How to render over damp course?

I am looking to render my old house, I have watched vedios on bunnings website and youtube. I tried my hand on couple of the wall inside the garage and was able to get the satisfactory finish. However outside the home is a different ball game. It has windows and damp course.

My question is

1. How you render over the damp course. I have a layer of brick which protuding a bit from the main wall, I am assuming its damp course layer. This layer of brick is atleast 15mm out from the main brick wall. Should i just render above this layer? what are my choices if i wish to render whole wall above damp course and below.

2. Most of the bunnings and youtube vedios shows the corner beads for windows but corner beads available in bunnning are with just 3.5mm Nib whereas most youtubers are using 10mm and also use this as marker of thickness of render. Can i use the 3.5mm nib and still render 10mm thickness,

Find more posts tagged with

Tools and Materials

Repairing

Renovation

Building and Construction

Decorating

Comments

R4addZ

Hi @CastleDiy

Ok so I'm no expert on this subject but I wouldn't bridge a damp proof course but if you must.... I remember installing an injected damp proof course in the UK and the cheat was that they rendered the wall with a render that had a waterproofing agent in it and rendered (IIRC) to a height of 1.2m because water can only rise 1m in brick before it's own weight forces it out of the bottom of the wall.

MitchellMc

Hi @CastleDiy,

That seems like a very high dampcourse line. Typically, they would be a couple of courses from the ground, not eight courses high.

If it is a dampcourse line, you could extend it through the render. That way, the top and bottom rendered portions would be isolated from each other, and no moisture could be transferred up the rendered surface.

You could just render the top portion if that's a look you wouldn't mind.

10mm render is quite thick and was something we did regularly in the past. These days, with improvements in technology, a 10mm thick render coat is not required. Renders such as Dunlop 20kg Multipurpose Acrylic Render can be applied with as little as 2mm up to 10mm. So, if you were to go with a product like this, the 3.5mm nib render bead would be perfect. I wouldn't suggest you try to apply 10mm of render over a 3.5mm nib bead, as you won't end up with a very robust corner, which will be susceptible to damage.

Please let me know if you have any questions.

Mitchell

CastleDiy

https://www.workshop.bunnings.com.au/discussion/comment/41609#Comment_41609

Thanks @R4addZ , @MitchellMc

I was considering a thick render because the brick layer just below the damp course is protruding about 15mm from the main wall. My initial plan was to render up to the level of the protruding brick to make the entire wall flush. However, I realized that a 15mm thick render would be difficult to manage and would likely require two layers of rendering. Should I render that one brick course at a different height than the main wall and treat it as a separate portion?

Also, is there a PVC bead that can work as a separator and potentially act as a damp barrier between the render above and below the protruding brick layer?

R4addZ

https://www.workshop.bunnings.com.au/discussion/comment/82933#Comment_82933

Hi @CastleDiy,

That row of bricks is just a decorative feature known as a corbelled row of bricks and has nothing to do with your DPC. I had just assumed the house was built on a slope and that was at the low end.

bruzzz

https://www.workshop.bunnings.com.au/discussion/comment/41609#Comment_41609

Hi,

We recently purchased a house and the DPC has been bridged by the render on the exterior walls. This was brought up in the B&P inspection as a potential issue as the moisture is being trapped between the walls and render.

Is there a way to fix this? Maybe cut a straight line through the render underneath the weep holes with a circular saw? Any suggestions? Thanks!

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/87878#Comment_87878

Hi @bruzzz,

It sounds like you’re on the right track—bridging the damp-proof course (DPC) with render can definitely lead to moisture issues. Decoupling the render by cutting a clean line just below the weep holes may help, but because this involves the integrity of your building’s moisture barrier, it’s really important to get advice from a licensed builder. They'll be able to assess the issue properly and ensure any fix complies with current building codes.

Please let me know if you have any questions.

Mitchell

Ivymantled

https://www.workshop.bunnings.com.au/discussion/comment/106299#Comment_106299

I'm having a 1950's brick house rendered and our plasterer insists the corbelled row is the DPC too - even though it's a couple of feet above ground level.

I don't see anywhere obvious below that where a DPC could be - no breaks, lines, or color variations in any of the bricks below it. I wonder if there was some trend in the old days to combine the corbell with the DPC.

JacobZ

https://www.workshop.bunnings.com.au/discussion/comment/122760#Comment_122760

Hi @Ivymantled,

Welcome to the Bunnings Workshop community, it is wonderful to have you with us.

It certainly seems like a pattern is emerging that would indicate it could have been a technique used back in the day. Do you know roughly how old your house is? It would be interesting to look into.

Did your plasterer mention anything about how they would address the raised DPC? I'd be trying to pick their brain to see what knowledge they have of this manner of construction, because I can't say I've ever come across it.

It certainly has me intrigued though. I always love an opportunity for learning.

Jacob

Ivymantled

https://www.workshop.bunnings.com.au/discussion/comment/130572#Comment_130572

Hi,

The house was built in 1951, in North Epping, Sydney.

As far as rendering below the DPC, there are two methods being discussed with the renderer:

1. Installing a Drip Bead 10mm above the DPC.

Drip beads are different to stop beads, which are the kind used at the edges of walls, and around window frames, door frames etc. when rendering.

They're designed to stop any moisture rising up, instead turning it back downwards.

There are various designs. Below is a diagram of how they sit, and a photo of the bead running along the side of a house.

2. Below-DPC rendering waterproofing additive

Mixing an additive into the render that is applied below the DPC, for protection along that band which runs along the base of the house. There are some products that waterproof, salt-proof and plasticise sand/cement renders. So the render doesn't suck up moisture or salts, and is supposedly easier to work with.

Cheers

JacobZ

https://www.workshop.bunnings.com.au/discussion/comment/135403#Comment_135403

Hi @Ivymantled,

I just googled "Sydney Red Brick" and found quite a few examples of houses and apartment blocks with this style where there is an obviously protruding row of bricks. It'd be brilliant if we could fine a brick layer who was around during this time to chat to. It's a bit of a niche topic that I'm not finding any real information on. It could just be an aesthetic thing, but I would love to understand the reasoning behind it.

Thank you for sharing the information that you have gotten from your plasterer, I hope that our other readers such as @CastleDiy might be able to use this info for their own projects.

Jacob

Child Item