A guy I used to work with had it installed in his 60s house, then came the problems. He removed a couple of random bricks himself and the rockwool was wringing wet. He’d been advised to use a waterseal product over the outside, but I pointed out that depending on how porous the joints/bricks were, he could be worse off because the water seal lines any holes, effectively converting them into tubes through the wall carrying water in even faster than plain soaking through. Many years ago I found that out the hard way using it above mum in-laws conservatory.
Cavity-walls that are already built up can NOT have cavity-wall insulation added. Cavity-wall insulation can ONLY be installed from the very start of construction of the cavity-wall. Cavity-walls must NOT be abridged with insulation(insulation touching the outer walls inside the cavity-wall), or else moisture will transmit from the damp outer wall, through the touching abridging insulation, and into the inner wall; making the inner wall damp inside the property. If cavity-wall insulation is to be used from the very start of construction , there must be a large air space gap in-between the face of the cavity-wall insulation panel and the outer wall inside the cavity-wall; this includes an air space gap in-between the face of the cavity-wall insulation panel and the cavity-wall tie drip-point(which must point downwards in the centre of the cavity). Cavity-wall insulation must touch ONLY the inner wall inside the cavity-wall of course. Ask City & Guilds N.V.Q. BRICKWORK teachers in person for PROOF of this.
Totally agree, but as a bricklayer in the 70,s ,80,s regs stated a minimum , maximum of 50/ 75 mm cavity, not great when your putting in 75 mm dry therm bats, , along with mortar snots not being scraped off internal blockwork,, causing mortar bridging and also damp transfer from brickwork to insulation which the HSBC lads never picked up on this but house owners are suffering now with this double whammy
It took hundreds of years to invent the cavity wall then only 50 plus years to decide to fill it. As long as I live in my 1960s house the cavity will never be filled. Yes I might save a bit of energy but I would rather have a house that can breathe.
Very interesting insight - surprised to see just how damp the thermal insulation was. Damp insulation is no insulation as heat easily conducts through the water and you end up with a cold damp house as you have clearly demonstrated. It does appear to be the case that retrofit cavity wall insulation should generally be avoided - other then perhaps poly beads in a sheltered location but only then subject to a satisfactory pre-installation survey by an independent and impartial surveyor.
Closed cell spray foam is the only option for cavity walls but good exterior paint or waterproofing for bricks needs to be upkept every couple of years
hi im subscribed to you and im in the same industry as you and totally agree with everything you say is spot on and you are truly one of the good guys in this industry do you have any videos or come across where the cavity has been filled with polystyrene beads that is causing damp so i can show a customer of mine who has installed yellow insulation that is wet and i have had advised her to remove it and open the vents back up but she wants to reinstall the polystyrene beads after please keep the videos up
Well done for also being a honest tradesman. I must admit that the beads aren’t as bad as the wall (pains me to say) but I have experienced wet beads that have caused issues and allowed water to penetrate inside. The beads themselves are waterproof but water can still be on them. That particular property was a block of flats about 40metres from the sea, but I didn’t get a video. If your clients wants to do that despite your advice, all I can say is that you were right to give advice and that is all you can do. A shame though.
@@CoastalWallTiesRustington hi many thanks for your reply that is what i say also the poly beads are better from the original install where they don't put an adhesive to make them solid the old method was install beads loosely allowing water if it does penetrate to filter through the gaps and drain away but the new method i have found is that some companies mix them with glue and in my opinion forms a trough for the water to hold
Yes, and the inconsistency of glue ratio is very common, which I put down to the glue line hardening throughout the day when going from one job to another, especially in the summer. Best bet leave the cavities alone as every type of retro fit cavity wall insulation does not cover all areas, leaving cold spots where lintels are and chimney breasts.
We have a 4-story block of flats with 50mm cavities and solid strong 100mm blocks, we have loose fiberglass insulation with voids, and we suffer from high heating bills E7 and mold. we have removed some outside blocks to inspect the fiberglass and have found it damp-wet, one company would do a clean-out and the new beads with an insurance-backed guarantee. We may just do 1 block out of 3 to see, or stick with internal insulation. This is our link. youtube.com/@riversideestate-jj2hr?si=oYhk0vFU77KVnJwv
Great video. But that is just the tip of the real problem. AS a builder, seen this for 30 years, now it will get worse with the need for insulation. Do we think the industry will fix the insulation materials?
My dear old dad always said that the cavity is there for a reason & should never be filled, it needs air to be able to circulate. Just think the wall ties could be corroding with the damp.
This is just like my property, seaward facing, 3-4 km, cavity filled with small grey polystyrene balls. Just how do I remove them? A vacuum cleaner? Thanks for the video, very informative.
What's the main cause of wet cavity wall insulation? It can obviously work most of the time so is it down to improper installation, bad materials, bad external conditions etc?
@@CoastalWallTiesRustingtonthanks for the reply. I've actually just bought a house that has ground floor damp issues. We've had a company come out and survey it and they've confirmed damp in several rooms plus a number of rotted floor joists but they weren't able to pinpoint the cause with 100% certainty. The house has had cavity wall insulation done in the past but there is no certificate available and the person who sold us the house wasn't the one to have it done (some previous owner and we don't know who it was). I think we're look at having it removed. Quick question: does it all need removing or only to a certain height? If you remove say 1-2m from ground level, won't the rest just drop down over time resulting in the same problem? Thanks :)
It's an expensive potential remedy, but what about water repellent coatings for the outer bricks? Like the Stormdry masonry cream, or rendering? residual moisture should come out via the dehumidifiers over time then they should be unnecessary presuming the rooms have enough ventilation (ideally MVHR). But if the cavity would struggle to "breath" then air bricks are an option that should allow air flow to the cavity once the majority of the face is water tight?
Stormdry is a great product but unfortunately it’s not 100% guaranteed to solve the problem due to having microscopic pores that make it breathable, this combined with wind driven rain can allow moisture through unfortunately. Having said that we think it’s great for preserving masonry in certain circumstances. I would never install air bricks directly feeding air into the cavity at low level, as this will allow the internal wall at low level to be a lot colder in winter months and if the occupants have a condensation problem, it certainly wouldn’t help matters, MVHR is good though.
We prefer to use a combination of manual extraction and vacuums as we can get a full view inside the cavity and remove any large bridging. The process is to remove a small cluster of bricks in strategic locations.
@@CoastalWallTiesRustington how long does an average house take you to clear and are you busy doing this work all the time, I’ve always had doubts about this stuff mainly it’s thermal properties as I’ve heard it all sinks down or has areas within the cavity where there are voids which is pointless.
It can vary greatly but for a complete house 3 decent sides, you would be looking at about 7 days but that depends on how many windows and doors there are and how much debris is blocking the cavity.
