Gypsum vs Lime - The Rennovation Couple - DampSam Reacts 

Cheaper modern methods that I'm hacking off everyday because they get wet through. So many times I've ripped off gypsum on old houses but the old bricks and mortar are dry. All the time Sam. It's not progress. Old houses need old methods. Put new material on a house built in 1616 and you will get damp issues. Every time. I'm filling skips up daily mate.

FYI ‘Breathability is the water vapour transmission rate, or the speed at which vapour passes through a particular material or construction.’ I’m surprised them didn’t cover this on your CSRT course.

So to clarify - if I’ve removed a load of blown lime plaster from the interior of an external wall, I can slap a load of multi finish on in its place with no ill effects? Is it just “big lime” lobbying Historic England & all our conservation officers to sell the “if you have solid walls, plaster must be breathable, and therefore must be lime” party line?

I’m a North American builder who studied vapour barriers and air tight building methods and also have experience on historical buildings . Now living in Ireland and restoring century old house with extra 1970 addition on it .(very similar to U.K building practices and environment) In N.A We have been using poly vapour barriers since late 1970s and insulation on interior and is probably one of the best improvements for heat and condensation. We started using mechanical ventilation since 2000’s and is now good building practice in N.A , modern well built houses had air quality tested to be the best . Moisture and toxic vapours from carpet/glues are exhausted and replaced with exterior fresh air . These building details have been designed by building engineers , Architects and extensive case studies since early 1970’s. Old section I’m exposing interior stone/brick surface . I ripped out all the interior cladding consisting of layers of crumbling lime plaster , oil paint , insulative wall paper , 1/8” wood paneling, painted and then wall papered again . All these layers were damp and disgusting . Then I reversed the exterior grade/slope to shed water , replace black soil with perforated drainage pipe to sunlight away from house and graded in crusher run . Fixed rain drainage to storm/sewer . Replaced interior old concrete slab with damp proof/radon, 100 mm insulation and concrete. I noticed the dampness 3’ up the stone walls disappear in a month . The stone house is nice and dry now and I’ve done nothing to the walls “yet “ The outside has cement render in excellent condition apart from a few subsidence crack which I’ll leave as a “ settled condition” . If I put gypsum on interior old stone walls it’ll probably fall off where as lime plaster would allow the water moisture to pass to inside and hopefully get pushed back out windows with heat and or ventilation. Mould occurred from lack of air movement and probably feeds of the interior dust and excessive humidity which can grow to alarming levels if not checked . In 1970 section of house I will use gypsum board on 3” insulation on interior but insulation will stop any external moisture damaging the slab (hopefully)

You take the word breathing to literally, come on it is the perfect word to describe the process with lime.

You can plaster hemp lime plaster on at 40mm if you want because it won't slump and it will carbonate

If you want to put modern stuff on old walls then your going to have to change the bedding mortar, especially if it's common earth mortar because that will hold on to water until it sinks and the stones start fall because there's no bedding left. If you don't understand lime or earth mortar then your methods are actually the dearest around because they will keep failing.

Also id bet any money lime and sand is cheaper than whatever your using . The client if often happy to pay a little more for the correct job. If you took your tyres to be changed you pay more for decent ones because they last, not save a few quid and get crap ones that wear out.

Guy has his head full of sawdust and pound signs in his eyes.

When they say "breathe", they mean that the plaster & mortar is very permeable to water. This is a good thing in old houses. Of course gypsum is permeable too, just not as much.

If anyone knows the term interstitial condensation they should know how to work with solid walls.

Diathonite is a really good solution to damp and condensation issues, really good insulation lime based. But like anything lime it’s a bit more money than gypsum. Modern plasters are fine if installed correctly.

Hi Sam 18 years time served plasterer here. Now on previous videos ive seem you appealing for plasterers to become qualified. What qualifications are best to go for? Ive looked online and theres so so many

"letting a building breath" I guess is a modern term, maybe miss understood by some not doing the correct research. However as a home owner of a 1800's terrace house, with damp, all this term means to me (and I hope a lot of others) is better ventilation...or indeed help the building move any moisture

The trouble with Gypsum when the house becomes airtight and well insulated Gypsum supports mould growth, Lime is too Alkaline to support mould, but I do agree Gypsum does pass vapour/moisture and so does cement render unless it has waterproof additive put in in.

