Wall rendering

starM

Hi,



I need some advise please. My house is around 100 yrs old. Some of the bricks are deteriorating and we're getting a bit of damp through the walls as they're slightly porous.


I was considering rendering and trolean finish to be applied. Some has suggested K rend.



Which one would be better for longer period of there is anything else you can suggest?


Thanks

tacpot12

Well, K Rend is a company that makes lots of different rendering products, and Tyrolean is more of a method of application for cement rendering, so you do need to research whether rendering is a good option, and if so which product is best.

There are other options to consider:

If the bricks are not too deteriorated, a breathable but waterproof solution can be applied to the bricks.
The bricks can be repaired by either removing them and replacing with new. This is a job for a specialist bricklayer.
The bricks can be repaired using this system: https://www.plastic-surgeon.co.uk/article/brick-repair/

One issue with rendering is that it binds to the bricks really well. When the render eventually fails, it will pull out more of the loose surface of the brick, further increasing the risk of structural failure. I would suggest you need the services of a chartered surveyor to advise on an appropriate method of repair.

ceredigion

https://www.netweber.co.uk/renders-decorative-finishes.html

FreeBear

starM wrote: »

I need some advice please. My house is around 100 yrs old. Some of the bricks are deteriorating and we're getting a bit of damp through the walls as they're slightly porous.

I was considering rendering and trolean finish to be applied. Some has suggested K rend.

At 100 years old, I'm guessing you have solid brick walls ?
A few properties around that age would have had cavity walls, but they are few and far between.

With solid brick walls, the last thing you want to be doing is slapping a layer of waterproof cement or K-rend on the outside. Neither are breathable, nor suitable for solid walls.. And before anyone passes comment on that, K-rend is a silicone based resin coating system that is only slightly more breathable than cement.

For solid walls, lime render is the best solution - It is breathable, flexible, and has a degree of self healing when micro cracks start to form. Being breathable is vitally important in preventing moisture building up in the bricks and migrating through to the inside of the building. The downside is there are few craftsmen willing to work with lime, and the few that do, charge a premium. Material cost wise, lime render should work out comparable to K-rend or cheaper.

Note - Lime render does not contain cement. Many builders will add hydrated lime to a cement render to improve spreadability, and consequently be tempted to call it "lime render".

If you need further advice on the subject, have a chat with someone like Mike Wye or Ty-Mawr.

Furts

My take is a little different. There are millions of 1920-1930 homes still standing with cement render, so it stands the test of time and it works. I accept some of these will have cracks some will need painting but materials deteriorate with time, homes move, damage occurs, alterations are done and so on. The problem with much render done in recent decades is it is not done properly. Cement based render is a 2-3 coat system depending on location, and with a deliberate weakening of layers to allow for movement. If the principles are followed with the right mix, the right sand, the correct cement, and the right finish then it ticks a box.

maisie_cat

I thought that old houses should have lime render so that the solid walls breath, my 1936 house certainly has. Any paint also need to be breathable. The only damp I've had in my house as due to plastic paint, which created an effect like wrapping the house in clingfilm. When it develped micro cracks over time water got in and couldn't get out. We had to strip off so the house could breathe again.
check heritage homes before you install anything http://heritage-house.org

Furts

maisie_cat wrote: »

I thought that old houses should have lime render so that the solid walls breath, my 1936 house certainly has. Any paint also need to be breathable. The only damp I've had in my house as due to plastic paint, which created an effect like wrapping the house in clingfilm. When it develped micro cracks over time water got in and couldn't get out. We had to strip off so the house could breathe again.
check heritage homes before you install anything http://heritage-house.org

On old timber frames one uses lime, but brick houses circa 1920 -30s had render that was roughcast, or pebble dashed, or painted with paints mixed up on site. They all breathed and worked - there were no plastic coatings then stopping breathing.


But people can have strange ideas about breathing. My house bricks and the mortar do this naturally - as do other bricks on millions of homes. It is all a matter of what type of brick is used to build with. Typical 1920-30s houses used cheap London bricks and these are very porous.


Your house is 1936, OP's home is 100 years old, and these are not heritage homes. They are mass produced, or volume designed, low cost, simple construction much like today.

FreeBear

Furts wrote: »

On old timber frames one uses lime, but brick houses circa 1920 -30s had render that was roughcast, or pebble dashed, or painted with paints mixed up on site. They all breathed and worked - there were no plastic coatings then stopping breathing.

By the 1920s, cavity wall construction was becoming common place. My house, being on the cusp of the change over, has cavity walls on the ground floor, and double thickness solid brick on the upper. Just the upper half is rendered with cement & pebble dash finish. The lower half is a very soft local facing brick.

Internally, the walls are lime plaster which mitigates some of the issues that the cement render may cause. Although, being in a sheltered location with fairly low rainfall, penetrating damp isn't a major issue.

If the property is of cavity wall construction or SIP & brick skin, then sure, use cement or resin based renders - The cavity will provide the necessary isolation to prevent moisture from going right through the wall. But... If the facing bricks are soft like mine, a lime render is preferable.

Furts

FreeBear wrote: »

By the 1920s, cavity wall construction was becoming common place. My house, being on the cusp of the change over, has cavity walls on the ground floor, and double thickness solid brick on the upper. Just the upper half is rendered with cement & pebble dash finish. The lower half is a very soft local facing brick.

Internally, the walls are lime plaster which mitigates some of the issues that the cement render may cause. Although, being in a sheltered location with fairly low rainfall, penetrating damp isn't a major issue.

If the property is of cavity wall construction or SIP & brick skin, then sure, use cement or resin based renders - The cavity will provide the necessary isolation to prevent moisture from going right through the wall. But... If the facing bricks are soft like mine, a lime render is preferable.

Fine, but gypsum plaster breathes. So it does not have to be lime used here. If the plaster is coated with vinyl paint then the concept of breathing immediately takes a hit. Since emulsion paint has varying amounts of vinyl this situation applies to almost every house. Which means the plaster is not the decider on breathing, it is the paint coating put on it.