout, from your thread
"Granite worktop span"?

++----+----++----+---+----+---+---+
|| WM | TD || DW | +----+ | |
|| | || | 1 |SINK| 2 | 3 |
++----+----++----+---+ +---+---+

Support profile:
^^ 1.2m ^^ ^ ^ ^ ^ ^

You need a support 'twixt the WM and TD, yes? How about this (which is
what I thought Tim meant but, judging by his reaction to your reply, it
wasn't) fabricate a "shelf bracket" from angle iron and flat strip, it
only needs to be 3mm thick steel, screw it _solidly_ to the wall at the
back of the worktop. It will be more than strong enough. All you need is
3mm of space between the WM and TD, surely you must have that?

I couldn't draw it in ASCII art, so here's a quick CAD drawing of what I
mean. http://users.uk.freebsd.org/~mark/support.png

Regards,

Parish

Seriously, though. I've been told that a 40mm wooden beam across the front
is sufficient. I just want to know if I can reduce this using a metal beam
(or several) as I don't have 40mm to play with. There is absolutely no way
that any part of the structure can extend more than 25mm below the bottom of
the worktop over the 121cm span.

Christian.

I have some lengths of 50mm x 25mm x 1.5mm thick seam welded steel box
left over from when I built the garage doors. It's pretty stiff
(unlike angle) and probably stiffer than the support the cupboards can
provide?

25mm is, perhaps, a little too much, but pretty close. Although the
instructions call for 40mm wooden beam across the front, I am hoping that
doing several structs of metal 20mm will provide enough support.

I assume you wouldn't be able to take the box section along the entire
length of the worktop (this would provide more support?)

No. The next item is the dishwasher, which must be flush against the
worktop, unlike the washing machine and tumble dryer, which have the
facility to bolt the doors artificially high to cover the gap. Between the
dishwasher and tumble dryer is a stud framework with a pretty column pillar
on the front. The studwork is made of 47mm x 75mm softwood, so should
provide enough support for the metal lintels. I was planning to channel out
about 30mm for the lintel footings with a router.

Christian.

I have some lengths of 50mm x 25mm x 1.5mm thick seam welded steel box
left over from when I built the garage doors.

Well, I've got a quote of 40 quid for enough 3/4" x 3/4" 16 gauge to span 3
times. That, I believe means 19mm x 19mm @ 1.5mm thick. Hopefully, this will
be stiff enough to stop the Granite cracking. It also gives me space for a
5mm MDF sheet over the top, which should make the worktop fitting a bit
easier. I will measure again carefully, in case I can fit the 1" stuff in.

Christian.

On Tue, 24 Feb 2004 13:19:08 +0000, Parish wrote:

Christian McArdle wrote:

Is there any way you could fit a wall bolted, 'triangular' shaped,
steel brace in the middle or do you need an uncluttered space?

I'd need to drill a very big hole through the washing machine to accommodate
the brace. It might prevent the drum rotating, too.


Hmmm, I take it we are talking about this layout, from your thread
"Granite worktop span"?

++----+----++----+---+----+---+---+
|| WM | TD || DW | +----+ | |
|| | || | 1 |SINK| 2 | 3 |
++----+----++----+---+ +---+---+

Support profile:
^^ 1.2m ^^ ^ ^ ^ ^ ^

You need a support 'twixt the WM and TD, yes? How about this (which is
what I thought Tim meant but, judging by his reaction to your reply, it
wasn't) fabricate a "shelf bracket" from angle iron and flat strip, it
only needs to be 3mm thick steel, screw it _solidly_ to the wall at the
back of the worktop.

[T] Hi Parish, it was exactly what I had in mind for the middle of the
span but it turns out there is no space for such? I think Christian is
going to use the surrounding gear for the xbeam support at either end?

It will be more than strong enough. All you need is
3mm of space between the WM and TD, surely you must have that?

I couldn't draw it in ASCII art, so here's a quick CAD drawing of what I
mean. http://users.uk.freebsd.org/~mark/support.png

[T] The flat strip brace is fine where you have to sneak the bracket
into a thin gap. If it was 3mm thick and as wide as your drawing
suggests it shouldn't buckle under compression ;-)

All the best ..

T i m

On Tue, 24 Feb 2004 13:36:02 -0000, "Christian McArdle"
wrote:

I have some lengths of 50mm x 25mm x 1.5mm thick seam welded steel box
left over from when I built the garage doors. It's pretty stiff
(unlike angle) and probably stiffer than the support the cupboards can
provide?

