Floor and Heating Advice Please

[Brightonian]

We recently bought an old farmhouse early 1700 and 1800’s. The outside was higher than the inside floor (14 inches) and was originally built into a hill. So far we have lowered the level outside to the same height as the floor (didn’t want to go lower because of the lack of foundations although the builder tells me it appears to be built on bedrock) and put in a retaining wall two metres away from the gable end of the house which faces a rather steep hill with a French drain at the bottom of the wall.

The gap between the wall and the house has been gravelled and the down-pipes have been diverted to soak-away. This appears to have made a huge difference to the floors inside and they are now drying out – previously they had a puddle !

Now turning my attention to the inside. The existing floors appear to be made of concrete and lime dust. Current thoughts are to:

• Replace all the hard floors with limecrete or
• Put in a hybrid floor with concrete in the middle and limecrete around the edges
• Install UFH

Issues and concerns around this include:

Expense
• How much more expensive are limecrete floors generally than concrete ones as a rough percentage (I have circa 60 m2 to do)?
• How much would be saved by using LECA (lightweight expanded clay aggregate) as opposed to recycled glass and what would the differences be in the corresponding u values (negligible relative to the expense or worthwhile)? Plus would it adversely affect the finish if I went down the polished limecrete route (is LECA better than glass or vice versa)?

Breathability
• Are the advantages of breathability overplayed particularly when the limecrete is covered? Even the flagstones I have for one of the floors would leave a very modest area with joints.
• What practical floor surfaces (not easy stained or dusty) could be used to preserve the breathability of the floor?
• Can limecrete be polished to provide an acceptable/aesthetically pleasing and practical finish ?

Hybrid floor
• Is it a practical solution in terms of both of the above – gets breathability to where it is needed most (the outer edges) and minimises costs?
UFH
• Would limestone bedrock be an inhibitor or would it actually help if left in place / incorporated within the floor where possible (seen as part of the insulation/slab)? We had to dig/drill loads out from the outside when putting in the drains! If it helped or was neutral, it would cause significantly less disruption to the building and save on both time and materials
• How well does the building have to be insulated to make UFH worthwhile (I was intending to put radiators upstairs and include some downstairs in addition to the UFH). The plan was to heat the building via a boiler stove and an oil boiler (although looking into GSHP). Is it a case of every little bit helps or the benefits of UFH largely negated if you have to install radiators as well?
• Finally can UFH easily deal with floors on slightly different levels (anything to be aware of) and what does it typically cost over and above the cost of installing the floors and the screed?

Any tips and advice on the above, including recommended suppliers, would be greatly appreciated.

Many thanks
Har

 

[Zebra]

I can't help with costs, but can recommend Ty-Mawr (www.lime.org.uk) or Mike Wye (www.mikewye.co.uk) as suppliers. Both will offer advice over the phone. As you have only just carried out your extensive works with the ground level and the drainage, is it possible to give it a year or so to dry out, and see what the situation is? It may be that you no longer have a damp problem, and can leave the existing concrete floor. But it may be a bit of a trial and error approach, to find out the right solution.
I had all of the problems you describe - ground level higher outside than inside, concrete floor, as well as wet walls.
I dug a trench adjacent to the house, similar to what you describe, put in effective rainwater drainage, and still had wet walls. I dug up the concrete floor around the edges, leaving bare earth exposed underneath. Still wet walls. This is how I learned that a breathable floor was not going to solve the problem for me, but I didn't know that until I'd tried all the above methods.
It may be that your house will dry nicely and you won't have to dig the floor up, but you'll have to give it time to dry out after taking each remedial measure, in order to know whether you have solved the problem now, or have to look further into it. Whether or not you need a breathable floor depends on how much dampness you have underneath, and where it will end up if it can't come through the floor.
Sorry if this is a bit of a ramble and doesn't make much sense, I'm sure someone more experienced will be along soon.
I decided in the end not to go for UFH because I'm not here all the time, and I'm too stingy to leave the UFH on when I'm out, so I want radiators, which will heat the place up quickly when I get in. UFH takes longer to make the place feel warm.

