windowsill construction

[VisionSet]

I have to repair some window sills right through exterior to interior decorated surface. The window is a 6 facet bay of soft wood timber that I shall retain due to budget and aesthetics. The sills were straight through

1 piece cold bridging concrete but have disintograted, so I shall likely recast in situ. I have just 8 inches of brick depth to play with (2 skins of standard clay 4inch brick and no cavity). I won't remove the windows. There will be 40mm insulated p.board internally to finish. What is the construction method I should use with these givens? DPC? seal to lower edge of window frame? Links to construction diagrams would be great!

TIA, Mike W

[Italian Mason]

[VisionSet]

Yes essentially. Though I have some idea, I just want to make sure (naturally) I do right. DPC = damp proof course, I expect this is a cavity tray, though retro fitting one I expect I might as well give up now finding suitable dimensions off the shelf, the blue 1200? guage poly liner I expect is suitable? Stainless or galvanised reinforcing or is it really neccessary? And can I cast the piece in one piece, this will be 4 metres long on a curving bay. To get a goof finish on cast concrete the mix should be a wet than usual, but I need to finish the top surface with a fall, getting the mix the right consistency to do both might be hard.

-- Mike W

[Italian Mason]

Rebar is necessary but neither of the above is, standard steel is fine. Carefull on the water... if you are concerned about the appearance you can always go back and "face" the exsposed areas with a sand and cement mixture. if you really want a smooth appearance line the forms with plastic sheeting and pour into these++++CAUTION++++ DO NOT DO THIS ON A WARM DAY as plastic accelerates the process greatly. after you have the forms filled using a palm sander place a stick of good size or even a leftover piece of rebar into the concrete and place the sander on the bar (move this around to different places in the form) this will vibrate the mixture removing air and making the form voids fill completely...just dont over do it or all the rock will fall to the bottom..

Visi>