Taking/Breathable Floor - advice needed please

[acousticalfie]

Hi Everyone,

We have taken on a 300yr old cottage in need of desperate love and attention.

We are doing 1 room at a time as we have to live there. We know that we need to remove cement pointing and plastic exterior paint and have already started on small sections.

Anyway, the room in question is a small corner room. We have removed all the interior concrete water proofing from the walls and removed the damp carpet, damp underlay and 2" of asphalt waterproof bonding to reveal the original thinnish deteriorated flagstones laid on clay and bed rock. We have rebuilt the fireplace ready for a log burner but we are stuck with the floor.

Floor to ceiling is as low as it can possibly be and below flagstones are clay and bed rock with 18" thick walls built off bed rock in corners that cannot be disturbed. What we would like to know is if we dig out all clay around the bed rock is there a material we could use to help moisture and aid insulation? also we would really like a carpeted room but not sisal or coir. I have read about tanking 3/4 of the room with a stone edging laid with lime to give moisture somewhere to breath other than pushing moisture into the walls.

Any ideas or suggestions would be really appreciated.

Thank you.

Alfie

 

[88v8]

Hello and welcome.

How much depth do you have between flags and bedrock?

Ivor

 

[paulc]

What we would like to know is if we dig out all clay around the bed rock is there a material we could use to help moisture and aid insulation?

Foamed glass appears to be quite popular for limecrete floors - Whether this would give sufficient insulation would depend on what level you are aiming for and the available depth. Another option would be woodwool boards, but I don't know if they are recommended for floors.

As for carpets, I would have thought a hessian or felt backed carpet would allow moisture to pass through as long as there wasn't a layer of plastic embedded within the construction. Underlay helps to improve the feel underfoot, and again, felt might be an option.

 

[Flyfisher]

Foamed glass appears to be quite popular for limecrete floors - Whether this would give sufficient insulation would depend on what level you are aiming for and the available depth.

Another option is LECA. I used a LECA/NHL2 limecrete mix when replacing the hearth in a large inglenook fireplace. The hearth was laid directly on the earth and was between 8-10 inches thick, though only about 4 inches above the adjacent suspended floor. I finished the hearth with clay pamments fixed and grouted with lime mortar. This was only about three years ago, so early days yet, but all seems fine so far.

 

[acousticalfie]

What about Thermofloc?

Underneath the flagstones are high spots of bed rock but mainly clay. I am just looking for a material to back fill when all clay is removed. Hoping for a material that will aid insulation and help with any moisture coming through the floor.

Has anyone ever tanked 3/4 of the floor with a breathable perimeter?

 

[acousticalfie]

Hello and welcome.

How much depth do you have between flags and bedrock?

Ivor

Hello Ivor,

Bed rock is mainly in the corners. 1 corner 8" below floor level and in another corner the flags stones were directly on top of the bed rock with supporting wall built off it. It's a tricky one.

 

[88v8]

Part tanked.
It might work, depending how damp.
I'd do the 'tanking' with something removable such as bitumen, rather than something built in and irreversible. Just in case it's a bust.

Then as you say whatever damp there is will head outwards and has to be dissipated by breathability.

Therefore the perimeter needs a lot of exposed lime. Not only limecrete for the slab, but lime bedding, and lime pointing and a lot of it. So what I would recommend is a border of quarries, 6" or perhaps 4" depending on room size, at least 3 - 4 tiles wide. Fairly wide joints, say 1/4", pointed with NHL 2 and sharp sand. That will give a significant area of pointing and a highly breathable perimeter.
We have a chequerboard of black and red quarries around our sitting room for exactly this reason.

Needless to say, this does not make the damp vanish. It will 'breathe' into the room where it has to be dissipated by ventilation.
And any furniture you stand on it must have legs, not a solid base, or it will gather mould.

