outside wooden window sill on a leanto

24 Apr 2008
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UK, Wittering, West Sussex
United Kingdom
I built a leantoo in 1996 built out of wood
small course of bricks at the bottom
then half height tongue and groove
then a big window sill bit of timber
and windows and doors

The window sill timber was treated and used duckback a green colour and lasted well upto about 2010 and started to show wear and the finish cracking and peeling , mainly on the sill

in 2012 I rubbed all the sill down - its a right angle - about 60" on one side and 12ft on the other
Then I used wood hardener on all the soft wood and the cracks and filled with wood filler (the type you mix up a golf ball of a filler and a pea of hardener

then I think we used a green saddling on it to finish it all off

I did this in the late summer of 2012 , well by end of summer 2013 its all peeling again and cracking

whats the best way to fill the cracks and treat the wood
I cannot replace as its part of the structure of the leantoo
and holds all the windows and upright frames for the roof

the rest of the wood on the tongue and groove and all the uprights are still OK

its just the sill where it gets a lot of water coming down large glass pains
onto it

thanks for any help and advice
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You could try sadolin superdec, it's very hard wearing, it's what they use on beach huts!, once you have made the sill sound, it is self undercoating, but it is an opaque finish.

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