Central Heating Pipes - Concealing

[Trommel]

I'm about to install central heating into a cottage I'm refurbishing.

For whatever reason, the upstairs floors are cement, so there's no space underneath to hide the pipes.

Will putting the pipes in the wall and filling over cause me problems with cracking plaster? One plumber has said, yes, another no.

I'm keen not to have them on view - apart from boxing them in, what are my options?

Thanks in advance.

 

[biffvernon]

Is it an old cottage. Cement floor? hmmmm, could be interesting

 

[Nemesis]

Lime ash?

From the Building Limes Forum:

http://www.buildinglimesforum.org.uk/Q&A.htm

Lime Ash Floor
Q I am interested in learning about installing a lime ash floor on the upper story of my strawbale house in Vermont, USA. would the lime ash be durable with in-floor heat (hot water with oxygen barrier pex tubing)? E

A It is very important to have the right mixture and consistency for the lime-ash and in particular to allow it to harden and dry out naturally before any heat is applied. This should be left for at least one month and ideally longer. Some would say that 'lime-ash' is often a misnomer for old floors, which were often made of gypsum not lime. Hydraulic lime would be safest for the binder, otherwise you need to be very sure of the pozzolanic qualities of any ash, brickdust etc used, as carbonation will only take place in the outer surfaces of the slab. RJS

A I have successfully carried out repairs to a lime ash floor using NHL 3.5 with brick dust, sharp sand and crushed charcoal added to replicate the appearance, but not the mix, of the original. Do you intend it to be left uncovered? If so, you can create a very attractive finish with the traditional mix (including quartz). We have treated ours with hard oil and wax which really brings out the colour and material variation. If you are happy with materials which are currently more easily available, you may want to use LECA (light expanded clay aggregate) in a layer under the heating pipes. This is very light (which will help with any weight issues) and also has good insulation qualities, so will direct heat upwards. We laid the mix onto reed, but straw may be more appropriate for you as you are using straw bales. RJS


And from PPUK Agony Uncle page:

SUBJECT: Lime ash floors should be as reliable as modern flooring materials
FROM: Richard Porter (Leicestershire)
I'm in the process of buying a cottage in Leicester. I am not sure of the age of the property but most in the area have thatched roofs. My main concerned relates to the material used for the upstairs flooring which appears to a mixture of plaster and hair. Would this be the original floor? I am concerned about its strength because it's damaged - could I replace it with a more modern flooring?

Richard Porter


What you describe may be a lime ash floor. These are relatively uncommon and an important feature. They are quite strong and if looked after can serve very well for many years. The SPAB have produced a leaflet on the repair of lime ash floors and there is an increasing body of knowledge relating to such floor structures.

You do not say whether the building is listed, but if it is then you will not be able to replace the floor without consent, which I doubt would be given. I suggest you look into methods of repairing the floor. There is no reason to suspect that a properly repaired lime ash floor should be any less reliable etc than a more conventional floor.

 

[NT]

I wonder if theres anything lime cant be used for.

NT

 

[NT]

denso tape, but I'm not sure if this is what you wanted to know or not.

NT

 

[Trommel]

I thought Denso tape was to prevent corrosion?

The floors are definitely cement rather than lime, most likely redone in the 60s from what I can gather.

Has anyone successfully plastered over central heating pipes (i.e. no dry lining)?

 

[GeoffP]

Hi Trommel,

I have an aversion to exposed pipes all over the house so as I renovate each room, I relocate the C/H pipes by running behind the skirting and under the plaster. The radiator inlet/outlet pipes now come out of the wall with only about 2 inches showing.
The only problem with this is that the valve sticks out horizontally rather than vertically.

I haven’t had any problems yet but I am told that plaster, whether lime or not, will eventually corrode the copper pipes but it could be 20 years before anything untoward happens.

To be on the safe side, my remedy for this is to use 10mm copper pipe where it exposed to the plaster and slip a length of ordinary plastic hose pipe over this and seal at the ends with tape.

I don’t know if this is the acceptable way of doing it but it works for me.

Geoff

 

[Penners]

I really don't think you have much choice but to surface mount and box in the pipes. If you take off the skirting boards first, then run your pipes along at mid-skirting level, you can replace the skirtings by simply fitting a bit of batten along the top and bottom to create a cavity behind the skirtings. It's not a bad solution.

As regards plaster cracks - yes you might get a few, but probably nothing that a bit of filler can't deal with.

 

[NT]

Isolating the pipe from the plaster allows differential expansion without cracking. Hence denso - or any other non-rigid wetplasterproof barrier.

NT

 

[Trommel]

Isolating the pipe from the plaster allows differential expansion without cracking. Hence denso - or any other non-rigid wetplasterproof barrier.

NT

Ah - I see ...

Thanks for the advice.

 

[Penners]

OK - by that method you might not get plaster cracks due to pipe movement, but I still reckon that, wherever you put central heating pipes in close proximity to a plastered wall, you're still likely to get a few cracks, because of the shrinkage caused by the drying effect of warmth from the pipes.

But nothing worth worrying about - bit of filler, bit of paint...

 

[Aidan]

Denso tape, wrapped with a 50% overlap, used to be the standard specification for any pipes that were to be embedded in walls or floor screeds. AS Nt said, it was to allow the pipe to move and alsoto prevent corrosion of the pipe.

A much better method now is to use plastic pipe-in-pipe.The outer pipe is a ridged flexible conduit which is embedded in the wall plaster. The inner pipe is smooth PEX, which slides into the conduit. With any water services (hot & cold, but not heating) the inner pipe must be removable to comply with the Water Regulations, and this is the only means I know of achieving that. You'll still get a large heat loss into the wall, so I'd only do that on an internal partition, never on an external wall.

Plastic Pex is good stuff, but it's liable to be gnawed by rodents and it expands a lot so can't be used fpr exposed pipe runs. I think we'll be seeing a lot more of it given that copper has doubled or tripled in price this year.

 

[Trommel]

Is there a reason why I couldn't simply chase out a channel behind the skirting boards, then replace the boards over?

Seems a simple solution ...

 

[Nemesis]

In general skirting boards should have a gap behind anyhow - the plaster shouldn't reach the ground.

We had pipes concealed in this way in a previous house and it was fine - no idea if there is a technical reason (apart from wood shirinkage) why it shouldn't be done however.