Filling gaps in exterior wooden doors


RESIN AND WOOD DUST Most 
professional floor sanders use different methods to fill the gaps between the floor boards. The method most widely in use is a resin filler mixed with wood dust creating a thick paste that is applied with a spatula. I use this method only where the strip method cannot be used, as with parquet floors and wood block. With floor boards , if you aren't too worried about how long you want this filler to last, this method will be ok for you, but (and there is a big but ) all resin eventually shrinks and with boards, your filler either ends up in the vacuum cleaner dust bag or falls through into the space below the boards, leaving you once again with unsightly black gaps and a lot of draught. If you use this method for boards, use the best quality resin. We use Lecol filler where this method of filling is the only alternative, or with wood block and parquet floors where the filler cannot fall through anyway. STRIP METHOD FOR BOARDS ONLY 
In the case of floor boards, I use a method that involves cutting strips of Hardboard and or MDF, which is then glued in the gap, but also sits on the joists, so can't fall through. This method, when done properly, is by far the best, lasts by far the longest and is visually the most pleasing of all finishes to look at.
When applying the strip method: 
1. Do not use a conventional hammer to work the strip into the gap. This will damage the strip and board. 
2. Do not use a chisel to work down the raised top of the strip. This will tear the strip and could damage the board.
 Which ever method you use, the filling is always done before the sanding as the sanding smoothes and flattens the whole surface ready for the varnish. Hope this helps.

Hi, i personally would use something called two pack filler which is a two part filler which is very hard wearing and solid. I would be very careful when mixing this product as you don't put too much hardener in so that you don't have time to work with it, but also make sure there is enough hardener in. Don't fill the hole like you would fill a hole with normal filler leaving it all proud as you will have great difficulty rubbing it down as i found out the hard way when i was an apprentice .