Rotten exterior door frame - do i need a sill?

[edtea]

I've had to take out about 12 inches of my back door jambs because of rot and wood worm.
The jambs were basically sitting in the soil.

I'm going to replace the rotten pieces but I wonder do I need to but in a (wooden) sill under the jambs?

There isn't one at the moment, but there is a sort of then concrete threshold in between where the jambs finished.

Also, what should I treat the new pieces with and how can I stop the rot coming back?

Thanks very much in advance.

 

[pinenot]

When you'r replacing the rotted sections of jamb(s) get some (wide) dpc tucked in behind them before fixing. Cut the existing jamb end at an angle to provide a water shedding angle to the joints and allow the dpc to trail out at right angle to the door slap ends. Fit your replacement pieces, suitably angled to match ex jamb loading both ends with Paint/varnish or whatever, to provide a good joint seal, which will be impervious to moisture (hopefully for ever) The length of the replacement jamb sections should be snug, not tight, and the wide dpc can be cut to allow 6mm to stick out the sides and bottom when all is fixed, this should be fully covered with a polysulphide (color of your choice) once all the re-decoration is complete. This should provide you with a sound waterproof repair and all that remains is to try and drain the area affected against future problems...pinenot

 

[edtea]

Thanks very much for the reply. That all makes a lot of sense. One last question: If the new jamb parts are fully waterproofed etc is it ok for them to sit on the existing concrete sill or should I put in a new timber sill with the appropriate grooves underneath to allow rainwater to flow away?

Thanks again.

 

[pinenot]

With the turned out dpc in place between the replacement pieces end grain, and the concrete fully sealed with polysulphide, I can see no reason to replace the cill...pinenot

 

[edtea]

Thanks pinenot. Woodwork all sorted now and looking good.
I've been recommended to paint with sikkens. I'm told this is the best stuff.
I'll go ahead unless someone says whatever you do don't paint with sikkens!

Thanks again for all your help.

 

[pinenot]

Sikkens is an excellent choice in my opinion...pinenot