Awww. Cute pooch. Great job you've made of that, especially while living there.
I'd compromise on insulation for solidity, it will give a high point load so could crack the screed. You could have 4 people climbing the stairs behind each other, all their weight in one spot. Stand it on solid (not frogged) concrete bricks mortared in on the concrete.
The concrete won't be very cold there anyway, as it's pretty much in the centre of the building. You could put an upstand of insulation around it, but I wouldn't worry. Just keep the UFH pipes a little distance away.
But perhaps I'm over-worrying. I'm going to bet that housebuilders don't care, but they're more about profit than quality.
Thanks Ivor Windybottom! It actually wasn't anywhere near as disruptive as I thought it would be (for anyone reading in the future, I'll put the steps I took at the bottom of this post, it is mostly various different ways of supporting the stairs to do various jobs).
And thanks for validating that option 1 is the way to go. I think it's a fair trade off to spend a few extra pennies on heating to have a proper solid staircase. I have an old lintel in the garden, I'll see if I can cut that up to use as a support, otherwise bricks will do the job.
It's always bewildered me that stairs are often just plonked on floorboards with no support underneath, their contact patch is so small!
To future readers - steps for replacing timber floor with solid floor (2 of us started on Monday morning, and concrete came at 2pm Tuesday).
- Rip up existing flooring and floorboards
- Build temporary supports for stairs out of bricks to support existing joist(s)/floorboards that the stairs are sat on.
- Remove all joists and sleeper walls.
- Spread out any dusty/sandy stuff that has collected under the floor, wet with a hose, and compact with wacker plate (watering my hall floor was a weird experience).
- Support the stair case so you can remove the joists/floorboards underneath it. I did this by building wooden frames resting on the floor, and screwed in to the newel post & stringer. They looked a bit like mini goal posts.
- Support the stairs again! I did this with bricks directly under the newel post and stringer to take up as little floor space as possible. I then removed my goalposts. Steel packers that the window fitters left here were very useful for this, but slate is also good for filling small gaps.
- Put in 200mm MOT type 1 in three layers, each layer dampened with a bit of water and wacker plated.
- Damp sand blinding (10mm) tamped down.
- I built yet another support for the stairs, as shown in my original photo. I had a big bit of timber from another project, and supported it on bricks on top of the MOT at each side of the room. This made it easier to lay the DPM and concrete. Remove the old supports.
- Stick down a DPM
- 1 cubic meter (120mm deep) of concrete chuted straight through the front door, and the manic hour of spreading it around and tamping it to some kind of level. This was my first attempt at a concrete slab, and it turned out well I think, with only 8mm deviation across the slab.
- Build a bunch or bridges out of some old chipboard I had lying round and the floor joists I took out to allow us to walk around whilst the concrete dries.
Next up:
- Support the stairs and wait 30 days for concrete to dry (going to lay a temporary chipboard floor).
- I'll probably use some sand I have left round to level the floor better and stop insulation rocking
- 150mm PIR insulation
- DPM
- UFH pipes
- Liquid screed - wait another month or so for it to dry
- Final floor finish
I've done all the above "Next up" steps in other parts of the house before, so they should be less stressful than the past few days!
