Floor options on top of concrete base

[DirkG]

In the middle of an extension and was all set for the final screed (approx 75mm) to go onto the concrete base but we're having second thoughts

Mainly started having doubts due to the plumbing work (plastic pipes + push fit connectors) which hasn't been pressure tested, but also how well it's going to bridge/meet up with the rest of the house which is floorboards (starting to lose faith in the builders doing the right thing!)

So is there the option to batten + floorboard over the concrete base?

I believe there may be building regs issues due to ventilation which seems to call for 150mm gap beneath timber floor?

 

[DirkG]

This is where the old floorboards will meet the new screed

 

[geraldthehamster]

Personally I wouldn't put push-fit connectors in a screed. Continuous plastic pipe is OK. Copper pipe isn't, unless protected. Does your screed thickness allow for the finished floor covering, so all will be level with the adjacent boards?

 

[Doggit]

Have they laid the concrete, and is there insulation underneath; and what you're floor covering going to be. You shouldn't need a 150 at gap under there as the floor shouldn't be damp. If you're going to continue the floorboards into the extension, then you could look to glue and screw some battens to the fllor(depending on the depth of the DPM under the concrete) and then screw the floorboard to that; or you change the push fit pipes for glued ones, and then get the plumber to test everything before you lay the screed.

In terms of copper pipe, there will be a bit of a corrosion from the cement, but then the reaction will stop, so it's more a case of insulation needed round them rather than protection - depending on what they're being used or of course.

 

[geraldthehamster]

In terms of copper pipe, there will be a bit of a corrosion from the cement, but then the reaction will stop, so it's more a case of insulation needed round them rather than protection - depending on what they're being used or of course.

Are you sure? I'm certain I read a story on here of someone whose copper pipes had corroded away to nothing in a concrete floor...

 

[Doggit]

It's an urban myth; once the concretes gone off, so does any further corrosion, and it's very minimal to start with, but you can get issues with nitrates etc causing stress fractures in the copper, so it's good to warp it, but even better to insulate it as well.

 

[geraldthehamster]

I guess there's also the contraction, expansion and movement issue. I buried plastic heating pipe in a concrete screed but I ran it through plastic waste pipe.

 

[Doggit]

Neat trick; nice lateral thinking there Gerald - but I'd still have insulated it first. There's a lovely warm concrete floor going into the living room here, but the rad doesn't get that hot.

 

[geraldthehamster]

Another trick - to avoid standing on the pipe while laying the screed, fix strips of Celotex where the pipes will go, lay the screed to that, remove Celotex later and install pipework, filling over the top.

 

[DirkG]

Hi guys thanks for the comments - totally agree about not putting the push fit bits into the screed, that is what got me thinking if there were alternatives

What I've done is boxed in all the plumbing joints so there will be access after the screed goes down, and run the pipes in conduit (the black stuff in the picture)

I'll check with B Regs but sounds encouraging that I might be able to batten+board. The concrete base/oversite is made up of hardcore, DPM, insulation and concrete, with approx 75mm left to be made up by the screed

 

[DirkG]

Ok have checked with Building Control and they have said I can do whatever I want as the current base already has the insulation etc.

 

[Doggit]

As long as the joints have been glued, then there's no need for access to them. But if you screed, then you need to be damned careful to get your heights just right, otherwise you'll end up with a lip/slope on the join. I you screed to the current floor level, then you can go straight across from there.

 

[DirkG]

Doggit - that's one of my concerns, how nicely they can meet a timber floor with a screed with matching levels etc

 

[Doggit]

They can screed to the top of the floorboards without any problem, and they should be able to "juggle" the battens to get the heights right, but it won't be so easy. It'll all depend on what you want for your top covering as to the best way to decide on the next stage, and how good they are at laying a level screed. The last caveat, is that if you have a thin final layer, then you'd notice the difference going from the wood to the screed.

 

[DirkG]

We're looking at luxury vinyl planks - installation to include over-boarding the existing floorboards with ply to make them level and bring up the concrete floor with a levelling screed (more screeds!)