Tips for knocking off plaster

anna.bloom

Hi

WE are having a damp proof course, put in on Wed and to save on costs, we have offered to take off the render down to the brick work, but how do you do this? is it had without damaging the bricks. Is it going to take a long time? any tips on how to do it?

Many thanks

keith969

Bolster and club hammer. How easy depends on how well attached the render is...

diable

How much needs removing as plaster can just fall off with a light tap or be bonded to the wall but the strongest stuff on earth (I exaggerate) it might be easier using a drill that has a chisel function, something cheap from Wickes would do. I am not sure but this one might be ok http://www.wickes.co.uk/710W-Percussion-Hammer-Drill/invt/195535

andy69_2

Did this myself about 2 months ago, just use a lump hammer and a bolster! Dont worry about the brick it wont get damaged, just put your back into it lol! Some bits will fall off without too much work!

David_Aldred

Hi Anna,
There are a couple of points worth mentioning here:

When you knock the plaster off for damp proof course work: Remove all plaster back to sound substrate (especially gypsum plaster) and any surface coatings. Rake out all exposed mortar joints at least 15mm to provide keyed surface.

The reason for raking out the mortar joints is because this is what is specified by the majority of the remedial damp proof course (dpc) manufacturer's and also the Building Research Establishment (BRE) when using cement based re-plastering systems due to the weight of the material having to hang upon the wall.

If there is a claim later you need to ensure that you did everything by the book otherwise those issuing the guarantee will blame you rather than the contractor. In fact to be honest I would have the contractor do everything including the hacking off even though this is at greater cost because it removes any split liability should there be a dispute at a later date.

The best way to remove plaster of any significant area is to hire or borrow from the contractor a mechanical chisel of a decent size often referred to as a Kango breaker rated at 110V for site safety and with appropriate transformer and leads. Hilti do an excellant range such as the TE505 or similar but the hire ship will advise as will the contractor.

Make sure you remove all timber grounds / wedges from the wall as these should not be buried within walls suffering dampness however caused otherwise they could propergate a dry rot. You need to have removed skirting, door architraves and plaster from between stairs and walls.

Of course you can use a hammer and bolster as indicated by others but this depends upon how long you want to take and how good your body joints are / you want them to be after you have done a few rooms. Whatever you use make sure you have appropriate personal protection - steel capped boots, gloves, ear defenders, goggles and appropriate graded breathing mask as a minimum.

Prior to starting remove anything that might be damaged by plaster dust or if it cannot be removed you need to suitably protect it - be mindful of floor finishes / electrical items etc. Use tape to seal off doors to rooms that are not being treated.

Be very careful whether using mechanical chisel or hand chisel about services buried within the plaster. Check where they run by metal detector etc before you start and tracing / marking upon wall before you commence - do not assume they all run vertical / horizontal because some idiots may have run them in any direction.

Have appropriate first aid on hand before you start - do not do this on your own so one person can watch the other in case you light yourself up with the mains or soem other accident occurs.

Think about any services you want to renew / change such as socket locations etc that should be done before the re-plastering and after you have removed the plaster.

Make sure the replacement dpc is actually justifed. Electrical damp meters cannot prove rising damp and the vast majority of the UK housing stock are built with a dpc such as slate or bitumen that does not disappear. If the house was built with a dpc chances are the true cause of the damp has been misdiagnosed as dpc failure from somebody selling a dpc / a surveyor who should have known better and as such the damp may well come back to haunt you at some later date for which the dpc contractor will deny is anything to do with them which is quite right since it will likely be nothing to do with the dpc in the first place.

Any work to the party wall including a new dpc comes under the Party Wall Act.

Not an exhaustive list but hope this helps - kindest regards David Aldred Independent damp and timber surveyor.

dampdaveski

tut tut David,
'Make sure the replacement dpc is actually justifed. Electrical damp meters cannot prove rising damp and the vast majority of the UK housing stock are built with a dpc such as slate or bitumen that does not disappear. If the house was built with a dpc chances are the true cause of the damp has been misdiagnosed as dpc failure from somebody selling a dpc / a surveyor who should have known better and as such the damp may well come back to haunt you at some later date for which the dpc contractor will deny is anything to do with them which is quite right since it will likely be nothing to do with the dpc in the first place.'

Bitumen can crack due to historical movement, and fail over time (as bitumen roof can) and slate is indeed impervious to moisture, but the mortar bed it's laid in isn't!

Using your parameters 'chances are' that all independant 'damp' surveyors are bigotted, self rightous zealots

Borrow a breaker from the contractor? Surely you would advise the customer to provide risk assessments and method statements to the contractor and to make sure they have insurance in place in case they break it OR hurt themselves??

I hope you have handrails and toe boards fixed to that very high pedastel you're stood on
Merry Christmas and a Happy New Year to all :xmassmile (including you Dave:beer:)

David_Aldred

Hi Dave,
All the best to you and your family for 2010 - electrical damp meters cannot prove rising damp as clearly stated within BS6576 that is not an opinion that is a fact. As you are a contractor selling dpc's we are hardly likely to agree on whether a new dpc is justified to a property suffering dampness but we do agree on helping people with their queries on here as best we might. As you know I only suggest new dpc's are installed where rising damp is proven to exist and where it is proven to be so to habitable accomodation I have no hesitation in proposing to clients such a problem be addressed.

A bitumen dpc can crack with significant settlement of a house but the amount of dampness that would emerge up through such cracks does not correlate with the full wall lengths of dampness apparent or recommended by the contractor.

As with anything if you haven't proved it is occurring you are simply guessing and a guess from somebody selling a product to install that product for their own profit may not be the most appropriate approach to investigation.

Kindest regards as always, David Aldred Independent dampness and timber surveyor.

Tucker

I'm confused.

Is it external render or internal plaster we are talking about removing here?

David_Aldred

Hi Tucker,
Sorry for the confusion it is internal plaster under discussion in this instance but there are various specifications for such and whilst older housing stock often was constructed with traditional lime based plasters that may be relatively easy to remove, especially when degrading; the house may have had plasters in some area that are far more difficult to remove such as those which use a base coat of sand and cement.

In addition some plasters used with replacement damp proof course work are of a hard dense sand / cement type that are relatively heavy compared with traditional lime plasters and hence the need for them to hang onto raked out mortar beds rather than relying on simple adhesion to the substrate. Hope this helps, kindest regards, David Aldred Independent damp and timber surveyor

keystone

David_Aldred wrote: »

a mechanical chisel of a decent size often referred to as a Kango breaker rated at 110V for site safety and with appropriate transformer and leads. Hilti do an excellant range such as the TE505 or similar but the hire ship will advise as will the contractor.

I would have thought a Kango would be a bit OTT for this job - its not concrete being broken. Why would an SDS drill with a chisel function not be adequate especially as Mr and Mrs Average might find using a Kango horizontally a bit stressful on the old back? They'll also have a lot more control.

Might I ask why would you recommend 110v in a doemstic environment seeing as the only cables likely to get chopped are those inadequately installed / routed behind the plaster you are removing and thus at 230V anyway?

Cheers

andy69_2

Could I just say I did mine last month and all i did was knock the plaster off with a bolster, and then drilled the holes, then the guy came in and injected, plasterer came and plastered up to the holes, scirting over the holes and allow it to breathe better, is this not ok? No damp since!