Hi all

I have made a cover for some box work out of MDF and tiled the top.
Unfortunately it looks like the adhesive action has caused the cover to bow.
Guess I should have applied weights to hold it flat while the adhesive went
off .
If I weight the cover is such a way to reverse the bowing, will this reverse
the process, or will it just re-bow in time?

TIA from a newbie wood-worker

Phil

On 2007-07-31 09:14:15 +0100, "TheScullster" said:

Hi all

I have made a cover for some box work out of MDF and tiled the top.
Unfortunately it looks like the adhesive action has caused the cover to bow.
Guess I should have applied weights to hold it flat while the adhesive went
off .
If I weight the cover is such a way to reverse the bowing, will this reverse
the process, or will it just re-bow in time?

TIA from a newbie wood-worker

Phil

Do you mean ceramic tiles, Phil?

If so, ply is likely to be a better substrate

"TheScullster" wrote in message
. uk...
Hi all

I have made a cover for some box work out of MDF and tiled the top.
Unfortunately it looks like the adhesive action has caused the cover to
bow.
Guess I should have applied weights to hold it flat while the adhesive
went
off .
If I weight the cover is such a way to reverse the bowing, will this
reverse
the process, or will it just re-bow in time?

TIA from a newbie wood-worker

Phil



If the cover is not going along the sides of the boxwork ie not resting on
the top of them? it will bow with the weight of the tiles and will not
flatten out.
If the cover is thin? it still will not flatten out for the weight of the
tiles, will bow it.

On Tue, 31 Jul 2007 10:13:20 GMT, "George"
mused:


"TheScullster" wrote in message
.uk...
Hi all

I have made a cover for some box work out of MDF and tiled the top.
Unfortunately it looks like the adhesive action has caused the cover to
bow.
Guess I should have applied weights to hold it flat while the adhesive
went
off .
If I weight the cover is such a way to reverse the bowing, will this
reverse
the process, or will it just re-bow in time?

TIA from a newbie wood-worker

Phil



If the cover is not going along the sides of the boxwork ie not resting on
the top of them? it will bow with the weight of the tiles and will not
flatten out.
If the cover is thin? it still will not flatten out for the weight of the
tiles, will bow it.

Sounds like it has bowed in the opposite direction to which you think
it has.
--
Regards,
Stuart.

"George" wrote


If the cover is not going along the sides of the boxwork ie not resting on
the top of them? it will bow with the weight of the tiles and will not
flatten out.
If the cover is thin? it still will not flatten out for the weight of the
tiles, will bow it.

Sorry fellas

Yet another poor explanation of the situation!
The cover forms the top of the boxwork and sits flat (horizontal) - approx
dimensions 700 x 210 and is supported underneath all four edges.
It is made from 12 thick MDF with a 20 x 9 frame on top around ceramic wall
tiles.
Tiles stuck in place with Bal White Star.
I had laid the cover in position for the adhesive to dry, but the ends have
"curled up".
I have now turned the cover upside down, supported each end and sat a box of
photographs on the "back" to try to straighten it.
I didn't use ply as the edge of the board is visible.

Phil

TheScullster wrote:
"George" wrote

If the cover is not going along the sides of the boxwork ie not resting on
the top of them? it will bow with the weight of the tiles and will not
flatten out.
If the cover is thin? it still will not flatten out for the weight of the
tiles, will bow it.

Sorry fellas

Yet another poor explanation of the situation!
The cover forms the top of the boxwork and sits flat (horizontal) - approx
dimensions 700 x 210 and is supported underneath all four edges.
It is made from 12 thick MDF with a 20 x 9 frame on top around ceramic wall
tiles.
Tiles stuck in place with Bal White Star.
I had laid the cover in position for the adhesive to dry, but the ends have
"curled up".
I have now turned the cover upside down, supported each end and sat a box of
photographs on the "back" to try to straighten it.
I didn't use ply as the edge of the board is visible.

Phil



You could drill through the tiles and bung some mirror screws in. Best
to wait a couple of days for the adhesive to dry completely.
I must say I've never had this problem with 12mm mdf

On Jul 31, 11:37 am, "TheScullster" wrote:
Yet another poor explanation of the situation!
The cover forms the top of the boxwork and sits flat (horizontal) - approx
dimensions 700 x 210 and is supported underneath all four edges.
It is made from 12 thick MDF with a 20 x 9 frame on top around ceramic wall
tiles.

Hi,

Is there framing attached to the MDF itself? This should minimise
bowing, but it needs to be much thicker than 9mm.

It sounds like you tiled straight onto bare MDF which may have caused
the surface under the tiles to swell and then shrink.

cheers,
Pete.

"Pete C" wrote

Is there framing attached to the MDF itself? This should minimise
bowing, but it needs to be much thicker than 9mm.


Only cosmetic framing around the outside of the tiled area

It sounds like you tiled straight onto bare MDF which may have caused
the surface under the tiles to swell and then shrink.

Yes I did tile straight on, but have found that applying PVA to MDF or ply
results in a similar bowing effect.
There is still the grouting operation to contend with - might make matters
even worse :-(
I was hoping to have a simple lift-off top for the boxing to gain access to
the toilet cistern below. Otherwise the chrome top screws would have been
an option.
I have fitted a plastic lid of sorts to the cistern to prevent moisture
hitting the underside of the cover (even though the cover is painted
underneath).

Phil

On Jul 31, 2:41 pm, "TheScullster" wrote:
"Pete C" wrote

Is there framing attached to the MDF itself? This should minimise
bowing, but it needs to be much thicker than 9mm.

Only cosmetic framing around the outside of the tiled area

If some 1" or bigger planed batten is clamped and glued underneath it
might straighten it out. It shouldn't need to be right up to /on to
the edge either.


It sounds like you tiled straight onto bare MDF which may have caused
the surface under the tiles to swell and then shrink.

Yes I did tile straight on, but have found that applying PVA to MDF or ply
results in a similar bowing effect.

Maybe putting PVA on both sides would minimise the effect. Or better
still use a sealer that isn't water based.

cheers,
Pete.

"Pete C" wrote

If some 1" or bigger planed batten is clamped and glued underneath it
might straighten it out. It shouldn't need to be right up to /on to
the edge either.

Yes I had considered additional webs, but the cover is heavy enough as it
is!
I can see SWMBO trying to lift it off and dropping it/smashing the loo seat
:-(.
Guess I'll give it a day or two with the weights on and see if it holds
shape

Thanks

Phil