french floor

[BillH]

Hi,

foolishly we bought a house in fance. Many chartersitics of this hourse you will all be used to..

we have a single large area of about 75 sq m we need to lay a screed. .

earth, compacted rubble and a liner, cement reinforced screed of 6cm .

On top we are going to put a good quality laminated floor product. I chickened out of a real oak suspended floor .


The walls are stone ,, They don't know lime plaster at all , and therefore I assume they dont know about lime screeds .

The internal walls are currently plaster, but will be re covered with plasterboard insulation.. ( I really did resist but gave up , resistance was futile ! )


I am worried that any of the damp rising from the earth , hitting the membrane , going to the outer edges and then using the walls as a wick ..


Any ideas ? or will the compacted rubble tacke care of any possible damp.


thanks..

 

[88v8]

Hello and welcome.
House in France... bliss... potentially, or a pile of merde.

Unless the house is perched on a dry mound, yes any damp will hit the liner and go into the walls. Not instantly, but inexorably. The under-rubble will not prevent it.
What is the present floor? Are the walls built and pointed in lime?
One has to respect the original structure, which usually means something like an earth or cinder or - nowadays - limecrete floor, with stone or quarry tiles bedded and pointed in lime. Laminate flooring is not suitable as it needs a dry screed.
The walls should be lime plastered, not insulation board, that will just hide problems, and then only for a while.
Finding a builder is not just a French challenge. Most builders in the UK don't 'get' lime. Their default involves cement and gypsum plaster and dpms. Do you have a UK builder you trust? You could give him a 'holiday' and take him over there to do the work.
You would also need to source the materials of course. It may be that Ty Mawr will be able to advise you on lime suppliers in France, and they in turn may be able to point you towards local builders with the right Period instincts. This would be a better solution, as importing a builder would not endear you to the locals. I presume you have fluent French...

We always like pictures...

Ivor

 

[Penners]

Welcome to the forum, BillH.

Whereabouts in France is your house? It's my (limited) experience that in southern France they don't really bother much about damp-proof courses in walls or floors, because there's so little damp in the ground. It's also my experience that they are, in fact, much more used to lime mortars, screeds and washes than we are.

But builders :roll: ... the average Provencal builder seems to make our British ilk look like paragons of promptness and reliability!

As 88v8 has already said, I'm afraid there is no way of avoiding the risk (but not certainty) that an underfloor membrane could cause subsoil damp (where it exists) to migrate sideways into the walls. The normal solution to this in a new-build is to insert a DPC into the wall that is contiguous with the underfloor membrane - but I assume you don't have this option.

Why did you 'chicken out' of a suspended floor? Given your recognition of the risks involved in a concrete screed, I would have thought that a suspended floor above unscreeded soil would be best way to proceed. And the saving in the cost of concrete, etc. should go a decent way towards paying for the timber floor.

 

[Flyfisher]

Photos would help to show what you're dealing with.

My immediate question is why do you "need to lay a screed"?

We have some rooms with a suspended floor over bare earth and the floorboards are completely solid and sound - and I don't even think they are oak.

It seems to me that laying a concrete slab as described is not in keeping with the property and carries a number of risks (that you've already identified) for which a remedy could be very invasive to the existing structure (and might not even be particularly successful).

From the information at hand, I don't understand why anyone would want to risk all that for the sake of some laminate flooring when a well-ventilated suspended oak floor would do a perfect job and be essentially risk-free regarding possible complications.

And all that is before even considering the beauty of a solid oak floor.

 

[citizensmith]

We have a house in Brittany with similar issues. The floor in the livingroom is french concrete with a wierd broken leather pattern embossed in it. The floor slopes considerably across the livingroom dropping 6 inches over 20 feet. My kids use it to ride armchairs on castors across the room!

My planned solution is to suspend a level floor over it using pine T&G. I will leave the floor beneath as it is.

Reason 1: It probably is "breathing". its poor quality thin concrete and there is of course no DPM below.
Reason 2: Once in extraordinary heavy rain a small stream formed coming through the stone back wall, crossing the room and going out of the door. Aha! thats why there's a slope!

So if it happens again it can quietly pass under the floor and out.

As for walls, my inlaws stripped most walls back to bare stone. The y were simply plastrered in mud from the garden with some bits of straw/grass and then limewashed over. I wouold like to replaster all the walls in Lime if and when i get the time and can sus out how to do it.

Please dont throw up platerboard and concrrete render everywhere like my father-in law did, I am now slowly taking it all down!

