I'm in the middle of replacing the sill section of a bay window. I've
knocked out the hole sill which cold bridged straight through.

I've replaced this with 2" aerated block as you can see and have started the
form work to cast a new sill.

http://tinypic.com/view/?pic=2uj46m9

http://tinypic.com/view/?pic=4dcijcj

Now what would you do? As you can see, I have to avoid filling the cavity in
the close up, and I have to not reinstate the cold bridge, so some sort of
insulation between sill and blocks? Also I have not much depth to play with
as you can see the window frame does not overhang by much, but I'll probably
glue a weather bar along it. Does a DPC need to go in somewhere? I believe
you usually fit a cavity tray kind of thing that is tucked into the top of
my thermal blocks but this is custom and I won't find the right size. I can
put 1200 DPC in somewhere - upturned against the blocks?
Suggestions welcomed.

--
Mike W

VisionSet wrote:

I'm in the middle of replacing the sill section of a bay window. I've
knocked out the hole sill which cold bridged straight through.

I've replaced this with 2" aerated block as you can see and have started the
form work to cast a new sill.

http://tinypic.com/view/?pic=2uj46m9

http://tinypic.com/view/?pic=4dcijcj

Now what would you do? As you can see, I have to avoid filling the cavity in
the close up, and I have to not reinstate the cold bridge, so some sort of
insulation between sill and blocks? Also I have not much depth to play with
as you can see the window frame does not overhang by much, but I'll probably
glue a weather bar along it. Does a DPC need to go in somewhere? I believe
you usually fit a cavity tray kind of thing that is tucked into the top of
my thermal blocks but this is custom and I won't find the right size. I can
put 1200 DPC in somewhere - upturned against the blocks?
Suggestions welcomed.

I would have thought a can of expanding PU foam would be your friend
here! Fill the top of the cavity, and the the gap under the frame. Once
set, trim with a saw to your required levels, then shutter up your
casting and pour away.

--
Cheers,

John.

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

"John Rumm" wrote in message
...
VisionSet wrote:

I'm in the middle of replacing the sill section of a bay window. I've
knocked out the hole sill which cold bridged straight through.

I've replaced this with 2" aerated block as you can see and have started
the
form work to cast a new sill.

http://tinypic.com/view/?pic=2uj46m9

http://tinypic.com/view/?pic=4dcijcj

Now what would you do? As you can see, I have to avoid filling the
cavity in
the close up, and I have to not reinstate the cold bridge, so some sort
of
insulation between sill and blocks? Also I have not much depth to play
with
as you can see the window frame does not overhang by much, but I'll
probably
glue a weather bar along it. Does a DPC need to go in somewhere? I
believe
you usually fit a cavity tray kind of thing that is tucked into the top
of
my thermal blocks but this is custom and I won't find the right size. I
can
put 1200 DPC in somewhere - upturned against the blocks?
Suggestions welcomed.

I would have thought a can of expanding PU foam would be your friend
here! Fill the top of the cavity, and the the gap under the frame. Once
set, trim with a saw to your required levels, then shutter up your
casting and pour away.


Ah yes, that would be perfect for the irregular void at the end of the sill,
but against the thermal blocks, I'd rather use a thin sheet material - like
10mm. What comes that thin that would be suitable - I only need 0.5sqm.
Preferably free! I hate that foam stuff, so messy.

--
Mike W

Don't forget a half dowl along the timber base to form a drip grove
in the bottom.

--
Andrew Gabriel

On Tue, 05 Sep 2006 21:07:19 +0000, Andrew Gabriel wrote:

Don't forget a half dowl along the timber base to form a drip grove
in the bottom.

Well no I won't but does it really matter if you do forget. An angle
grinder with a worn stone grind disk will easily put one in with a simple
guide. In the past I've cast them with a section of flex cable clipped to
the bottom of the mould.

--
Mike W

On Tue, 05 Sep 2006 15:56:55 +0000, VisionSet wrote:

Does a DPC need to go in somewhere? I believe
you usually fit a cavity tray kind of thing that is tucked into the top of
my thermal blocks but this is custom and I won't find the right size. I can
put 1200 DPC in somewhere - upturned against the blocks?

This is the bit I'm most interested in opinions on...

--
Mike W

visionset wrote:
On Tue, 05 Sep 2006 15:56:55 +0000, VisionSet wrote:

Does a DPC need to go in somewhere? I believe
you usually fit a cavity tray kind of thing that is tucked into the
top of my thermal blocks but this is custom and I won't find the
right size. I can put 1200 DPC in somewhere - upturned against the
blocks?

This is the bit I'm most interested in opinions on...

Affix a DPC in an L shape against the thermalite before you do anything
else, any water that goes behind whatever cill you decide to add will run
under the sill and away, provided you leave drain holes, TBH it's not
imperative as the joint between window frame and cill will surely be sealed
with plastic / silicone / beading / whatever.....unless you are thinking
about damp 'penetrating' the concrete and into the thermalite?

On Tue, 05 Sep 2006 21:52:57 +0000, Phil L wrote:

This is the bit I'm most interested in opinions on...

Affix a DPC in an L shape against the thermalite before you do anything
else, any water that goes behind whatever cill you decide to add will run
under the sill and away, provided you leave drain holes, TBH it's not
imperative as the joint between window frame and cill will surely be sealed
with plastic / silicone / beading / whatever.....unless you are thinking
about damp 'penetrating' the concrete and into the thermalite?

Thanks Phil, I won't bother then.

--
Mike W

visionset wrote:


Well no I won't but does it really matter if you do forget. An angle
grinder with a worn stone grind disk will easily put one in with a simple
guide. In the past I've cast them with a section of flex cable clipped to
the bottom of the mould.

Sash cord works well too.

--
Cheers,

John.

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