External window sill replacement (concrete)

[alextee]

well i am replacing a few concrete window sills for a friend which have cracked and crumbled.

when i have cleaned off the old cement should i cement some sort of DPC down before bedding the new sill?

have asked a few people and got different answers so im a bit confused.

also, i wanted to remove and replace the sill WITHOUT taking the window out, the window is quite large and i dont really want to make the job longer if i can help it.

BUT the window looks like its sitting on top of the old sill. how should i go about removing it safely so that i dont damage anything else?

thanks
...
it looks something like this (only a lot bigger and broken and crumbled)
its the second image:
https://www.google.co.uk/search?sug...A&biw=1366&bih=653&sei=6LXnT86YD8Sh0QXcjJipDQ

 

[Alastairreid]

You will have to cut pockets out either side of the cill, clear any silicone, mastic etc between window and cill.
Use bolster chisel below cill and rotate up and out.

The window shouldnt go anywhere.

 

[alextee]

You will have to cut pockets out either side of the cill, clear any silicone, mastic etc between window and cill.
Use bolster chisel below cill and rotate up and out.

The window shouldnt go anywhere.

surely i cant remove a sill from underneath a window and then slide the new one under it where the old one was???

 

[Alastairreid]

The window should be fixed both sides and on the head, i have renewed hundreds of cills over the yrs never once having to remove the window.

 

[cotswoldbuilders]

Do as Alastair said, you will have a bit of play when you clean the bed joint out.
Prior to refitting you can slide some dpc in, lap it against inner wall.
When the cills in, wedge it up tight to frame then pack tight underneath.
Use a small tool or jointer to push the mortar in tight.

 

[vv2806]

Guys, thank you for the topic and the advice. I am not the OP but have to change a rotten timber under a sliding patio door. Hope the same technique will do.

 

[Alastairreid]

No sorry different scenario from a structural cill/sill ....yours will most likely be screwed to the frame which would require the removal of the doors .
Unless someone knows an easier method.

 

[vv2806]

Yes, it occurred to me after I posted the comment that it would be screwed to the timber underneath as well