What to cover underside of stairs?

Hi there. The underneath part of our staircase is currently bare.

When i've fixed the creaking in the next day or so, I may as well board it up too, but unsure what to use.

I will probably paint it white if that makes a difference, but I've got a few queries.

What wood should I use, or plasterboard?

How do I finish the edge off?

As you can see from this picture:



if i put board right to the end, you would see that?

Heres a few other pics:





Thanks for the help

There are a number of options.
You could use plasterboard and skim. Commonly done but you will have to consider the mess and it's a wet trade. The edge would be finnished with an architrave of some kind.
Personally in this case I would go for mdf. A 1/2" sheet with a moulding routered down the outside edge where it abuts the string. That just leaves the screw holes to make good and then paint.
Fireproof mdf is available if you're worried about any risk of that type, it's the red type. I'veused this method in a couple of places in my own house to good effect.

Thanks for the reply ladylola.

That sounds a good suggestion and I may well do that. Do you have any pics of the ones you have done? Just looking for inspiration.

Cheers

An example of what I'm talking about.
The first shows the finish at the rear of our property. There was an extenstion in place but it was frankly poor, full lenght single pane glass to the floor and the cills were begining to rot. I replaced with brick work to waist height,made and put in the patio doors added double glazing and finished as you can see. I went down the mdf route as it made life easier, I didn't really want the wet trades in the house, we had a small daughter and so.
The vertical strip to the right of the corner is purely a decorativefeature that is repeated elseware and the corners are finished off with 1/2" dowel picked out in white.


The second shot shows how the same process was done to a exsisting nib to add detail.

just come across this post, have you got any pictures of how you got the underside of your stairs looking? I'm looking at taking out our understairs cupboard and having it all open and could do with looking at how to board the underside of the stairs up.

thanks