Floor height worry: underfloor heating

[ShortLass]

My home refurb project includes underfloor heating for the ground floor. This would be an overlay / low profile system such as Polypipe with 18mm boards laid on top of the concrete floor. Engineered wood flooring on top. With underlay, this raises the floor level by up to 30mm (all the above elements minus existing tiles which are coming up).

Not hugely significant until we get to the stairs in the hallway. Because the floor level is raised, the bottom step is shallower than the rest. This is against building regs.

Architect suggested "scabbling" (sort of sanding down) the concrete floor to achieve the right floor level. I am anxious about this because of the cost and of reducing the concrete which was presumably put down at that depth for a reason.

Second suggestion is to replace the staircase with one where all the steps are even, including the bottom step. Sounds drastic.

I said maybe just forget it and have radiators. Except everything was designed around underfloor heating and it's soul destroying to redesign at this late stage.

One thought I had was just having ufh in the open plan lounge and having a threshold at the door down the 18mm to hallway level. That's a big change in levels between floors and I think it would look and feel bad.

Alternatively, have the threshold from the door to the lounge slope down the hallway until it reaches the part at the front where the steps are. Would be, maybe, a 2.5 length of hall which would need to slope. (Not sure how a builder would achieve that easily). Bit of a bodge?

We looked at incorporating the buttom step into a raised platform, but it stops the front door opning properly (and wouldlook odd IMO).

I don't know what the hell to do about this. The architect only just mentioned it before the final drawings were done. Before that I knew nothing about the building regs with regard to stairs. The issue only came up when I said that she made an error in stating electric ufh instead of low profile wet (water pipes). She had just assumed I was having electric. But electric is too expensive to run (says everyone who's had it) and is only an additional hest source; I would also need a fire or something if I had that.

Of everything I have posted, this is the most important. Looking for any experiences of reducing levels of concrete floors (scabbling) or any of the above.

So what's the total floor build up of the underfloor heating?

You could do:
Underlay 3mm
Pipe in screed 25 mm (with special lattice and screed)
So that's 28 mm plus the engineered wood.

So what's the total floor build up of the underfloor heating?

Overlay pipes: 18mm
Underlay: 3mm (although 5mm would be better, but 3 will do)
Engineered wood: 14mm
Less tiles which will be removed: -7mm (ish)

TOTAL: 28mm

I spoke to building control about it and raising the floor at the bottom of the stairs like this will, indeed, break building regs. So I can't do it. I need a solution.

Pipes in screed isn't generally used for retrofit as screed needs to be something like 50mm min if has fibre mixed in. Hence these specially designed overlay systems. Thanks for the suggestion, but even 28mm plus engineered wood is 42mm, even higher.

That top item is overlay board plus pipes: 18mm

Is the staircase pretty standard in construction and carpeted?
If so, you can divide the discrepancy over all the steps by padding each step to a different height.
I.e. 28mm over 14 steps
It's one 26mm second 24mm and so on (you need a joiner who is good at maths)
Simplistic example but it can work.

staircases are much cheaper than you think.

What are its dimensions? How fancy is it?

Bog standard staircase, PJ

I had a wee look at staircases and so I see that they're not that expensive. It's the labour cost of ripping one out and putting a new one in that is a bit of an unknown. Plus, y'know, replacing a perfectly good (if bog standard) staircase. Although I was planning to replace the spindles and handrail with oak to look nicer if budget allows.

Replace staircase safest option?

Yes, replace

It sounds like you've checked, but I don't understand why your existing staircase has to comply with this aspect of current building regs just because you're raising the ground floor level next to it. You're not doing any work to the stairs. The rise isn't even changing, you would have this issue if you put a thick underlay with shagpile carpet next to it! It doesn't make sense to me and I would look into it further, if it was me.

I know what you mean, HiDBandSIL. I was like, really? I rang the technical support people at the UFH place and they hadn't heard of this being an issue before. People just put it down. Probably without building regs signing off.

After my architect told me of these stair regs, I did a google. She's right, every stair must be same height.

I rang building control at local council. They said a shallower bottom step is not an issue stepping up to it, it's stepping down that's the issue. People instinctively expect to step down an equal amount each time and when the last step is different, they can falter and fall. I totally understood what he was talking about.

Didn't seem to be any point trying to find wiggle room after that. Even if I decide that falling on the step was a risk I would be prepared to take, I am having to have building control sign off on the extension and if they looked at the floor and told me I have to take it up, that could be a costly mistake.

I wonder what would happen if I simply decided to get rid of the floor tiles and replace with a nice wood floor. Or a thick carpet. Or put a mat at the bottom of the stairs (it's next to the front door, so I could have a large shoe-wiping mat in theory). All those things would raise the floor level a bit.

Can you not leave the floor tiles for now, have the uf heating put in the rest, get it signed off and then lay the new flooring into the hall so the levels are eventually the same?

Think of the amount of people that must update flooring and alter the height difference by a few cm..... I'm sure no one would even think to check with BC...

I would replace the staircase and keep the UFH - it's a much nicer heat

Bog standard staircase is not that much - do you have a joiner working for you elsewhere on the project ie fitting the flooring...would he do the staircase too?

spydie: Don't think I have to nerve. Plus, suspect building regs guy has a point.

Chis&Fips: It's looking that way. I'm still to get a builder on board (they wanted architect drawings first), but I'm sure there will be someone of that ilk on the team. You know, I love the thought of UFH. Really want it upstairs too, but people who don't frequent MN/Talk/property think I'm mad.

Thanks everyone for helping me through this latest crisis. Have some virtual , as pixels are non-fattening.

We found that about people too Shortlass...even our plumber was sceptical at first (ours was his first retro-fit installation) but once it was up and running his hoodie came off pretty quick and he was sold!

I don't get why, you effectively get a floor sized radiator - heat rises so job done

Hope you get sorted

I appreciate this suggestion is probably too late but would the following not have worked.
On the assumption that you are installing wet underfloor heating upstairs as well and that the change in floor height is 30mm.
The bottom riser will be 30mm too low and the top riser 30mm too high. If you increase the thickness of each step by 30mm then all the risers will be the same and the original height. Just shape the new step to fit the old step and create a new nose. Or you could go one step further and also fit new risers. You still have the strength of the original stairs just have to cut new high density board to glue/screw onto existing stairs. No upheaval, no making good and a simple process.