25mm is, perhaps, a little too much, but pretty close. Although the
instructions call for 40mm wooden beam across the front, I am hoping that
doing several structs of metal 20mm will provide enough support.

I assume you wouldn't be able to take the box section along the entire
length of the worktop (this would provide more support?)

No. The next item is the dishwasher, which must be flush against the
worktop, unlike the washing machine and tumble dryer, which have the
facility to bolt the doors artificially high to cover the gap. Between the
dishwasher and tumble dryer is a stud framework with a pretty column pillar
on the front. The studwork is made of 47mm x 75mm softwood, so should
provide enough support for the metal lintels. I was planning to channel out
about 30mm for the lintel footings with a router.

[T] Ah, I see .. the reaon for the extended x bar is that it would be
supported by the box that is being held down by the granite eith side
of the span and helping to make the who lot 'stiffer' ?

All the best ..

T i m

p.s. I also have some (I think) 25 x 25 square box (like the
Speedframe stuff used for knock together workbenches) or some 20 x 15
x 1.5mm ? Will they take 5m lengths in the post?

All the best ..

T i m

[T] Ah, I see .. the reaon for the extended x bar is that it would be
supported by the box that is being held down by the granite eith side
of the span and helping to make the who lot 'stiffer' ?

Yes, I can see that would improve matters considerably. Unfortunately, the
dishwasher simply has to be next. Otherwise, the dishwasher would be next to
the Belfast sink, giving a stainless steel side slightly on display and
nothing to support the end of the granite section.

p.s. I also have some (I think) 25 x 25 square box (like the
Speedframe stuff used for knock together workbenches) or some 20 x 15
x 1.5mm ? Will they take 5m lengths in the post?

Hmmm. Approximately where in the country are you?

Christian.

Christian McArdle wrote:

So 20mm high will be enough to stop the Granite cracking when the
uninitiated decide to sit on the worktop? How many should I put across? I
was thinking of one near the front and one in the middle. The rear will be
held by some 2x3 softwood bolted to the wall.

Remind me - what's the span?


I should just squeeze 20mm in. I've got around 45mm absolute tops to play
with. 40mm would be safer, making it easier to insert/retract appliances and
less likely to end in tears. I can't lift the worktop another mm without
serious issues elsewhere.

I've got to get the beam, slate, tile adhesive and sealant in there then.
I've already got the 12mm ply down, so don't need to account for that.

That gives:

Adhesive 3mm
Slate 12mm
Beam 20mm
Sealant 5mm

That gives me exactly 40mm, so it should be OK, provided I spread adhesive
carefully.

I take it I can just run a thick bed of sealant and let it dry? I don't
think I want to glue the granite down? Is there a more suitable material for
this anyway, such as laying thin MDF/hardboard over the entire space?

I wouldn't worry about gluing the granite down - it'll peel off easily
enough.


--
Grunff

[T] The flat strip brace is fine where you have to sneak the bracket
into a thin gap. If it was 3mm thick and as wide as your drawing
suggests it shouldn't buckle under compression ;-)

I think I misread the original idea slightly, thinking of the bracket coming
from another angle.

The main problem with this solution is that it is next to impossible to
wiggle the washing machine in and out directly without borrowing the space
from the adjacent tumble dryer, which is itself so light it pushes in and
out with ease, giving the washing machine some room for manoevure.

If it is the only way to provide enough strength, then maybe I'll have to do
it, though, and pay for washing machine repair men to overcome the
installation/removal issues!

Do you think that 3 spans of 19mm box section would not be sufficient
support? If not, would the 25mm push it into acceptable territoriy?

i.e.

+-----------------------------
+-+-----------------------+-+-
| | | |
|###########################|
| | | |
|###########################|
| | | |
|###########################|
+-+~~~~~~~~~~~~~~~~~~~~~~~+-+

