Sub floor on marl ground - concrete needed?

ditpaintball

Hey Guys,

Currently renovating a 300 year old farmhouse what was built on hard marl ground.

I have taken up an old concrete floor floor that was put in 80 years ago and I am back down to superhard and dry marl ground.

My plan was this, from top down:

- 60mm Easy screed with UFH
- Plastic Layer
- 150mm PIR insulation
- Heavy Vapour / Radon barrier
- 100mm 804 whacked down
- Marl Base

The house has been there 300+ years, solid stone walls. So I can't see there being any movements or shrinkage in ground. Do I need to have a concrete subfloor or is my plan seem ok?

There will be a 100mm boarder of limecrete around all the walls, from floor level to footings to allow for some vapour transfer.

gk5000

Hopefully someone shall be along to advise, as I'm also interested.
One thing, I think there are new versions of 804 ; T1, T2 or T3 which are certified pyrite free.

However, my question to you: did you have any problems digging down near the walls without disturbing the foundations/footings?

BryanF

What are you doing about dpc at the walls

Calahonda52

it wont be 804, not permitted as hinted by gk5000.
need sand layer on top of the stone
how will you comply with radon ventilation requirements
you may get no warranty on the UFH without the slab
use 200mm pir

ditpaintball

gk5000 wrote: »

Hopefully someone shall be along to advise, as I'm also interested.
One thing, I think there are new versions of 804 ; T1, T2 or T3 which are certified pyrite free.

However, my question to you: did you have any problems digging down near the walls without disturbing the foundations/footings?

No problem digging down to the footings. The footings are 1m wide and built on solid marl. The wall itself is 800mm thick.

The original floor was a red brick in a bed of lime mortar with was just above the footings anyway. The hardest part was removing all the 500mm of rubble that thrown on top of it to raise the floor level.

ditpaintball

BryanF wrote: »

What are you doing about dpc at the walls

No DPC at the walls, It will be a hybrid limecrete floor. Limecrete boarder along the walls (footings to floor level) and the insulated floor and screen on the side. The DPC will terminate at the limecrete boarder.

The house survived pretty well for 300 years without a DPC. All original drains outside house are working fine.

ditpaintball

Calahonda52 wrote: »

it wont be 804, not permitted as hinted by gk5000.
need sand layer on top of the stone
how will you comply with radon ventilation requirements
you may get no warranty on the UFH without the slab
use 200mm pir

I am installing the UFH my self, so there will no issues with warranty.

In terms of radon, I will put a sump and pipe in anyway, but it might be fairly pointless. It's a 300 year old house, rubble walls are not really airtight. So if there is a building a build of of radon it has plenty of ways out.

thebigmc

ditpaintball wrote: »

My plan was this, from top down:

- 60mm Easy screed with UFH
- Plastic Layer
- 150mm PIR insulation
- Heavy Vapour / Radon barrier
- 100mm 804 whacked down
- Marl Base

I'm planning a similar floor myself soon and interested how it goes for you. Is doing UFH by your self straightforward or are you experienced?

Do you need the Vapour Radon barrier? Since you are using the vapour open limecrete at the perimeter, I don't think you do.

Did you have a micro digger or how did you get the old concrete floor and fill out?

ditpaintball

thebigmc wrote: »

I'm planning a similar floor myself soon and interested how it goes for you. Is doing UFH by your self straightforward or are you experienced?

Do you need the Vapour Radon barrier? Since you are using the vapour open limecrete at the perimeter, I don't think you do.

Did you have a micro digger or how did you get the old concrete floor and fill out?

I'm not a plumber, just fairly handy at DIY. I have already replumbed the upper floors of the house and got old steel rads going. UFH is not that simple a job, but I have all the gear and the equipment supplier does the design, so it should be ok.

I am also looking at GeoCell for insulation and hardcore, but that means a full limecrete floor and it roughly double the costs ( €5K in my case for 110m2).

As for the barrier, I will need sometime to keep the insulation dry and stop the screen getting damp. A radon sump is only a few quid, so I might as well put one in.

As for digging the concrete, here is a video of some of it:
https://www.instagram.com/p/CKzuorNHVYx/?utm_source=ig_web_copy_link

dathi

ditpaintball wrote: »

As for digging the concrete, here is a video of some of it:
https://www.instagram.com/p/CKzuorNHVYx/?utm_source=ig_web_copy_link

great photo the circular cobbles look like base of a ring cairn any ideas what it was there for ?

ditpaintball

dathi wrote: »

great photo the circular cobbles look like base of a ring cairn any ideas what it was there for ?

We are not sure what it is. The conservationist or the OPW don't know what it is either.