# Forum Home Renovation Rendering  Render Crack Repair Options

## spartan

Hi Guys,
I've just purchased a new home - well its about 12 years old and is rendered brick.
The render has about half a dozen cracks in various places - most of which are about 1mm wide in various places.
Its a large two story/split level house - about 60 sq's internally.
The biggest of the cracks is about 4m long from ground level to the roof eaves.
The building report certainly mentioned them and said that they were normal for a building of its size/age etc.
I spoke to the building inspector and he said that it was pretty typical for render of that age, and mostly likely due to settling and expansion/contractor around some of the windows etc. 
Assuming this relatively benign cause.
What I'd like to know is it possible to repair these kind of cracks to make to it look they were never there? 
Regards

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## mainly-outside

Hi Spartan,
there are two types of cracks in Render, one is crazing or spider web cracks and the other is structural. 
You can see crazing when you wet unpainted render as it comes about from surface tension as the MPA increases or from shrinkage due to a poor preparation of the mix. Usually it is random and not subject to movement however it can allow water ingress and as water ingress increases it it gives the perfect environment for efflorescence or growth which can make the situation worse. This mainly happens in site mixed render not so common in major brand pre bagged renders 
 The structural cracks will usually follow the underlying substrate moving, either by following the bricks (step cracking) of if the renederers rendered over an existing control joint which will result in a straight line, in this circumstance it is fair enough to say the render doesn't just crack, its whats underneath. 
sounds like you have the later;
to fix it simply grind out the render to reveal the control joint underneath,(make sure you clean all the render out or it will crack either side of the join as it is easier to crack the render either side that crush the thicker render in the join) sometimes its just a straight line in the mortar. Once all th render is cleaned out put backer rod in it mask each side and use a good polyurethane sealant to fill the cut and allow expansion and contraction. Remember that polyurethane (sikka) isn't UV stable so it will need painting and inspection every couple of years because as the paint breaks down it will expose the polyurethane to UV. 
Sort of a side note, paints that are simply designed for exterior are never going to protect a rendered house which as you could imagine is very porous, even if it said suitable for render on the can. sure it will stick but you need an impact or an elastomeric membrane as they are crack bridging, anti fungal and protect from water ingress. Go to a specialised trade centre that specialises in exterior coatings, but 4mm need repair not just paint.
Cheers 
Chris

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## spartan

Hi Chris, thanks very much for the response.
Taking the sikkaflex approach - would it not be obvious where the crack was? I.e., obvious that's not render?
The biggest crack (in terms of length) is next to expansion joint in the render - about 300mm to the left of it actually.
Other than this one - the others are in the vicinity of windows - just above or just below..and have the slight step pattern of the underlying bricks.
Cheers
Warren

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## mainly-outside

Hi Warren,
Your right, the sikka approach would definitely show a difference in comparison to render, it should only be done on a completely straight line or where an intended Control joint is. Sounds like you have step cracking around the windows which is pretty normal as the weakest point is around the openings, I would suggest giving your wall a chemical wash ( 30 second cleaner or similar) and hitting it with a membrane paint that will achieve at least a 180 micron dry film build, as this will crack bridge and remain elastomeric for a good 6-7 years with a good paint such as RSA Rendbrane, I can point you in the right direction with that if you like, depending on where you live?
Is your house built out of besser blocks? Could the crack be 400mm ( the width of a block) away from the control joint? Are you in a duplex that has a party wall?
The reason I ask is it sounds like the original contractors may have missed the joint all together. No biggie it is still repairable quite easily.
If you are really keen post a photo and I should be able to help a bit more. 
Regards Chris

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## spartan

Hi Chris, 
House is located @ Albany Creek. My contract doesnt settle on the house until 10 Sep. The cracks are one of the few things that are 'wrong' with the place and I want to get them sorted first up so I can concentrate on creating sawdust in my workshop  :Smilie: .
I have attached two photos. These are of the long crack.
It is vertical and unlike my suggestion in the initial post it appears to be between 10-40mm from the expansion joint (not 300mm). The width of this crack consistent with the others (about 4 others) around the house (mostly 1mm - but 2mm at some points).
From memory I think there might be a couple of small ones that have had the sikka treatment.
The bricks are standard size, and no it doesnt share a wall with any other home or property,
The other racks as indicated are near windows and have more of a stepped shape.
Note the 100mm pipe in the second photo is horizontal and takes rainwater to the water tank.     
Regards
Warren