 

[plasticpigeon]

I have put in a limecrete floor. It was around £1200 which included foamed glass hardcore, aggregate for the limecrete, lime, textile,grout and delivery. It also included enough lime for bedding quarry tiles, but I had 8 bags left over so got more than I needed. This was for around 15m^2. It took 2 people 2 days to lay, one easy day for the foamed glass and to compact it, and one tough day mixing the limecrete and laying. I had an interesting chat with a guy at Ty Mawr who said that the foamed glass and limecrete slab act as a moisture buffer or sink, that ground moisture can move into and out of as the ground conditions change, so even with an impermeable covering it is still effective. Not sure how much I believe that, but it is something to consider.

 

[MatthewC]

Welcome, Har

I too have laid a limecrete floor - about 20sq m, using LECA (see my blog {blue spot on right} for April-May 2011). Off hand I can't say how much it cost (£2k-£3k??) but I bet it was at least double the cost of (wash my mouth out) concrete. I also recommend Mike Wye - they were very good at answering detailed panic questions halfway through the job, as well as giving me the basic design. Ask them for a quote for that floor area and they will do the sums (which were more accurate for me than PP's figures). NB If you do their one day lime course, you get a discount off products.

You ask lots of questions but I can only answer a few bits: I am sure than you can't polish LECA as it would crumble - it's not designed to be on the surface, and I might well use RFG if doing it again. I put in a small amount of electric UFH as I wanted to have warm feet in my kitchen on winter mornings, and it has never got cold enough for me to need to switch it on (except to test). On the same theme, I am convinced that my limecrete with black limestone flags (30-40mm) is intrinsically warmer than concrete with ceramic tiles. I have not treated or sealed the flags, they just get swept often and washed with water and a sponge about every six months. They sort of "wear-in" and really look as though they have been there ages - although they get a dusty finish, it doesn't seem to matter.

You say the exterior ground level is the same as the floor level - ideally you need a difference of about six inches, so you might find that the base of the wall still gets damp. If it does then I don't think that you will question whether the breathability is "overplayed".

I don't know about hybrid floors as I never heard of such a thing when planning my floor three years ago. However, if you intend to live in your house for ages then I am sure that you will get value for money by spending money on decent floors.

Good luck

Matthew

 

[88v8]

Replaced a concrete/dpm floor with limecrete. Previously, the perimeter was so damp the gripperods had rotted. Now it's dry.

Floor was 12' x 15', cost around £4,000. Materials came from Ty Mawr, these chaps did the job.
http://www.brownstoneconstruction.co.uk/index.html#5

Don't use any old builder, especially those who think 'lime' means the hydrated stuff they use as a plasticiser.

On our floor we put bogus Painswick slabs from here
http://www.organicstone.com/content.aspx?m0=2
Painswick was used for flooring in the Houses of Parliament, but the quarry is shut.
These are made of reconstituted granite in a cement matrix, with a 3M resin coating. Smooth surface. They look old, because each one has been moulded from an old original. Superb.
Cost around £170/m.
I see they're not mentioned on the website so you'd need to check they're still being made.
The slabs are not breathable, so... we bedded them in cement but left quite large joints and pointed them in NHL5/sharp sand. And, we put in a 12" perimeter of 6" quarries so as to get more joints, bedded and pointed in NHL5.

You're perfectly correct, a stone floor breathes 90% through the joints.

Underfloor heating... was installed in a GII house just up the road. Rather reminds me of storage heaters, about as responsive. A sudden cold snap, they have to get out their thermals while the floor heats up, a warm day and they're opening the windows. Huh. Perhaps as low-level background heating, with another system overlaid. Or perhaps not at all

Ivor (who doesn't do technology)