 

[Keith Bowman]

Our experience with Provencal builders is the same - we are still waiting for a quote from one after ten years. (And he hasn't forgotten - he even mentioned doing something about it when we met him in the street last year!) They are also like British builders in that most prefer to use plasterboard and cement...but there are specialists who know about older houses, breathability, lime, hemp insulation etc. And a great deal of the lime used in Britain comes from St Astier in France anyway. It is quite possible they could put you on to suitable craftsmen:-
Dordognaise (C.E.S.A. Group)
24110 St Astier, France
Tel: 05 33 54 1125
Fax: 05 33 04 6791

 

[Moo]

Pay attention to the wise words of Penners, Bill. He knows what he's talking about.

I was on the horns of a similar dilemma recently, but I'm following his advice and going for a suspended floor (which has the added advantage that we can do it all ourselves and put the money saved towards better quality boards).

 

[BillH]

o my good ness where do I start.. ?

The property is in Lower Normandy/close to calvados broder ,


Huge pressure to insulate, from everybody who came into the house, even if they were not involved with the building side.

Likewise to lay a concrete screed , it was clear some other people in the village had problems with floors they had laid warping, and I just didnt want to go there , so I made a when in Rome decision for the screed, not yet laid. However, due to be going in in two weeks.

My huge question mark has arisen because whereas I thought the project manager knew his stuff, I am now pretty sure he hasn't got a clue, and is relying on the suppliers to deliver a good job. However he doesn't know what a good job is or isn't..so I am signed up for a couple of things.. and getting worried.
I laid out the problem about the screed, thinking there would be a french way of dealing with it. No comment other than come and supervise yourself, (or words to that effect but not so blunt ) and then of course the problem is down to me. So I am looking for a solution .


I am getting the impression this will turn into a "bodge it and bunk" operation. I was at first taking comfort from the automatic 10 year guarantees that come with all french work.. not sure.. not sure.. !!!! put this to one side, still looking for my solution. However what you guys are saying is , I am buying trouble putting in the screed ... does that mean its impossible to put one in ?


Taking brits there is not easy or straightforward, although I have costed a couple of the jobs using Brits, again , avoided it for the moment, logistics etc permissions and and and/ ..


Bill

picture attached, floor will be about 24 inches from the ground level

 

[tobydog]

Hi BillH,

The ten year insurance you are referring to is aptly called Decennial Liability. It is a compulsory insurance in France but it has its limitations. I don't believe, for example, that if a contractor laid your floor, and you subsequently found minor damp appearing, that the insurance would respond. It's primarily designed for cases where certain premises become uninhabitable. You might find the following helpful:

http://www.ffsa.fr/sites/jcms/c_51299/how-decennial-liability-insurance-works?cc=fp_7202

 

[JoceAndChris]

Really too late to wriggle out of the concrete screed BillH? I'd also be pushing for a nice wooden floor over earth, we have these here and they're great. I don't have carpet, the breezes blow through, the house is draughty but dry.

My (limited) experience suggests your plan is likely to cause some damp. Where there's concrete/cement in an old property, damp typically moves round it to where it can, and sits there, if it can't escape.

We have a concrete floor in our partially sunk kitchen and it's caused damp to migrate into the bottom of the walls. We deal with this with very good ventilation and a dehumidifier, and don't really notice the damp - but were we to cease the heating/ ventilation/ dehumidifying, I'm quite sure it would revert to the mouldy condition it was in when we bought it. Partially sunk of course makes it much worse, but I'd still try to get out of the decision you've made if at all possible. I do sympathise with the pressure, particularly as you've already engaged the builders.

 

[Penners]

thinking there would be a french way of dealing with it.

Indeed there will. It will involve a shrug of the shoulders, a spreading of the hands, a puffing of the cheeks and the word "Bof!".

 

[Moo]

it was clear some other people in the village had problems with floors they had laid warping

Ah, but how high up from the ground were these floors?
And - had they provided proper under-floor ventilation?

 

[BillH]

Thankyou everyone.. Penners you got it in one !

So let's say I change the screed, not being a builder, I'm looking to get a fair specification to work to. can you help ?

take out some of the earth and also compacted rubble at far end.

create piers in concrete ( renegotiate screed to this ) across the short side, 7 m >
leave a gap between the pier and the wall say three inches ?

How frequently /how many concrete piers along the long side of 11 m ? ( ie stretching across 7m in length )

I assume I will put 4 inch joists along the piers,

damp course lining between the piers and the 4 inch 7m joists

and then 3 or 4 inch joists on top of those joists to take the final floor along the 11m aiming to be about one inch below the desired hieght of the floor, to allow for flooring.. I assume flooring is 1inch or so.(& will check this out ) .

