How to repair timber floor after removing door jambs?

[elbow]

Hey Guys

I am removing old wooden door jambs and re-sanding my floorboards - However, as you can see, where I have removed the door frame, I am left with a hole in my floorboards each side. In the hole there is some concrete which i assume are foundations. When i replace the skirting i think about half of these holes will still be showing. What would you suggest i can do to fill the holes?  any suggestions are very much appreciated -  

[JacobZ]

Hi @elbow,

Thank you for your question about filling some gaps in your floorboards where a door jamb was removed.

The only solution I see is to remove the cracked mortar/concrete, slip a piece of timber underneath the existing floorboards to bridge the gap, screw through the existing floorboards into that piece of timber to lock it in place and then put a piece of timber into the gap that is the same thickness as the floorboards. This will finish the flooring at the same height as the existing stuff, which we can then stain and varnish as closely as possible to its surrounds.

If you had a spare floorboard anywhere, this would be ideal, but if you don't, can you advise how thick the floorboards are so I can recommend a suitable timber for this?

Can you also let me know how much of a gap there is underneath the floorboards once the cracked concrete/mortar has been removed so I can recommend a timber to act as a back block?

Let me know what you think.

Jacob

[elbow]

Hey Jacob, thanks for coming back, 

Seems like a reasonable suggestion. I've  added another pic for clarity and better angle. No spares anywhere unfortunately. The board thickness is 22mm and the gap underneath the board to the concrete is 25mm