+----+
+----+ = 47mm wide, 75mm tall softwood

###### = 19mm box section stainless steel

~~~~~~ = decorative edged chipboard trim

Entire area inside of the softwood covered in thin MDF, flush with softwood
surface.

Christian.

Remind me - what's the span?

121 cm. Back edge and sides well supported.

Christian.

Christian McArdle wrote:

Remind me - what's the span?


121 cm. Back edge and sides well supported.

Then 20mm x40mm with 3mm wall will be fine - use 2 lengths - front and
middle.

--
Grunff

Christian McArdle wrote:

[T] The flat strip brace is fine where you have to sneak the bracket
into a thin gap. If it was 3mm thick and as wide as your drawing
suggests it shouldn't buckle under compression ;-)

I think I misread the original idea slightly, thinking of the bracket coming
from another angle.

The main problem with this solution is that it is next to impossible to
wiggle the washing machine in and out directly without borrowing the space
from the adjacent tumble dryer, which is itself so light it pushes in and
out with ease, giving the washing machine some room for manoevure.

If it is the only way to provide enough strength, then maybe I'll have to do
it, though, and pay for washing machine repair men to overcome the
installation/removal issues!


How often are you likely to need to pull the washing machine out? Not
very I expect. If you were to fix a brace like this with the angle iron
flanges on the TD side you could pull the TD out and remove the brace,
then put it back after the WM has been repaired/replaced. surely the
granite only needs supporting in case someone sits on it? It should
support it's own weight easily over a 1200mm span?

The advantage of a brace like that is that you can make it as deep as
you need to and making it totally rigid (for any conceivable load it's
likely to be subjected to) would not present a problem.

Regards,

Parish

Do you think that 3 spans of 19mm box section would not be sufficient
support? If not, would the 25mm push it into acceptable territoriy?

i.e.

+-----------------------------
+-+-----------------------+-+-
| | | |
|###########################|
| | | |
|###########################|
| | | |
|###########################|
+-+~~~~~~~~~~~~~~~~~~~~~~~+-+

+----+
+----+ = 47mm wide, 75mm tall softwood

###### = 19mm box section stainless steel

~~~~~~ = decorative edged chipboard trim

Entire area inside of the softwood covered in thin MDF, flush with softwood
surface.

Christian.

121 cm. Back edge and sides well supported.

Then 20mm x40mm with 3mm wall will be fine - use 2 lengths - front and
middle.

Obviously the 20mm is in the important vertical direction. Also, the metal
companies seem keen of "16" gauge, which they suggest is 1.5mm, rather than
3mm. Is this well underspecced? Does anyone publish formulae?

Christian.

Christian McArdle wrote:
121 cm. Back edge and sides well supported.

Then 20mm x40mm with 3mm wall will be fine - use 2 lengths - front and
middle.


Obviously the 20mm is in the important vertical direction.

I gathered that from your limited space.


Also, the metal
companies seem keen of "16" gauge, which they suggest is 1.5mm, rather than
3mm. Is this well underspecced? Does anyone publish formulae?

I wouldn't use 1.5mm wall for this.

I think you'll find it difficult to get a calculation on this - because
what you're aiming for is as close to zero deflection as possible. This
isn't normally calculated for. There has to be a certain amount of gut
feel/experience here. If you play around with some box section, you'll
soon see what I mean.

3mm walled box is easy to get hold of.

--
Grunff

3mm walled box is easy to get hold of.

Do you know where from?

The supplier I've found won't do anything smaller than 40mm x 40mm in 3mm. I
can get 20mm x 20mm with 2mm wall, but not rectangular box sections, only
square. Everything else only comes in 1.5mm or 1mm.

Christian.

On Tue, 24 Feb 2004 14:31:35 -0000, "Christian McArdle"
wrote:

The main problem with this solution is that it is next to impossible to
wiggle the washing machine in and out directly without borrowing the space
from the adjacent tumble dryer, which is itself so light it pushes in and
out with ease, giving the washing machine some room for manoevure.

[T] Gotcha ..

If it is the only way to provide enough strength, then maybe I'll have to do
it, though, and pay for washing machine repair men to overcome the
installation/removal issues!

[T] It's not 'strength' but 'stiffness' you need here though isn't it.
I think 3 spans would be sufficient as the rear and sides are solid. I
might put two near the front (where there is least supoport now) and
one down the middle.

Do you think that 3 spans of 19mm box section would not be sufficient
support? If not, would the 25mm push it into acceptable territoriy?

[T] I think the 'stiffness' goes up exponentially with the box
dimensions (that a guess not a scientific comment) so go as large as
you can. I'm pretty sure the tube wall thickness on my tandem cycle is
pretty thin and that takes all 16 st of me, and my not-ever-so-light
missus ok and without too much flex. (you need some in a cycle) ;-)

All the best ..

T i m (Nth London)

3mm walled box is easy to get hold of.

Also, what about aluminium? Is it much weaker than steel? It seems to
available in suitable sizes as solid bar or box sections. Not sure on price,
though.

Christian.

Christian McArdle wrote:
3mm walled box is easy to get hold of.


Also, what about aluminium? Is it much weaker than steel? It seems to
available in suitable sizes as solid bar or box sections. Not sure on price,
though.

If you went for aluminium you'd need solid bar to match the stiffness.
And it would cost *a lot* more.