Carpet... well, a Turkey rug on felt underlay, but not over the tile border. Perhaps find your rug first, and then tailor the tile perimeter to take up the remaining space.
https://www.carpet-underlay-shop.co.uk/collections/carpet-underlay/wool-felt-carpet-underlay?gclid=CKKSkc6_0LACFVMetAodYTJrXQ
and
https://jenningsrugs.co.uk/collections/rugs

Insulation... where the limecrete slab has to provide support as opposed to just sitting on the bedrock, it needs to be at least 4" thick. That may not leave much for insulation. The classic underlayer is LECA, has some insulation value.
Talk to Ty Mawr or your local limecrete supplier.
This is Ty Mawr's insulated offering for underfloor heating, but it would work perfectly well unheated .
https://www.lime.org.uk/applications/sublimer-limecrete-floor-insulation-system.html

Ivor

 

[acousticalfie]

We may go for a parquet floor. Would we still use leco to fill the voids? and what materials would you use to lay and seal floor with?

 

[88v8]

If you lay parquet on a damp floor it will not last long. It will warp and eventually rot.
It was adopted in the late Victorian/Edwardian era when damp-proofing of walls and floor had advanced sufficiently to make it viable.

In your case, if you make the floor non-damp, the damp will head for the walls, as you previously commented.
This is what builders do with old houses, and then they sell the house to some unfortunate mug, who eventually appears on this forum.

Parquet - whether you really mean parquet that is to say wood-blocks, or some modern substitute - is not suitable for a house with neither dpc nor dpm.

The moisture is there. One can't wish it away. It can either be shut out, which usually fails, or allowed to breathe into the house and dissipated.
Sorry.

Ivor

 

[Pennyviz]

This house doesn't have a dpm or dpc and I've just discovered a parquet under the carpet in the sitting room, Not looking too bad, guessing mid Victorian, but quite large gaps - I too was wondering how best to fill and finish ......

Penny

 

[88v8]

This house doesn't have a dpm or dpc and I've just discovered a parquet under the carpet in the sitting room, Not looking too bad, guessing mid Victorian, but quite large gaps - I too was wondering how best to fill and finish ......Penny

Interesting. Solid floor or suspended?
On a suspended floor, the parquet is isolated from damp.
On a solid floor it will almost certainly have been bedded into hot bitumen, which itself constitutes a dpm.

As to filling, Toby Newell would be the man to answer that one.
http://newellwoodworks.co.uk/about%20us.html
There are a few past topics if you search on 'parquet gap'.
Perhaps start another thread.

Ivor

 

[malcolm]

I have a Parquet floor installed about 1910 in a room dating from around 1600 so no damp course. It has a 1 inch concrete floor that the Edwardians put in over earth. The Parquet is bedded in bitumen. I had to remove some of it due to rot, but I think that was due to exterior ground levels being much too high. I think I'll get away with reinstating the Parquet now the ground levels are fixed. Mine is very tightly joined and away from the walls it is still very good.

 

[MatthewC]

We may go for a parquet floor. Would we still use leco to fill the voids? and what materials would you use to lay and seal floor with?

You should investigate whether a part limecrete floor would work. Where you have bedrock (type?) then clearly any water will flow downhill to wherever you don't have bedrock, won't it? Hence if you can do limecrete on enough of the floor I think it would still work.

A limecrete floor is designed to use a base (e.g. LECA or RFG) through which water vapour can penetrate but water cannot rise by capilliary action, with a slab of lime mortar on top. My limecrete floor has a layer of a breathable base (LECA but if doing it again would use RFG as it is easier to lay and can be tamped). Then it has a layer of NHL (5, I think, but possibly it was 3.5) mixed with LECA, a layer of mortar (the same NHL and sand), a 50mm bed of mortar and then limestone flags on top of that, for a total depth of approx 400mm. Yes, it's a long way to dig, and possibly using RFG you might save a couple of inches of digging as (I think) the slab is just mortar.

You wouldn't want to seal the surface of a limecrete floor as water vapour has to be able to pass through the whole thing, rather than collecting as a pool of water which eventually reaches your walls and wrecks your plaster (hence the futile attempts using cement on the wall to overcome THAT problem!). Therefore if you fit parquet on bitumen it will seal the floor... It goes without saying that other damp issues such as high ground outside and water pouring down the walls should be fixed first.