How far apart should the second layer of joists be ?



is that about it ?

insulation of any sort ?? this is not a draughtly listed building, I have one of those here in the UK !!! so aiming for a bit of comfort as well !!! Or do they not go hand in hand ?


second question, if I cant change the screed, is it enough to leave a one inch gap around the whole floor.. ?
so it doesn't touch the wall.. ? or is that unlikely to work..

thankyou for any input..


rgds
Bill

ps I suspect the other people in the village didn't have a huge gap between earth and floor, but I really don't know.. I was aiming for about 24 inches , is that enough ? if I can change the specification that is..

 

[BillH]

I just spoke with an English guy in France who supplies flooring to the UK and lays in france..

He also talks about screed and a small gap of an inch or two tween the screed and the floor.. It seems to me there is just one mind set there !

Although he acknowledges the potential risk of damp heading for the the walls, its the way he has done it for twenty years .

Have tried a french drain on one side of the building, needs to be done again as the pipe was laid at about 4 inches in depth..


I intend to go tongue and groove , unless there is some horrible reason for not doing so.. Thus reducing the airflow into the room ! Please comment

understand I should leave an expansion gap for the floor to expand and contract. ...

rgds Bill

 

[BillH]

starts to look like this..

two choices. Ditching laminated floor anyway . Opting for T&G floor boards

screed, with a 6 inch edging in polystyrene around the whole floor, between floor and the walls in attempt to create a gap between the screed and the wall. Liner brought up from the base on all four sides of the screed.

Depth in the screed to allow for a wooden floor negotiable, floor supplier is suggesting just 22mm battons plus floor board thickness of 22mm total 44mm depths .

The concrete screed will also have insulation so I'm thinking no need to have further insulation between screed and the floor, and best have a gap, however small.

If I can make a screed work, it may well be the best and easiest way forward for me.

or a more complicated way , as it causes quite a disruption to plans, (willing to upset all and sundry if I really have to)

piers, every 1200 cm ( this seems to frequent to me ) 50 x 150 mm sole plates on the piers and crossed with 65 x 225 joists to nail into

further thoughts anyone..


rgds Bill

 

[Penners]

If you're going to put a screed down under a floating wood floor, there's not really much point to the floating floor (other than cosmetics). The whole point of the floating floor is to leave the earth beneath it bare, so that it can breathe. You then insert air bricks or vents in the outside walls, below floor level, to ventilate the void and carry away the damp air.

I would make the flooring joists deep enough to allow, under the T&G floor, an air gap and then tightly fitted insulation batts.

 

[BillH]

thankyou for your further input penners.. much apreciated.. Im leaning towards avoiding an argument and keeping the screed, but slightly different height to the origional plan.


if I am leaving a gap tween the screed and the floor, and vent that gap, that must do some good ?

will the polystyrene allow any damp collecting/pushed to the edge of the slab to evaporate ?

will redo the french drain, or no point in having it.

I know this is a little basic for the good minds of period property, but it's all the same principle and the place is old just not listed ,so a bit more leeway than normal may be allowed . . I hope you will bear with me as I have done my share of preserving the ancient and old here at home.


rgds & thnks
Bill

 

[Flyfisher]

I imagine that leaving a gap around the screed will help any damp evaporate into the well-ventilated space under the suspended floor and then out through the airbricks . . . in pretty much exactly the same way as it would if the screed was not present at all.

In other words, you'll be paying good money for a lump of screed that is serving no useful purpose except to avoid an awkward discussion with your builders.

The awkward discussion will be forgotten after a few days, perhaps a few weeks, but the useless screed will last forever.

 

[Penners]

Well argued, FF, and my sentiments entirely.

If you truly believe, BillH, that the screed is right for your building, then of course you should proceed with it. But not just to avoid an argument - that makes no sense.

A gap around the edge of the screed will, I imagine, allow a small amount of breathability, but not much. However, if you go and fill that gap with polystyrene, you will choke off even that small amount of breathability. Chuck a piece of expanded polystyrene on your bath water and see how much moisture passes through it!

 

[AMc]

My 2p'th.
A great big lump of concrete screed sounds like a bad idea in your circumstance and may well create long term issues that affect every finish you apply and the habitability of the house.
If you leave an air gap between the screed and the floor you might as well suspend the floor.
If you leave an air gap around the screed and fill it with polystyrene it will create a nice water tight seal and you might as well simply screed to the wall.

If you can then suspend a wooden floor with foam board insulation tightly fitted between the joists and air bricks below to allow cross ventilation underneath it. This will be quick and simple, shouldn't upset any builder with a chop saw and will be no more expensive than a delivery of ready mixed concrete.

I think 1200mm piers sounds about right, I certainly wouldn't go less than that unless the spans are pretty small as bouncy floors are rubbish. I would build brick piers with DPM on the top surface that you rest the joists on.

I know changing plans mid project is hard, but I really wouldn't go for a concrete screed unless you are really confident the subsoil is bone dry under any and all weather conditions.