Hesitant to screed floor of Victoria house prior to flooring being laid

[WashableWool]

We want to lay some flooring in our lounge, it’s Victorian but the floor seems pretty level. Currently there is LVT in there laid by the previous owners but we’re thinking about engineered wood, possibly in a herringbone pattern.

We’ve been told that the floor will need to be screeded. I’m a little hesitant about putting a layer of concrete all over the floor given the house needs to breathe.

Are my worries unfounded?

Is the current floor a solid one?

You really want @pigletjohn here, but I'd be thinking the same as you.

Assuming you've established that it is floorboards over a void rather than a solid base (which would answer the breathing question). There is probably a workable alternative in using a strong but flexible underlay, or plywood expertly laid so it doesn't have even tiny lips between the sheets.

For tiles which cross to flooring types I've used ditramat successfully and I've used engineered wood across an area of old concrete screed merged with new underfloor heated screed, that's my only experience.

Currently it’s floorboards, the green underlay, and then what looks like LVT click tiles.

The room is above a cellar room which is a touch damp but does also have a radiator down there so it’s ok for storage.

I've no idea why anyone would want to put screed down.
Check the cellar has adequate ventilation. Remove click tiles, check condition of original boards and over lay engineered boards

Apparently it's because to lay the herringbone engineered wood, the floor has to be absolutely level, with very little tolerance. I understand that, but I feel there must be another way other than concrete screed? What if in the future we need access to lay pipes or something?

Also surely the floor must have been made good by previous owners in order to install the LVT click tiles?

[Hmm]

If it's a boarded wooden floor, it will move a bit, so if the supplier says its necessary, I'd strip off the old covering, repair the damaged and missing boards, screw down the loose ones, and overboard with ply. Don't screed.

The ply will leave the factory in perfect rectangles that will fit together, so you put the whole boards in the middle and along traffic routes and doorways, and any cut pieces go round the edges.

It would be a good idea to clean out the void, unblock the airbricks, search for any signs of damp before reflooring. If you think you might want to insulate the floor, put mineral wool rolls between the joists. There will never be a better time. Do any underfloor wiring and plumbing, and insulate the pipes.

You can make a hatch into the void for future access. Put it in a corner where it will not get walked over.

Hi @PigletJohn thanks for the tips. You make a good point on the piping - we have a cold water pipe that runs outside and burst last winter. It needs to be run inside, either next to or potentially under the lounge floor so I have contacted our chap this morning to ask when he can do it. So thank you for that. It’s one of those jobs that needed doing!

May I ask why you say not to screed?

Thin concrete is liable to crack. The wooden subfloor is not especially rigid, it will expand and contract with the weather, and will have a little flex.

It will also be a pig to get through if you ever need to take the floor up.

Using a flexible wood floor adhesive would allow for inconsistencies in the existing floor

When you say wooden subfloor, do you mean the original floorboards on top of the joists?

Yes this house absolutely moves with the seasons, we have noticed this even in the short time we’ve been here.

I am confused as to why the fitter was so adamant that it would need screeding - because surely all Victorian houses move like this and yet I’ve seen plenty of houses with the herringbone engineered wood, surely they haven’t all been concreted underneath!

Maybe look for another fitter.

Our neighbours have this type of floor although it's solid wood or engineered not lvt and they call it a floating floor

Yes, ours will be engineered wood. Thank you I will look into a floating floor.

And yes @PigletJohn we shall definitely get some more quotes in. It’s a shame as the one we called was recommended to us by the flooring company; they gave us his number and said they’ve been using him for 25 years. For him to be so adamant that the floor would need a concrete screed when he hadn’t been to visit or see the house just put me off him!

We’ve had herringbone engineered wood laid throughout downstairs of our house. The solid floors had to be screeded and then the wood floors needed different thicknesses of ply to bring it all to one level. Herringbone needs a very even surface, it cost a fortune but the carpenter that did the prep work was absolutely spot on and the result is incredible.

I'm glad you have asked this question. We plan an extension and I have always wondered what happens with the old existing sub floor if we wanted the same flooring throughout the old and new.

Good to know that ply is a possibility. We have taken the flooring back to the original boards now and I have to say I think they’re pretty level to me, certainly there is no sagging/gaps underneath the skirting boards which seems like it must be a good sign after 130 years? 😁

I have contacted more fitters on @PigletJohn’s advice so I will report back what they say!

My flooring people recommended a plywood base. All went well, the flooring went down perfectly, and there's been no movement. That was about three or four years ago.

Great to know.

Sadly I’m starting to think that perhaps this floor fitter is ‘in cahoots’ with the flooring retailer. His installation price per m2 sounded good but maybe that’s low because he then adds on a mandatory screed!

So the new floor installer said the floor is in good nick and doesn't need a screed, just a ply base. He said he will glue the joints of the engineered wood and use secret nailing. Hopefully this sounds okay @PigletJohn?! (Thank you for all your advice!)

Oh and there would be an underlay too, of course.

We're putting solid herringbone parquet blocks down, mostly on floorboards, one section on concrete. Even on the concrete floor the sellers of the blocks recommended us to use ply as a base to get it really level and flat. I'd have thought engineered wood would be no different.
Our old house we had blocks on concrete, stuck down with bitumen, but that's a bit old-school and had been down about 60 years.

What you have described is normal building practice.

In over 30 years in building I have never
heard of anyone putting a screed over a wooden suspended floor

Sorry I meant to add glue and secret nailing might be considered slightly belt and braces but will certainly do the job.

The last herringbone timber floor I laid was with normal wood glue on the joins and thicker flexible 'tile adhesive type' wood glue to fix to the sub floor.

Its the first time I hadn't secret nailed and I was slightly nervous but it was what the manufacturer recommended and still looks fantastic 5 years later.

I've used glue instead of secret nailing or traditional cut nails on many parallel board floors since and find you get no issues of squeaky floors subjected to flex like you can with nails

We had planned to renovate the floor boards in our house but they weren’t in good enough condition and we didn’t have the £££ for wood as it wasn’t part of our budget or plan, so had lvt herringbone fitted. One fitter told us to screed and we had the same worries as you so went with another guy who did as Piglet John suggested.

There was evidence of old wood worm in ours which the builder was pretty sure had been dealt with, but as everything was pulled up anyway, he treated the joists etc for woodworm just in case, cleared cavities, used some sort of insulation that can breathe, then floorboards back down and made good, then ply then some sort of foil underlay, then the lvt, it is perfectly smooth and flat.

Do you think there might be an issue with the secret nailing piercing the top of the underlay @Surplus2requirements? It’s a damp proof one with a sort of foil on top but I was worried the nails would pierce this, could it cause a problem?

Would you ever do underlay underneath the ply or is that just wrong?

Thank you for your comments, very reassuring!