Personally I am not aware of any other solution which permanently sorts out a damp floor other than a limecrete floor but, seeing as I installed a 20 sq m one five years ago, I would say that, wouldn't I? 8)

 

[Pennyviz]

This house doesn't have a dpm or dpc and I've just discovered a parquet under the carpet in the sitting room, Not looking too bad, guessing mid Victorian, but quite large gaps - I too was wondering how best to fill and finish ......Penny

Interesting. Solid floor or suspended?
On a suspended floor, the parquet is isolated from damp.
On a solid floor it will almost certainly have been bedded into hot bitumen, which itself constitutes a dpm.

As to filling, Toby Newell would be the man to answer that one.
http://newellwoodworks.co.uk/about%20us.html
There are a few past topics if you search on 'parquet gap'.
Perhaps start another thread.

Ivor

Hi Ivor
Yes solid - oldest part of house with roof dating to about 1350, probably is onto bitumen as I've found it on one of the walls, however it isn't under the quarry tiles which were probably put in at same time in hall, so I will have to some further investigating.
Penny

 

[acousticalfie]

New idea......

How about removing as much clay as possible around the bedrock and back filling with foamed glass to create an even surface. Some clay voids are 1m deep some are a few inches. Then tamped down as much as possible.

Then a NHL 5 and sand 3:1 mix to lay new flagstones on top with the same nhl mix as joints. It would need to set as fast as possible as it's a walk through room.

Then a breathable sealer with a wool rug.

Thoughts?

 

[88v8]

Yes.
Lay some of the flags, then point them, then the rest, so you'll always have a pathway..... statin' the bleedin' obvious...... and if you use a mixture of stone dust and sharp sand for the pointing it will go off quicker. Pointing needs to be well pressed in and battered with a churn brush.

However, I don't think there's such a thing as a breathable sealer. Contrarywise, doncha know.
Hmm, we've debated this before, hmmm
http://www.periodproperty.co.uk/forum/viewtopic.php?f=1&t=15328&p=210638&hilit=sealer+flagstones#p210638
and others by searching on 'sealing flagstones'.

Now, it wouldn't be a great sin to seal the flagstones, given that a stone floor - or a stone wall - breathes primarily through its joints, but don't seal the pointing in any way or you will really have defeated yourself.

Ivor

 

[acousticalfie]

Are there certain types of flagstone that will help or be more beneficial? As I have heard about salts coming out of certain stone if they become damp.

Maybe a porous stone would help release any moisture more evenly across the floor if unsealed?

 

[Pennyviz]

I've used ltp mattstone H2o,on my quarries, supposed to be designed for floors with no dpc

http://www.ltp-online.co.uk/prod/ltp-matt-h20

Penny

 

[88v8]

Are there certain types of flagstone that will help or be more beneficial? As I have heard about salts coming out of certain stone if they become damp. Maybe a porous stone would help release any moisture more evenly across the floor if unsealed?

You need a stone expert here, which I'm not, but any stone wall or floor breathes primarily through its joints so I think the choice of stone would in that respect be marginal.

Even concrete imitation stone would work, provided it's laid and pointed in lime with fairly wide joints.
We used Organicstone's ersatz Painswick in one room, with a quarry tile border, and it works fine.
https://organicstone.com/product-ranges/atelier-antique-stone-flooring-ranges/

Ivor

 

[Zebra]

New idea......

How about removing as much clay as possible around the bedrock and back filling with foamed glass to create an even surface. Some clay voids are 1m deep some are a few inches. Then tamped down as much as possible.

Then a NHL 5 and sand 3:1 mix to lay new flagstones on top with the same nhl mix as joints. It would need to set as fast as possible as it's a walk through room.

Then a breathable sealer with a wool rug.

Thoughts?

But if your flagstones are original then you wouldn't want to replace them, would you? And if they haven't been sealed this last 300 years, then why seal them now? Otherwise, your plan sounds like a good one - digging out the clay and replacing with foamed glass. Are you thinking of doing away with the limecrete layer though, and laying the flagstones straight on the foamed glass? I haven't heard of this being done, but I suppose on top of bedrock it's not like anything's going to move. I think NHL5 would set fast enough to walk on within a few hours, if you weren't too heavy on your hooves. You could always plonk a piece of old carpet and a sheet of ply on top as a load spreader til you're sure.