Floor construction options?

[Jake]

I have an attached building of random stone construction, which is listed.
It has had planning permission in the past to incorporate it into the main house. The present floor is little more than dirt and dust with clay beneath.
Looking at the approved drawings organised by the previous owner, there is a large amount of excavation of the floor proposed in order to get depth. It is then built up and a concrete slab laid.
There is so much excavation proposed for the floor that the annotated drawings identify further excavation under the main walls to effectively insert new footings. However there is absolutely no problem with the main walls.
It seems a bit barmy to start compromising the integrity of the main walls for the sake of a concrete floor.
The current floor level is about the same as the main house and there are no real damp issues that a damp proof membrane could not remedy within a new floor construction.
What floor construction options might be possible that would involve considerably less excavation than a typical concrete floor ?
I have no preferences in terms of a floor finish, so any suggested solution or system would be a consideration. Cheers.

 

[Schoolmarm]

Leca and limecrete

or

Suspended wooden floor

or


Flags or tiles laid on lime mortar



Nooooooooooooooo to the damp proof membrane

 

[Jake]

Thanks you very much for the reply.
I have had a quick look at the Leca and Limecrete suggestion. That looks a very interesting solution.
However, it still looks as though considerable depth would need to be excavated to handle the required layers. I would need to check.
As this would be a new floor construction rather than me managing an existing arrangement I presumed that I would have to meet building regs by putting in not only a dpm but also insulation. Is that the case?
Those elements in themselves do not cause a particular issue in terms of depth.
I am managing penetrating damp in other parts of the house through natural ventilation, and the use of appropriate materials, so I appreciate how effective such methods can be. So whilst I think say tiles on lime mortar would be attractive and manageable, I thought that the structural characteristics would not meet building regs, in addition to the dpm and insulation issues.

 

[Schoolmarm]

And that is the bit I never understand. Building regs grrrrrrr.

Hopefully an expert will come and answer soon

 

[Moo]

Flags or tiles laid on lime mortar

You don't even need to bother with the lime mortar. Lots of us have flags and/or pamments laid straight on to earth and pointed with lime, and they work a treat.

 

[MdB]

Flags or tiles laid on lime mortar

You don't even need to bother with the lime mortar. Lots of us have flags and/or pamments laid straight on to earth and pointed with lime, and they work a treat.

If the current dirt floor is dry then this does sound like a good solution. However, if it is a change of use, building control might insist that the current thermal regs are met. I'm not sure on this - speak to them. This would normally mean insulation everywhere including the floor but you may be able to get around this if you have good insulation elsewhere and use a very efficient heating source (like a heat pump). If it isn't a change of use and it used to be lived in, then I believe building regs don't apply, but again I'm not sure on this.

As the building is listed, you also need to speak to the CO who may well have their own ideas and I believe overrule building control.

 

[Essex]

We successfully installed a limecrete floor without a dpm, with the assistance of our conservation officer, who convinced building control that it was suitable. I believe that there are other examples of building control agreeing to this.
We are now two years on and are dry as a bone.

 

[Jake]

Hello Essex, from the various replies there are some useful perspectives for me to explore.
In your particular case, can you remember to what depth you excavated to enable your Limecrete solution?

 

[MdB]

Hello Essex, from the various replies there are some useful perspectives for me to explore.
In your particular case, can you remember to what depth you excavated to enable your Limecrete solution?

I seem to remember, when I looked into it, that a limecrete floor with LECA has to be around 400mm deep to have a good U value.

 

[ljn]

I have had a limecreate buildup of 465 mm specified by http://www.limecrete.org.uk/
it includes a 190 mm LECA expanded clay insulation layer suitable for underfloor heating. (cheeper then the glasscreate option)
The floor buildup gives a U-value of 0.25W/m2K which should meet building regs.

Hope this helps.

My question: has anyone done this? My fear is that with winter on it's way, I'll be left with quicksand in the basement all winter with my builder telling me "I told you so" ... Essex? how long do I need to allow?

 

[Essex]

We are on good Essex clay and we lived with the clay exposed as the floor through the winter. They remained bone dry. We laid the breather membrane, LECA, breather membrane, limecrete (with LECA aggregate) and lime screed with U/F heating topped with york stone slabs in the summer two years ago. It appears to have worked well, we are very pleased with it.

 

[ljn]

Essex, Do you remember how long it took for the limecreate screed to dry so you could lay the underfloor heating and york stone topping?

 

[Gervase]

You can usually start work on UFH, screeding and the like after about 10 days. The slab will continue curing and getting stronger for some weeks, but provided it's kept frost free and the temperature is above 5 degrees, it will be strong enough to work on before a fortnight is up.

 

[Essex]

From memory, about three weeks

 

[ljn]

I have spoken to the guys at limecreate.org.uk

They say pour the screed, allow 2- 3 days before walking on, but lay planks to spread the weight. 4-5 weeks to cure.

Then lay the glass create screed (embedding the underfloor hating pipes). This layer also requires a couple of days before walking on and 4- 5 weeks to cure.

A bit scary as it will be the middle of winter by the time I get listed building consent.

They say it should not freeze, but also say you shouldn't use heating. So it will freeze. But what if I just place a heater to make sure the room is above 10 degrees? No, no heating. So basically, the advice is to wait for spring. By then, even if capitalism as we know it might not be over, the mortgage company isn't going to be happy about the empty shell that should be a kitchen. not to mention getting all trades back to do a second phase. Ouch. Maybe I'll have to give in to the builder and his kingspan /concrete.

 

[Schoolmarm]

We are highly unlikely to get frost so bad that it goes into the floor of a building. You could lay rolls of the silver/plastic covered loft insulation down (the thick fluffy one) down loosely to protect it.

It seems a shame to rush just to keep the mortgage bods happy.

 

[skier-hughes]

the mortgage company isn't going to be happy about the empty shell that should be a kitchen.

Why?

Is it a condition of the mortgage that it gets done within a certain timespan?

If so, speak to them and explain what's happening, that work is progressing, but to ensure that their assets are well looked after then this is how it needs to be. Ours was fine with the delays we had, so long as we kept them informed of what was happening and when.

Graham

 

[MdB]

Maybe I'll have to give in to the builder and his kingspan /concrete.

We went down the concrete / DPM / insulation route. In my defense, most of the house is modern and we could get the DPM under most of the walls so it made sense and was quite a bit cheaper (and quicker to install). One thing we have done is to leave a gap next to the old walls which will be filled with limecrete so that moisture in those areas has a larger area to evaporate from. This should hopefully stop too much moisture being pushed up the old walls.