Electrical chases plus Gypsum DPC repairs

[Milfry]

Hi,

recently purchased and started renovating a 1900 Stone property and trying to figure out a couple of solutions:

1/ Had the house rewired so I need to make good all of the chases left by the electrician - original walls are lime plaster (with hair) from what I can tell and the electrician has cased all of the cables in plastic capping, some of which is not that deep into the chase. I have read somewhere that interior pollyfilla can be used as it’s similar to plaster of Paris so is quite breathable? Anyone used this successfully? Just conscious of something adhering to the plastic otherwise would go bonding/easifill. Or would easifill in layers work out ok with the chases not taking up much of the actual walls. Also gone through a couple of laths upstairs so ideally want the same product to repair all of the damage if possible.

2/ Looks like the previous owners had a DPC installed and then replastered the walls up to around 1m in gypsum - should i hack this off while I’ve got the chance and replaster in lime base and then lime skim coat or wI’ll the rest of the wall still being original eliminate any potential damp issues?

thank you

 

[RBailey]

I would be more concerned with the lower levels, previous owners had the damp wally in and have gypsum over the lower 1m of a lot of rooms and most of it is blown.
I am re-doing this in lime as I work my way around the rooms. BUT my first concern has been to solve the source and had blocked drains (solved), leaking gutters (solved) and high ground levels (partly solved).

You may not need to replace 100% of the gypsum, depends on how bad they are as well as money, time and future disruption.

Cheers,
Richard B.

 

[Stevers]

1/ Plaster of Paris is just a finely divided gypsum plaster. Polyfilla is silica with a cellulose base, and although I'm not at all sure what that means, I only ever use it as a fine surface filler. Gypsum plasters have issues, but I'm dubious that a lack of 'breathability' is one of them. Gypsum plasters really don't like damp though, particularly where there are salts. Nevertheless I have used Thistle One Coat for filling the many chases above ground in my 1879 stone house and all of those have been absolutely fine after 25 years. This has been true even where the neighbouring original lime plasters had already blown slightly. Thistle One Coat is more open textured than pink finishing plaster, it doesn't polish so easily and the pros aren't keen on it for that reason. For older houses open texture is good and it's a good match for the lime plaster in appearance. Thistle One Coat can be bought in sensible size bags, and stores forever in plastic tubs. For patches rather than chases I have always applied a cement/lime or latterly an NHL render base coat (or two) first. I have been known to prime the chase with dilute PVA first if I think it would help form a bond to the old plaster, and otherwise would wet the area first.

2/ I'm in the same boat, and I havent removed any of the cement renders unless there was an obvious problem. There was definitely a problem with an old chimney breast in my basement, that had been 'tanked' with a patent cement slurry and cement render, and the render there was hell to get off, and will be hard work to put back on in with NHL render. One or two bits of beautifully plastered cement render weren't straight enough to my eye, so they got straightened up too.

 

[Milfry]

I would be more concerned with the lower levels, previous owners had the damp wally in and have gypsum over the lower 1m of a lot of rooms and most of it is blown.
I am re-doing this in lime as I work my way around the rooms. BUT my first concern has been to solve the source and had blocked drains (solved), leaking gutters (solved) and high ground levels (partly solved).

You may not need to replace 100% of the gypsum, depends on how bad they are as well as money, time and future disruption.

Cheers,
Richard B.

Thank You for the reply. I have only owned the property a month, for which it pretty mush hasn't rained and I have birds nesting in the eaves which has stopped be getting up to the gutters but I plan to check everything youve mentioned asap. To be honest the area is question do not seem too damp, the paint has peeled slightly but I am unsure if this could be condensation/lack of ventilation as the previous owners blocked every single vent and hole possible to save on heating so I have lots of mould where furniture has been in other rooms etc. Thinking it might be better to leave over winter and assess everything a bit more before I start the destruction.

 

[Milfry]

1/ Plaster of Paris is just a finely divided gypsum plaster. Polyfilla is silica with a cellulose base, and although I'm not at all sure what that means, I only ever use it as a fine surface filler. Gypsum plasters have issues, but I'm dubious that a lack of 'breathability' is one of them. Gypsum plasters really don't like damp though, particularly where there are salts. Nevertheless I have used Thistle One Coat for filling the many chases above ground in my 1879 stone house and all of those have been absolutely fine after 25 years. This has been true even where the neighbouring original lime plasters had already blown slightly. Thistle One Coat is more open textured than pink finishing plaster, it doesn't polish so easily and the pros aren't keen on it for that reason. For older houses open texture is good and it's a good match for the lime plaster in appearance. Thistle One Coat can be bought in sensible size bags, and stores forever in plastic tubs. For patches rather than chases I have always applied a cement/lime or latterly an NHL render base coat (or two) first. I have been known to prime the chase with dilute PVA first if I think it would help form a bond to the old plaster, and otherwise would wet the area first.

2/ I'm in the same boat, and I havent removed any of the cement renders unless there was an obvious problem. There was definitely a problem with an old chimney breast in my basement, that had been 'tanked' with a patent cement slurry and cement render, and the render there was hell to get off, and will be hard work to put back on in with NHL render. One or two bits of beautifully plastered cement render weren't straight enough to my eye, so they got straightened up too.

Thanks for the reply and the advice on the one coat, looks to be a good compromise

 

[Stevers]

My house had been empty for 18 months up to December 1996, and when surveyed, even the shutters on the downstairs front windows were very damp. Not surprisingly really, living in a stone house without heat can be a lot like living in a cave - so lovely during the summer! We also had some drainage issues and a fair few blocked vents through dust, soil and/or cobwebs. One part of the downstairs floor had become completely unvented and that was the source of a definite damp smell under the stairs to the basement. When I put the missing vent in the smell went away overnight. With a stone house there is always a potential for condensation in the corners of outside walls, so careful management of any activities that might produce moisture is essential. When we moved in we fitted Passivents in the shower and bathrooms, and these vent out onto the roof via ducting though the walls. No electrickery required for these, as they open when they sense damp through differential movement of the materials used in the operating mechanism - sadly these clever little devices appear to be no longer available.

We also upgraded our gas central heating system using the Drayton Wiser system to give us better control of the temperature of each room through the day. With my mother now living with us and a son working from home, we have been able to heat a temporary bedroom downstairs at night and a bedroom upstairs during the day, whilst the necessary extra warmth follows my mother around the house. Since the heating is never fully off, just set lower in rooms not occupied, the house feels much more comfortable, and surprisingly gas usage over this winter has been in line with previous years.

 

[malcolm]

I've been filling in chasing for electrics recently. The plaster needs to be reasonably tough as it has to bridge the conduit. I'm using Ecomortar R50 which is breathable, fairly tough and sticks to most things http://www.anglialime.com/products/dry-ready-mix-mortars-renders-plasters/ecomortar-r50-2

It's no good as a finish coat for a small repair. One coat fills the chasing and then leave it just shy of the finished surface (or scrape a bit away after it's dry to get below the finished surface) and finish with a sandable filler. A drywall sander is very useful for getting the sandable filler flat to the wall.