--
Grunff

Christian McArdle wrote:

3mm walled box is easy to get hold of.


Do you know where from?

I have a place up the road that sells it - but delivery will be costly.

Look in yell for steel stockholders. There's bound to be one near you
who can supply.

--
Grunff

[T] It's not 'strength' but 'stiffness' you need here though isn't it.
I think 3 spans would be sufficient as the rear and sides are solid. I
might put two near the front (where there is least supoport now) and
one down the middle.

Yes, that sounds sensible.

Do you think that 3 spans of 19mm box section would not be sufficient
support? If not, would the 25mm push it into acceptable territoriy?

[T] I think the 'stiffness' goes up exponentially with the box
dimensions (that a guess not a scientific comment) so go as large as
you can.

Well, I'll try to get the 25mm in, although I can't be sure it will fit. It
would just be a case of deciding on a suitable really thin soft material to
lay over the top. Do you think a bead of dry sealant will be enough to
prevent the granite smashing due to the hardness?

Christian.

On Tue, 24 Feb 2004 15:36:53 -0000, "Christian McArdle"
wrote:


Well, I'll try to get the 25mm in, although I can't be sure it will fit.

[T] Lookat at a previous post 25mm sq would be ok?

It
would just be a case of deciding on a suitable really thin soft material to
lay over the top. Do you think a bead of dry sealant will be enough to
prevent the granite smashing due to the hardness?

[T] For me the 'problem' with a dry sealant is the difficulty you
would have getting a uniform thickmess?

I would fix all the things that were going to be fixed and then run a
strip of 1mm x 12mm double sided foam tape) around all the load
bearing edges of the things resting on the steel box, the wall plate,
the cabinet edges etc to absorb any movement etc? If they also need to
be waterproofed / sealed then add yer sealant afterwards ..

All the best ..

T i m

Christian McArdle wrote in message
...
Well, I've got a quote of 40 quid for enough 3/4" x 3/4" 16 gauge to span 3
times. That, I believe means 19mm x 19mm @ 1.5mm thick. Hopefully, this
will
be stiff enough to stop the Granite cracking.

If you pack the centre of the steel box section with a small
gravel/sand/cement concrete mix, you will find that the stiffness is
substantially increased. It's probably equivalent to a 3" thick granite
slab. I'd pack the gap between the steel box and the granite with something
like Unibond stone repair( sets like rock, 10 minutes max working life), to
ensure that the granite could not flex relative to the steel.

Regards
Capitol

On Tue, 24 Feb 2004 20:53:52 -0000, "Capitol"
wrote:


Christian McArdle wrote in message
...
Well, I've got a quote of 40 quid for enough 3/4" x 3/4" 16 gauge to span 3
times. That, I believe means 19mm x 19mm @ 1.5mm thick. Hopefully, this
will
be stiff enough to stop the Granite cracking.

If you pack the centre of the steel box section with a small
gravel/sand/cement concrete mix, you will find that the stiffness is
substantially increased. It's probably equivalent to a 3" thick granite
slab. I'd pack the gap between the steel box and the granite with something
like Unibond stone repair( sets like rock, 10 minutes max working life), to
ensure that the granite could not flex relative to the steel.

Are you sure about that? Granite is not going to flex at all, so
fixing it with an adhesive that has no give to something that might
but shouldn't doesn't seem intuitively right to me.



..andy

To email, substitute .nospam with .gl

"Christian McArdle" wrote in message
. net...
In this episode of my granite fitting saga, it appears that there won't be
enough room for the 40mm wooden beam across the twin appliance gap to
support the granite. What width steel box section would have the same
bending resistance as the 40mm wood specified?

Also, can granite rest directly on the metal, or should there be a soft
material on top, such as hardboard?

Christian.



If you're having difficulty sourcing the box section, what about a few runs
of angle iron to support? With a suitable facing if any of it is on show,
of course....

--
Richard Sampson

email me at
richard at olifant d-ot co do-t uk

In article , Andy Hall
wrote:
Are you sure about that? Granite is not going to flex at all, so
fixing it with an adhesive that has no give to something that might
but shouldn't doesn't seem intuitively right to me.

If it doesn't flex at all then the steel is redundant as it must
deflect by some (minuscule) amount if it is carrying a proportion of
the load. If the granite just bears on the steel you'll have a load
sharing situation. If you fix the steel to the granite with epoxy or
whatever and put weight on the granite it will be in compression and
the steel in tension like a RC beam.

