window sil in sash window

I have an 1880 sash window with a rotten bottom sil how do I replace it? Can it be done with out removing the window from the wall? I have thought of filling it with bog or patching with fibre glass any ideas would be good.

I take it you mean a circa 1880 sash window - not one that is 1880 mm tall???
The answer is - how good a job do you want. If you just want to make it look OK for a year or two bog, fibre-glass etc. would do but not for long. The rot will continue and whatever you use will fall off or out.
Actually, once you take the architrave off you will find it is not too difficult to remove. You will have to remove the entire window to do the job properly. I presume it is a box frame (it has weights). You will need to check the frame where it is in contact with the sill to be sure that the rot has not spread to it. If it has you will have to replace the entire frame.
Your biggest difficulty will be obtaining a new sill of the correct dimensions - that is if you have not got the gear to mill your own. It doesn't have to be the correct thickness, you can always put some packing under it, but the other dimensions have to match. In 1880 sashes were usually thicker than today.
Sometimes it is easier to make an entire new window paticularly if the sashes are a bit past their use by date.
Making a box frame window is great joinery practice(!!) and these days you can buy all the matching mouldings.
As is obvious, I wouldn't advise the patching process, but then, it all depends on for how long you want it to look good.
Cheers

Thankyou Geoffs when the weather settles down a bit I'll have a go at pulling it out. I hope I don't have to build a new one.
Glenn

Hey Glen
I have lots of sash windows in my place . Some were rotten but I was able to replace the rotten bit. The inside sill on my bathroom window was simply a piece of 40mm square timber that was rounded on one side it was nailed to the sill with three two inch nails. I simply replaced it. If your outside sill is crook you may be able to cut it off flush with the wall and make a new face piece for it, but if the timber you try to join it to is rotten you'll have trouble. Good luck, you'll see once you have it apart.
cheers
Jim

try a boatbuilding supplier. i remember reading about a product that is brushed on. it soaks into the rot and kills it, then sets to form a solid surface on which a filler can be applied. if it can withstand a marine environment it should last quite a while on a window.
checkout a copy of Australian Amateur Boatbuilder magazine, they have ad's for companies all around Oz, and it's a very interesting read as well!!

good luck.

It is more than the outside Hovo
Thanks re do 4 u I live in Williamstown we have heaps of boat builders here I will go ask one or two thankyou