All old property used to breathe because off all the gaps in the windows and doors. So now with all the properties now having to be air tight this is now the problem.

Hi, thanks for the video. It's really important point as I have an Edwardian property that needs replastering and getting quite worried about what to use. Out of interest, is your opinion that the insulation is causing the condensation problem, and that the plastering doesn't have an effect? I read that it's the internal insulation that makes old building vulnerable to condensation and water build up. Also, in my Edwardian property, the lime plaster that's been there since the previous owners is crumbling off. There's something black it's sitting on though - do you know what that might be?

When people talk about houses breathing, they are really talking about the vapour permeability of the walls and finishes. I initially got hoodwinked into thinking gypsum plaster was not permeable listening to all 'breathable' plaster and paint manufactuters, but as you say, they are telling a lie to sell their products. I do believe that modern paints (dulux emulsion) are not vapour permeable and you need to find paints that are - if painting over a solid brick or stone walls. External cement render and cement pointing over lime mortar are a big killer for walls and should be removed.

Can you polyurethane a tile backer board to a damp wall and skim with plaster?

Stop saying vapour passes through materials. Open pored line mortar acts as a poultice. Water as a gas can not pass through open pores. Your thinking of water as a liquid after condensation takes place.

Another thing for DIY people Gypsum products reduce scope for creativity ie: rounded corners, they set far too fast and do not give the DIYer much time.

Lime plaster with distemper paint allows moisture to pass out of the wall more easily than gypsum with a modern eggshell. Are you trying to say the difference is negligible? Its not

Is SBR latex Permeable Sam, what about bitumen, and the PVA you use to bond the skim to the substructure of historic buildings... and the chemicals that are being injected into thousands of historic buildings right now due to bad advice. I think you should do a course with SPAB and get an upgrade mate, stop selling your snake oil to unwary punters.

How does Vinyl wallpaper deal with damp? Like not using gypsum, I've heard vinyl wallpaper is also a no no. Is this another lie?

Aaah mate, you are so wrong... I fix these problems all the time with successfull results. You need to stop talking shit to people

Sam on your 5 tips to prevent black mould book tips 2 and 3 are the same ❤

If you put tanking systems and membranes on solid stone walls you will literally trap moisture in the wall Now on a period property you could have perfectly good wooden lintels that have lasted 100s of years But as soon as you throw on non permeable products on walls (that are naturally beathable/permeable) you will begin the cause dry rot and potentially damage softer masonary. You literally contradict yourself in your videos and in your trade Maybe you hide damp problems on certain buildings but give it a few years and it will be back Cement on solid walls causes cold spots=condensation Tanking is made from cementeous material Plastic Membranes (put it this way if you put a wet sponge in a plastic bag the sponge is still wet maybe you cant see it but whats all that moisture doing within your walls its softening the foundations) I spend half my time removing shite damp proofing systems because it has caused a different type of damp. I worked for a well known damp proofing company and it disnt take long to realise damp proofers just thoughtlessly and temporarily hide symptoms of damp. With all due respect ive seen a few of your videos and some are alright but mostly your just making up explainations to suit your knowledge In a very close minded way

Staff beads.

@dampsam do a follow up video on the jobs you have done and shared on RU-vid a year or two later…that would proof your points. Commenting on someone else’s video doesn’t proof your points. BTW, certain paints are not permeable. Gypsum is but the issue with it is that mould grows on gypsum but not on lime due to its high ph level.

This guy has zero knowledge about building science. An absolute grifter.

Cut youre plasterboard stick it on with the megastick foam take youre lime mix it in a large glass of gin sit back and breathe and think of the money and hard graft you have saved

All looks bone dry Seems like a waste of their time money and effort that Bagged modern renovation plaster does the same job as lime Hence the name

bit pedantic about semantics really - I don't think anyone is genuinely under any impression a house has lungs lmao

Your about about EPC is bang on. Well until you said storm dry. Stor.m dry is a disaster and will again make sure the bedding material will suffer