--
Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk
Free SEDBUK boiler database browser http://www.sda.co.uk/qsedbuk.htm

On Wed, 25 Feb 2004 11:39:34 GMT, Tony Bryer
wrote:

In article , Andy Hall
wrote:
Are you sure about that? Granite is not going to flex at all, so
fixing it with an adhesive that has no give to something that might
but shouldn't doesn't seem intuitively right to me.

If it doesn't flex at all then the steel is redundant as it must
deflect by some (minuscule) amount if it is carrying a proportion of
the load. If the granite just bears on the steel you'll have a load
sharing situation. If you fix the steel to the granite with epoxy or
whatever and put weight on the granite it will be in compression and
the steel in tension like a RC beam.

Makes sense. Since the steel, I would have thought would flex rather
more than the granite, I would expect that the granite would crack.
Unless I've missed something?



..andy

To email, substitute .nospam with .gl

"Andy Hall" wrote in message
...
On Wed, 25 Feb 2004 11:39:34 GMT, Tony Bryer
wrote:

In article , Andy Hall
wrote:
Are you sure about that? Granite is not going to flex at all, so
fixing it with an adhesive that has no give to something that might
but shouldn't doesn't seem intuitively right to me.

If it doesn't flex at all then the steel is redundant as it must
deflect by some (minuscule) amount if it is carrying a proportion of
the load. If the granite just bears on the steel you'll have a load
sharing situation. If you fix the steel to the granite with epoxy or
whatever and put weight on the granite it will be in compression and
the steel in tension like a RC beam.

Makes sense. Since the steel, I would have thought would flex rather
more than the granite, I would expect that the granite would crack.
Unless I've missed something?



yes, I think you've missed something in this.

The granite will break not because of the compression it suffers at the top
but due to it's weak tensile strength on the underside.

If you bond steel section firmly to the underside it gives the granite the
required tensile strength and therefore prevents the breakage.


The alternative is to provide a firm inflexible support for the granite and
not bond it securely. You limit the amount that the granite can deflect and
hence the maximum tension that it will suffer underneath. This would mean
that any flexible bedding or sealant used between steel and granite must be
as thin as possible, because this would allow slight movement.


One thought that does strike me relates to the expansion of the steel with
heat and whether the firmly bonded solution would be problematic in this
instance. Might the heat kicked out from the WM and TD be sufficient to
cause problems with this? (thinking aloud here, the granite ought to
provide a good thermal sink thus preventing the steel from heating up and
therefore expanding too much).


--
Richard Sampson

email me at
richard at olifant d-ot co do-t uk

On Wed, 25 Feb 2004 13:58:38 -0000, "RichardS" noaccess@invalid
wrote:

"Andy Hall" wrote in message
.. .
On Wed, 25 Feb 2004 11:39:34 GMT, Tony Bryer
wrote:

In article , Andy Hall
wrote:
Are you sure about that? Granite is not going to flex at all, so
fixing it with an adhesive that has no give to something that might
but shouldn't doesn't seem intuitively right to me.

If it doesn't flex at all then the steel is redundant as it must
deflect by some (minuscule) amount if it is carrying a proportion of
the load. If the granite just bears on the steel you'll have a load
sharing situation. If you fix the steel to the granite with epoxy or
whatever and put weight on the granite it will be in compression and
the steel in tension like a RC beam.

Makes sense. Since the steel, I would have thought would flex rather
more than the granite, I would expect that the granite would crack.
Unless I've missed something?



yes, I think you've missed something in this.

The granite will break not because of the compression it suffers at the top
but due to it's weak tensile strength on the underside.

If you bond steel section firmly to the underside it gives the granite the
required tensile strength and therefore prevents the breakage.


The alternative is to provide a firm inflexible support for the granite and
not bond it securely. You limit the amount that the granite can deflect and
hence the maximum tension that it will suffer underneath. This would mean
that any flexible bedding or sealant used between steel and granite must be
as thin as possible, because this would allow slight movement.


I see what you're saying.


One thought that does strike me relates to the expansion of the steel with
heat and whether the firmly bonded solution would be problematic in this
instance. Might the heat kicked out from the WM and TD be sufficient to
cause problems with this? (thinking aloud here, the granite ought to
provide a good thermal sink thus preventing the steel from heating up and
therefore expanding too much).

So it seems that the conclusion is not completely clear - one can
argue either way




..andy

To email, substitute .nospam with .gl

Andy Hall wrote in message

Unless I've missed something?

Yes, filling the steel section with concrete gives you a reinforced concrete
lintel, just turned inside out!
As I said, to get the optimum effect, the granite needs to be bonded to the
"concrete lintel" which corresponds to about a 3" thickness of granite IMO.

Regards
Capitol