How would you fix this?

[FluidDruid]

House looking at putting an offer on - wood at the bottom of the patio door looks rotten and step is weird, didn't look planned to be the way it is if that makes sense. If we needed to replace the wood, would this be a big job?

To do this repair correctly, yes, it’s a big job the patio doors need to come out and the cil replaced preferable with plastic, I would estimate a joiner with a laborer could do this in a day (rough estimate based on one photo). You could cut away the rotted front section then glue and screw a piece on. Depends how far the rot has gone and TBH even the best attempted would only last a couple of years and could still take all day. The step is a completely separate job, looks like you have the depth to replace the step and set it on a bed of mortar that would sit on the concrete, but again to do it right the concrete needs to be removed and a new subbase put down.

I'd get rid of that silly step and have some decking put there going right up to the patio door.

I agree with @Slawit it’s an involved job to do properly, and there’s no point not doing it properly in a high traffic area.
The height of the patio cannot be altered, as it’s already only just low enough. You can see the air bricks are only one course above it.
The step (looks like an afterthought, probably to stop the kids tumbling out the door) is a simple job to improve. It should be deeper and wider. Not really a negotiation point mind.
They have painted the brickwork, usually not a great idea, and comes up in a survey if they didn’t stop at the dpc level.

I’d probably just try and repair it by sanding it, filling and then repainting, making sure it’s protected from water. It would be a yemporary fix. Then I’d build a proper step.

@HellsBalls thanks for the response. I would definitely fix it properly rather than bodge it as it's high traffic. Any thoughts on a ballpark figure for cost?

Didn't pick up on the patio being so close to the damp course.

The concrete is cracked across the patio as you can see and then grass. Is this anything to be concerned about? It doesn't look great but not concerned if it's not a potential problem.

cills can be replaced. They can be bought or made in hardwood or softwood. The old rotten one is cut off and the new one glued/screwed in. Then painted. It's a perfectly acceptable solution (if you like the door). Door steps can also be replaced. I would say it's a fairly small job, but not trivial.

The DPC is usually right on top of the air brick, right underneath the door. So in your case, the minimum 150mm between ground level and dpc is just about met.
Those are slabs, not concrete, so nothing to worry about. A pressure wash will improve their appearance.

You can’t/shouldn’t just get the cill chopped off and replaced with another wooden one because it’s high traffic, people will be treading on it, so it will just pull off. That method can be a viable method for windows, not doors, in my opinion.

Cost I don’t know. As per @Slawit a days work for 2 people. They need to remove the doors, remove the glass panes, unbolt the frame and remove it, knock out the wooden cill, place the new cill, reassemble, reseal. Not much cost in materials. For a local company maybe £1000 to £1200 at a guess? For the step half a days labour, low material cost. Typical DIY Saturday job.

@HellsBalls this is so helpful, really appreciate it, thank you.