Lime plaster & wiring

[Liz Fry]

OK, we have almost finished stripping the tanking and cement render from our limestone built cottage................(see pic)

I`m now allowing myself the luxury of thinking about future considerations such as wiring plumbing etc. I would like to hide as much of the wiring and pipework as possible rather than having them surface mounted. I`m a little concerned however about the interaction of wiring/plastic trunking etc with the lime. Does anyone have any thoughts/experience on this?

Any comments would be appreciated.

k rgds

Liz

 

[Gervase]

The PVC sheathing on the wire is fine with lime, but I prefer to put plastic trunking caps over the wires when plastering. Again, it's inert and doesn't react with the lime, but it also leaves the wires free to move a little, so that when the sparks does the second fix you don't get your plaster cracked - and it avoids the huge irritation of snagging a cable clip with your trowel when plastering.
It's best to chase the stone with something like this, particularly if you're fitting pipework, so that you don't have to plaster too thickly. Copper pipes should be wrapped in heavy-duty polythene if they're to be plastered over, otherwise they'll corrode. If you're using Hep2o or similar butyl pipework, then you don't have to worry.

 

[MdB]

It's best to chase the stone with something like this, ...

I'm sure chasing stone walls is something that the CO would have something to say about, but if you are going to do it, then a wall chaser is an essential buy. My £40 one would have been worth getting for one cut let alone the dozens I have done/need to do. Combined with a vacuum cleaner the amount of dust is reduced to more manageable proportions compared to an angle grinder. (top tip, if using one to cut a channel for ducting or a pipe, run it down the wall by eye, don't be tempted to use a straight edge or similar. The slight wobble enables the ducting to be jammed in place rather than it always falling out.)

 

[Cloudscape]

I have this feeling that I had better remove the galvanized capping (installed over cables by my electrician, in areas where the cables will be plastered over) and replace it with plastic? Are galvanized trunking and lime a bad combination?

 

[Andrew Bodenham]

Galvanised capping / trunking / conduit should not be a problem with any type of plaster, as corrosion will only occur in wet conditions. However, if you're installing on an outside wall where you know that dampness / condensation etc. might be an issue then it would be sensible to use plastic alternatives. Before anybody says, I know that plastering is a wet business, but the amount of corrosion that would occur during the application and drying phase would be negligible, in my opinion.
I use plastic oval conduit for plastered-in wiring, extending it into floor void or roof space as appropriate. It makes feeding in cables a doddle, and later wiring revisions are equally easy - useful when jobs are being done piecemeal on a room-by-room basis.

Gervase's comment about plastic pipework reminds me of a recent case I saw where mice ate through plastic CH pipes, causing considerable flood damage. That certainly reinforced my Luddite view of non-copper plumbing systems....

 

[vicky whitworth]

This post has raised yet another question for me. We are about to have central heating installed and my plumber has told me that I can't have the central heating pipes chased into the walls and then plastered over as 'they don't like it these days'. I have to have the pipework exposed and running down and along the walls. I presume by 'they' he meant building control. The cottage isn't listed. I'm not totally adverse to having the pipework exposed but would have liked the option to chase it in. What's the view here on this? Many thanks, Vicky

 

[MdB]

I have this feeling that I had better remove the galvanized capping (installed over cables by my electrician, in areas where the cables will be plastered over) and replace it with plastic? Are galvanized trunking and lime a bad combination?

People use plastic capping as galvanized capping has to be earthed to meet the regs which is a pain to do.

 

[Ian Bond]

This post has raised yet another question for me. We are about to have central heating installed and my plumber has told me that I can't have the central heating pipes chased into the walls and then plastered over as 'they don't like it these days'. I have to have the pipework exposed and running down and along the walls. I presume by 'they' he meant building control. The cottage isn't listed. I'm not totally adverse to having the pipework exposed but would have liked the option to chase it in. What's the view here on this? Many thanks, Vicky

In simple cottage properties like mine, I prefer to have the pipes exposed but installed neatly and painted. Better than poorly done boxing in. The problem is worse if you have work around architectural features, such as cornices. I'm sure many of us have seen brutally hacked out pipe and cable runs. I've done some boxing in for cables in a better room, and replicated timber cornice, picture rail and skirting, but it has to be done to perfection, otherwise will look dreadful.

