Digging out slab - remove stairs?

[haythorn_1]

As part of a renovation I am going to dig out the old concrete slab of my house so I can replace it with a new build up of insulation and concrete.

 

The area to dig out includes a staircase so I have been debating whether it is worth removing it so I can completely dig out under it or do I just excavate as best I can around it.

 

If I leave it in place then there will certainly be a couple of cold bridges.

 

Clearly the optimum way would be to remove it but is it worth the cost of replacing the staircase?

[Conor]

You could probably remove everything while leaving it in place. Take a bit out, prop it up, take the rest of it out, prop it up. Reverse the process when putting insulation down.

[haythorn_1]

And then leave the props in when pouring the concrete? So they are cast in place?

 

I did wonder whether I could support it from above.

[haythorn_1]

Although was just having a quick look on stairbox and a replacement staircase is ~£800. So not terrible.

[Russell griffiths]

Cut the bottom two treads off, prop the stairs and make a plywood box for temporary access 

chuck the plywood box outside while you dig and concrete. 
when repairing the stairs you could re shape the bottom two treads to give you a nice big bull nose bottom step or something like this. 
 

I bought a new staircase and purposely made it two stairs high so I could tile under it and we hadn’t decided if to have a bull nose bottom step or more modern square look. 

[torre]

When we did this, to keep the stairs as is we excavated to the edges and then added an insulated upstand to minimise cold bridging to the rest of the floor. Below our stairs is only cupboard space, if we ever clear it out we'll probably add a layer of rigid insulation and a false floor

[saveasteading]

How much heat flow would there be through that area? If near an outside wall then perhaps it is significant. Centrally probably not.

 

In such quandaries, I draw a cross section, then arrows of the heat loss.

Usually you can block or hinder these paths.

Earth is a half decent insulator under a slab, when away from outside walls. The insulation manufacturers used to acknowledge this.

[torre]

3 hours ago, saveasteading said:

How much heat flow would there be through that area? If near an outside wall then perhaps it is significant. Centrally probably not

 

Ours was an outside wall so I agree quite significant loss, but we accepted it in the bigger picture of much improved insulation of the other 90% or more of the perimeter and slab.

 

For us, the trade off of extra cost and effort of disrupting existing stairs wasn't worth it. Whether you're living in the property at the time will be another factor.

[haythorn_1]

Thanks all. Interesting as I thought the resounding view would be to remove it.

 

i think I will wait to see how easy it is to excavate below. Ours is a u-shaped staircase with 3 flights (if that makes sense). It has 4 posts which I pretty sure are supporting it on the ground.

[NandM]

I have a similar conundrum and will most likely do as @torre....although I'm also contemplating on removing the final two steps and 90 turn to have the staircase face a different direction.