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## mainly-outside

Hi Warren,
thanks for posting that pic mate. The joint looks like it is most likely cut exactly where the joint is however it simply isn't cut deep enough which  isn't  allowing articulation. The problem is that when renderers render a wall they spread the wet material over what could be a 10mm control joint and then come back usually the next day then use a semi disk (which is a large masonry blade that has been snapped in half) they score the dry render usually along a straight edge. Some time the bricklayers don't make the control joint straight and if the renderer was to follow the actual joint it would look untidy. In each case the render is usually thicker in the joint that it is thick on the adjoining wall and as you could imagine, it would be easier to crack 3.5mm of render on the main wall than crush 10mm x 10mm of render in the joint even with a 4mm scored line on top or near  it, this is what has happened on your house.
It really is the responsibility of the Sold Plastering contractor to manage their control joints however if it was done 10 years ago it is out of his QBSA licensing obligations. 
So from there I would do the following;
You need to assess any drummy render by running something metallic over the cracks like the face of a hammer, but don't tap it just lightly run it over the surface it will sound hollow if it is drummy.
If there is anything drummy you will need to remove it by cutting it out with a grinder, if you decide to bash it out you could chase the drummy render over a larger area.
If the render is not drummy you can grout the cracks with Flexirender to fill them in.
You then need to find where the control joint is at the top and the bottom, ping a chalk line and then cut the render all the way through. Patch the render if any  drummy was removed ( I would recommend a contractor as even the best patch in the world can still look like a patch), mask either side of the joint , sikka it remove the masking then repaint the area with a good elastomeric membrane like RSA Rendbrane.
I can assure you the joint will never craze either side again and the rendbrane will cover and travel with any minor step cracks around your windows.
Albany creek isn't to far away from Geebung where you can get the RSA (Render Systems Australia) material including the chemical wash, flexirender, polyurethane sealant (sikka) and Rendbrane tinted in any colour any brand.
Alternatively if your on the Sunshine Coast you can go the the Externals Systems Centre its where I work and I would be happy to talk you through the process, we also stock everything there also. 
Hope it goes well.
Regards
Chris

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## spartan

Chris, thanks... 
So to summarise what you've said.
The issue with the control joint is that more than likely the render is thicker at the control joint than the wall next to it. Therefore the wall has cracked rather than the joint.
Overall - it doesnt appear to be a huge drama -
I need to check for drummy render - with any drummy render removed and patched. 
If there is no drummy render - I can get away with using the RSA compound to fill the cracks.
With the step joints I could get away with just the RSA compound and do this pretty easily myself? 
For the one control joint you recommend, finding the location of the actual joint, cutting through the render and putting in the sikka into the control joint. 
If I wanted a contractor to do all of this for me, is a major job (it seems straight forward if you know what you are doing). What kind of dollars would be a reasonable expectation(I guess assuming little or no drummy render)....Finally I am assuming I could achieve a result that looks like there were no cracks?
Would you recommend and particular contractor that would be familar with RSA range of products? 
Control joint/contractor bit aside - If I can do all the other bits myself - I'd quite happily take a trip the sunshine coast to pick up what I needed. 
cheers 
Warren

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## mainly-outside

> Chris, thanks... 
> So to summarise what you've said.
> The issue with the control joint is that more than likely the render is thicker at the control joint than the wall next to it. Therefore the wall has cracked rather than the joint. Correct Overall - it doesnt appear to be a huge drama -
> I need to check for drummy render - with any drummy render removed and patched. Yes or it will eventually just fall off or allow water ingress  If there is no drummy render - I can get away with using the RSA compound to fill the cracks.
> With the step joints I could get away with just the RSA compound and do this pretty easily myself? Yes you can easily do it yourself its just a matter of sponging it in  For the one control joint you recommend, finding the location of the actual joint, cutting through the render and putting in the sikka into the control joint. 
> If I wanted a contractor to do all of this for me, is a major job (it seems straight forward if you know what you are doing). What kind of dollars would be a reasonable expectation(I guess assuming little or no drummy render)....Finally I am assuming I could achieve a result that looks like there were no cracks?
> Would you recommend and particular contractor that would be familar with RSA range of products? You can acheive a result of no cracks easily DIY if there is no drummy render. As far as cost, it is a bit of a hard thing to calculate and for that reason most guys will charge hourly plus materials for that reason 
> Control joint/contractor bit aside - If I can do all the other bits myself - I'd quite happily take a trip the sunshine coast to pick up what I needed.  
> cheers 
> Warren

  Hi Warren, 
I have filled in some answers to your questions above.
I think if you have no drummy render and you have access to a grinder, I can easily walk you through the rest. If you want a contractor to do the patches and fill the control joints I can help you out with that also, I would be guessing it shouldn't take more than a day for one guy you might be looking at $400 at worst case scenario, could be as cheap as $100. 
If you want to come and see me I can supply all the gear and walk you through the process, my shed is at 13 Latcham Drive Caloundra West it is called the External Systems Centre. Ph - 54389282 
Cheers mate
Chris

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## spartan

Thanks Chris I will look you up in a couple of weeks.
I went and did the pre-settlement inspection today.
The owners had fixed a couple of the cracks, and painted over some of the others.
I noticed the control joints that I have taken the photo of are about the width of one grinder blade.
Interestingly I glanced over at the wall to the neighbours house, and noticed that they had massive cracks on the opposing wall.
It looked like a combination of cracking and popping of the render....be interesting to talk to the neighbour to see how long its been like that.
Each time I visited in the house I didnt look next door.
Probably about 10 metres away - I also noticed that there wall had not control joints at all!

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## mainly-outside

> I also noticed that there wall had not control joints at all!

  Can be pretty common, some walls like fire walls can sometimes be engineered not have them over spans greater than 6m. In saying that they are often on a zero boundary wall.
Good luck with the handover, see you soon.

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