Cancel the concrete ...

[fallingditch]

My cottage is lowlying on the Essex Marshes. No foundations, no DPC, no DPM. 50% of the floors are wooden - 50% old concrete. The wooden floors (20m2) are suffering from wet rot and need replacement. So seems to me, the advice offered by Groundworker (on 15 July 2005): "Cancel the concrete. Seriously, it's the wrong thing to do. Excavate the floor to 175mm below your finished floor level, pile in a few tons of 50mm down type 1 limestone, level it out to about 100mm thickness and wacker plate it thoroughly. Lay the flags on a bed of sharp sand. Set up some string lines in the room to level each flag individually by adjusting the quantity of sand by hand with a trowel. I'm guessing you should be able to get flags about 50mm thick but when you lay them like this they don't have to be truly consistent - you just adjust each bed of sand. It's a straightforward dry job, no concrete, don't bother with a dpm. Get a good heavy rubber mallet." is pretty sensible ...
If I am prepared to live with cold floors why would I want to do anything more sophisticated than this?

 

[biffvernon]

If you don't want to have cold floors then put a 100 or even 150mm layer of expanded polystyrene sheet underneath all that limestone. The limestone and flags will then act as a thermal store with the EPS preventing heat loss downwards.

EPS has good and bad points. There's discussion about it over on Green Building Forum

 

[RobT]

Hi Fallingditch,

to add to Biff's comments why not consider adding the Type 1 limestone then add a permeable membrane - similar to those used on drives to keep weeds down - then bed the flags onto a bed of lime and LECA (light expanded clay aggregate).

This system provides you with a breathing floor, but the addition of LECA provides the required insulation.

In addition to this ensure your external ground levels are well below your internal floor level to ensure any moisture around the property's walls can evaporate easily.

If you are nervous about the breathing floor concept I can vouch for it as I removed large sections of concrete flooring in a cottage I once owned and replaced it with floorbricks on lime and pamments on chalk & lime. The walls were also wattle & daubed and lime rendered to ensure total breathability.

Another plus for such floors is that in an area prone to flooding the water will, eventually, just drain away.

regards

Rob

 

[biffvernon]

Could either of you tell me what Type 1 (or any other type) limestone is?

 

[RobT]

Hi Biff,

as far as I understand the Type 1 aggregate I've used was a mixture of stone chippings plus a much finer material.

When compressed with a whacker I got a really even and smooth finish which was ready for the next layer of material e.g gravel for a drive.

The term Type 1 must be used as a trade name to describe stone chippings and finer material of a certain size mixted to a certain ratio.

regards

Rob

 

[CHRIS]

The full title is "Type 1 granular sub-base to the Department of Transport Specification for Highway Works" It is still referred to as MOT1 (the old Ministry of Transport) or even the more inaccurate "40mm to dust".

http://www.pavingexpert.com

Have a look on this website as it is quite good for these type of things, gives mixes etc. I know it is not a period property site but has some good info with regard to paving etc.[/url]

 

[biffvernon]

Ah yes, I'd forgotten about the The Paving Expert, an excellent site.

 

[Schoolmarm]

I haven't visited that site for ages but remember being highly amused by it last time.

 

[monkey writer]

That sounds very good - but if you lay down pamments - won't they stop the moisture from coming through? Or would you just lay them down and not fill the gaps between them?

 

[monkey writer]

hello, I would love an answer to this if anyone has one - assuming you lay down stone/pamments/tiles straight onto sand - do you then grout around the blocks or do you just leave them loose?

Thanks

 

[Mark]

either lime mortar or sand I think. Depends to some extent what flagstones/bricks/pammets you use, how tightly you pack them and what you bed them on.

you dont want them to move about so I used mortar on the soil for a small brick floor and your choice for flagstones.

that paving guide site is quite good, I didnt take the dig out advice becasue some of the walls seem to be a bit lacking in the foundation department and I didnt want to disturb anything.