You may also have a handy cupboard or some other discreet corner that would make a great place for hiding some of the pipe runs .

Don't know about your house, but in mine the plaster follows the uneven rubble stone walls, and is 1/8 of an inch thick in some places, and 2 inches thick in others on the same wall. Chasing is a nightmare in hard stone too.

I exposed some 40 year old plus copper pipes that had been under gypsum plaster, and they looked OK. In fact, they're still in service for the domestic water supply, but hidden behind a timber panel over a door. I've no idea what lime would do to copper tube.

Andrew's methods of using oval tube for cables is a good idea too, and something I've also had a go with. It's a bit of extra effort to prepare the route, but it certainly makes later repairs and alterations a little easier, and potentially less messy.

 

[shelli]

This post has raised yet another question for me. We are about to have central heating installed and my plumber has told me that I can't have the central heating pipes chased into the walls and then plastered over as 'they don't like it these days'. I have to have the pipework exposed and running down and along the walls. I presume by 'they' he meant building control. The cottage isn't listed. I'm not totally adverse to having the pipework exposed but would have liked the option to chase it in. What's the view here on this? Many thanks, Vicky

Ours is chased into walls and plastered over - our cottage isnt listed - I wouldn't like to have all the pipework exposed down walls and have to box it in - just makes ugly unnecessary joinery in places where you probably want to put useful things like furniture next to walls

 

[Ian Bond]

Which part of the regulations is he referring to - Part A, Structure?

I can't think of rule that precludes putting pipes into wall chases , providing they are not excessively weakened as a result (see Part A). Or perhaps for problems associated with leaks or future maintenance. Shouldn't be a problem if done properly, and Gervase has covered this in his earlier post.

Chasing into the walls does create a lot of additional work (and mess though), so I can understand why perhaps someone would try to dissuade you.

 

[chuckey]

Plastering central heating pipes is dodgy as the pipes contract/expand while in use. They could flex and crack the plasterwork. They should be wrapped in layer of thin foam so they can move about.
Wiring. When I removed the plaster in a cottage and its ONLY down stairs 13A socket, the wiring dropped from the ceiling and was covered by one of those galvanised channel strips and plastered in. The strip was nailed on using galvanised nails one of which was carefully hammered in the centre of the strip straight into the cable within. I still have that piece of cable complete with smoke marks around the nail hole in it. The socket worked, I still wonder if the whole strip was "live" or earthed via the nail.
The british tradesman strikes again (or at least his father)
Frank

 

[Moo]

I have a dim memory of Nemesis (or was it Evelyn?) advocating surface mounting and being vehemently against chasing-in.

 

[Nemesis]

Really? Dim it is then.

It all depends on the property and the significance of what would be destroyed. In the case of important and historic, then clearly surface mounted is less destructive. Clearly, there's little of historic significance plasterwise to be now destroyed in the pic posted.

 

[Pford75]

Irrespective of whether lime plaster is okay with the plastic sheathing of the cable.....most professional electricians should suggest the use of conduit. It's much safer for anyone who subsequently does any work on your house and the cost and effort is not large (given that it looks like you've done the messy bit).

With plumbing, I've always been torn between the desire to hide pipework where possible and the need to be able to get to it in the even of leaks etc.

 

[Cloudscape]

In the case of my house, I've allowed the electrician to chase the cables in, because most of the artless hacking is being done on walls where I intend to remove the gypsum. I would never have started chopping lumps out of the walls (definitely not yet), so I stood back and let him do it. Now I can see exactly what the layers of plaster are like on the walls he's attacked. I didn't allow him to chop away any stone.

 

[DaveBrigg]

Our plastic pipework downstairs was clipped to the exposed brickwork before being plastered over, and we've had no problems so far with cracking. This was less destructive than lifting the floorboards.