Concrete floor pouring advice

[Mr Punter]

21 minutes ago, saveasteading said:

BUT seriously consider postponing this and getting a professional gang to do it.  

+1

 

Because you have a series of small rooms, this job looks difficult.  Get several quotes for someone skilled and experienced to do the job.

[Nickfromwales]

I’ve been at this for > 30 years, and my ass still goes through various differing diameters whilst the wagons are backing up; at that time the opportunity to check / change anything has completely evaporated.

 

 

[Coll659]

Thank you so for the responses. Definetley confirming my thoughts on how difficult it will be. I'm working my way through all the points one by one so will likely be back back with me questions. We have a couple more semi experienced people on board and are in the process of trying to get a professional or two to come as well. And just planning everything to the tiniest detail. I've lost many hours sleep to this recently and really appreciate the advice. We have some phone calls to make next week and see what we can figure out

[Mike]

I wouldn't attempt to do what you're planning either. If the rooms were larger I'd probably spread it over 3 days and, instead of pumping it, I'd shoot it in through the windows and have at least 2 people with muscles to barrow it into place. However as the rooms are smaller I'd probably bring in the materials and mix it on site.

 

On 11/09/2025 at 12:28, Coll659 said:

How do I make joints between the rooms taking into account there will be underfloor heating pipes going through doorways. Should the slabs be completely separate for each room to avoid cracking and allow expansion?

I'd have formwork in the doorways and create expansion joints. Either way, shroud the UFCH pipes with lengths of flexible conduit for 250mm or so either side of the junction, so that any movement is isolated from the pipes; if you've missed them out you can slit them lengthwise and clip them over the pipes, then tape up the slit.

 

 

[Nickfromwales]

54 minutes ago, Mike said:

I'd probably bring in the materials and mix it on site.

Ouch!

 

Ready mix all day long, even if barrowed in.

[Onoff]

How about having a go at doing just one room on your own to start with, bulk bags, hire a cement mixer etc with a few mates to help. You'll either think "that was manageable" and have the impetus to crack on or "that was bloody hard work, I'll get the professionals in". 

 

Take on board the above tips like vertical battens for level. I would think you'll need a stronger threshold board at the doors if doing just one room as in to resist the side pressure. 

 

Tbh when I do my next rooms here, one at a time I'll be screwing screed rails to the walls like last time. It worked so well for me I'd do it again. 

[Spinny]

47 minutes ago, Onoff said:

I would think you'll need a stronger threshold board at the doors if doing just one room as in to resist the side pressure. 

Yes. Our builder decided to tack mortar the course of blocks running under our bifold opening - on the basis it would make it easy to remove them to machine cut to threshold height later. Turned out months later we discovered those blocks had bowed out into an arc under the weight of the concrete pour - leading to much delay and remediation work. (TBH It was a larger open slab - about 40 sqm - and a 3.5m opening).

 

How deep is that concrete going to be ?

[saveasteading]

An alternative.

Use a screed mix, which is sharp sand and cement, low water content and probably fibres.   You can barrow it for a few hours , while tamping it in place.

I'd still recommend using professionals...but the pressures are much reduced.

This also depends on the design as it isn't structural concrete, but fine for most domestic  situations.

 

[Iceverge]

On 11/09/2025 at 16:20, Coll659 said:

have no experience but are useful for lugging around hoses where we need them

 

When it comes to concrete work and newbies they will be of limited use, (myself included when I first did it).

 

I've seen the pattern too many times. 

 

They'll appear full of enthusiasm, gloved and booted up. The first 5 minutes will be all action but they'll quickly tire, start leaning on rakes and wondering "is there a better way to do this" because they can't fathom how much suffering it is.  They'll start job switching and going off on side projects "I'll just start over here in this room" forgetting they're making a mess for later. 

 

They won't have the "touch" required with concrete. When raking in front of a screed they'll be constantly banging it, or taking huge lumps and making holes or dragging the surface so it's like a rice Krispy cake. 

 

They won't be used to the time pressure and heavy work and will respond to the robust direction of the gaffer by sulking. When given a lighter support task like washing up (very important) they'll see it as punishment for being sent away from the main action. 

 

What you require is someone who has spent some time in the military, is a strength endurance athlete and is also a plasterer. 

 

 

 

[Onoff]

I did my 3 x 3m bathroom on my own, mixed in a mixer and levelled with the screed rails, no problems. 

[Onoff]

Have a look at @oranjeboom's thread as to how it can go wrong, the UFH pipes can lift and poke up out of the concrete. And he got someone in!

[Coll659]

We are meeting with a professional concrete guy tomorrow so to discuss the job. With a bit of luck we can convince him to take the job on and do it for a reasonable price but we're not sure yet. But at least we will get more info and advice and perhaps some local contacts. 

 

A screed mix might be worth considering.

 

Yeah I read through orangebooms experience so I'll definitely be vigilant about that! My underfloor heating will be stapled to the insulation which should hopefully avoid the issue of the pipes and I'll be vigilant about making sure the rebar stays down.

 

Thanks again for everyone's advice, I'm certainly taking it all in and will let you know what we get after meeting with the professional tomorrow

[Iceverge]

An option you could explore to save a few £ is to pour every floor to say 25mm short of final level with concrete and tamp it to get it fairly flat. 

 

Then get a pumped screed to make the final bit perfect.

[Nickfromwales]

2 minutes ago, Iceverge said:

An option you could explore to save a few £ is to pour every floor to say 25mm short of final level with concrete and tamp it to get it fairly flat. 

 

Then get a pumped screed to make the final bit perfect.

Too much money on double-pumping then? Plus no screed companies want to pour less than 50mm unless it's had a very expensive primer applied beforehand.

[Iceverge]

2 hours ago, Nickfromwales said:

Too much money on double-pumping then? Plus no screed companies want to pour less than 50mm unless it's had a very expensive primer applied beforehand.

 

Good to know about the 50mm. 

 

I'm toying in my mind with methods to avoid the human suffering if concrete pours. 

[Nickfromwales]

53 minutes ago, Iceverge said:

 

Good to know about the 50mm. 

 

I'm toying in my mind with methods to avoid the human suffering if concrete pours. 

Ask me and the good folks here. 
 

We speak from experience, which is gold dust  

 

  

[Coll659]

After the advice of pretty much everyone, for once I am going to admit defeat and have some professionals in for this job. We  have found a couple of options we are happy with and will readjust the budget a little to accommodate but its not something we can afford to go wrong. 

 

I will take some pictures and update you in a couple of weeks when it's done but thank you so for your advice and help and I now know what to watch for when it's poured and what to prepare 

[saveasteading]

22 minutes ago, Coll659 said:

admit defeat

A tactical withdrawal is preferable to suffering a massacre. Well done General.

[Andehh]

Sounds like the right decision, what sort of quote for what sort of work out of curiosity? 

[Coll659]

We have a quote of approx 2700 EUR. That's 100mm concrete throughout the house (approx 110m2) with Labour. That's in central Slovakia. 

[Coll659]

Things are progressing and we have some professionals lined up for the concrete (professionals doing a side job for a friend with me and our mutual friend helping). Quick question on the rebar chairs. I have one room almost ready but found the rebar might be an issue. It's 4mm composite on 50mm chairs. However the chairs I got will just pierce the foil and insulation if you step on or close to them. Stepping between is fine as the composite rebar is very flexible so just bends but this might be an issue when they are laying the concrete. It's not easy stuff to walk on. Do you think the rebar chairs with the wide circular buttons would fix the issue or does someone have any tricks for this. 

 

Also my concrete guy is quite worried about the the rebar floating but I think tie wrapping it to the chairs and then to the underfloor heating pipes will be fine? 

 

Floor build up is: 

Sand blind

30mm EPS

Dpm

Insulation (200mm EPS in part of the house, 100mm PIR in the rest) 

Under floor heating foil

100mm concrete

 

(And round the edges 30mm EPS and foam expansion skirt between Dpm and underfloor heating foil)

[Nickfromwales]

Connecting things to the pipes is fine, but I’d fit a lot more staples, and make sure the pipes are full of water so they don’t have any buoyancy (and don’t want to float).

[Coll659]

Thanks I'll add a load more staples. And yeah I plan to pressurise them all up to 4 bar (our mains water pressure) to check for leaks before and to monitor during laying

[Mike]

On 20/09/2025 at 21:15, Coll659 said:

Do you think the rebar chairs with the wide circular buttons would fix the issue or does someone have any tricks for this

Yes, that will help; I used to use wide-based concrete ones.

 

However personally I'd likely skip the reinforcement. That's not something I'd have suggested until recently, but the need to add D49-style* reinforcement or reinforcing fibers, which was previously mandatory in France, was dropped from their Building Regulations in 2015 following an investigation what which concluded that neither served a useful purpose. Consequently it's something I've omitted on my current French project.

 

*In fact the French used to use a lighter fabric than D49.

[Coll659]

It's done!!

 

Just wanted to say a big thank you to everyone with the advice on this one. 

After the advice I changed plans and in the end got a sand cement screed laid by a professional company who did an amazing job and finish. 

 

Time to move on to the next stage (I'm sure I will gleaming you wisdom again) 

 

Thanks again, few pictures before