Victorian Solid Brick Wall + Render...

[jungle_jim01]

Ok...here's one for discussion! I'm steadily renovating my property...starting with the outside and workin in! The Front of the house is a 2 storey victorian brick extension with solid walls (i think) approx 250mm thick. It's been rendered in an ugly lumpy render which i presume is cement based. The render isn't in great condition with a few cracks. Presumably the ideal would be to pull off all of the render and replace with a lime render? Does anyone have any experience of this, advice, or idea of costs?

My dilema is that this is my first house and very much a 'stepping stone' to bigger projects in a couple of years time. I want to do a good job but without getting carried away financially. Is it feasible to repair and skim the current render??

I'd really welcome thoughts and suggestions.

Cheers

 

[Feltwell]

Is the render starting to part company with wall beneath?

Aside from breathability, if it is coming away then you definitely don't want to put anything on the top as that will only be stuck to the loose stuff. My limited experience with external render has been if it's starting to come loose in 1 area, chances are once you start taking that off you'll find the rest of it comes away as well. On my previous houses patch repair wasn't really an option, as soon as I started taking some away it quickly became apparent that the whole lot was loose and had to come off.

 

[AMc]

My dilema is that this is my first house and very much a 'stepping stone' to bigger projects in a couple of years time. I want to do a good job but without getting carried away financially. Is it feasible to repair and skim the current render??

Some bodger developers would patch the cracks then apply a coat of masonry paint just before they sold - if the house is dry that might not be the end of the world for the house, but if the render is blown or the house is damp then it would literally just be covering up the cracks.

If you're not planning on being there long term then I would think carefully before you start hacking away what's there. I haven't done it but understand that removal is time consuming, hard work. Rendering in lime is going to either require an investment in training and time or in a specialist company to do it for you. If the render isn't in bad condition and the interior isn't suffering from damp then it might not be the best place to spend your time and money - I doubt you'd see a 'return on investment' even if the house is damp as most surveys seem to recommend a pointless silicone treatment - even if they do recommend re-rendering in lime a quote and adjustment in the selling price can be as useful in securing a sale as doing the work. At that point you're missing profit on the house, but you're not spending the money up front and hoping to make it back at the end having paid interest on it in the meantime.

If the house is suffering from damp then it's probably the best thing to do, likewise if this is a long term home but have think before you start down that road - act in haste, repent at leisure and all that. Whatever you do try not to make it worse for the next person and the house itself.

 

[Penners]

As Feltwell and AMc have pointed out, the critical question is this: is the house damp?

Removing a concrete render (or - as you describe it as being lumps - possible pebbledash) from a brick substrate is not to be undertaken lightly. It may prove to be simple, and fall away from the brickwork easily. But there's also every chance that areas of it, at the very least, will be firmly adhered to the bricks. Removing this can be time-consuming and, unless you're extremely careful, damaging to the bricks.

If you believe the exterior walls to be damp, then perhaps you should try removing a smallish area of the concrete, to see how you get on. If you're very lucky and it falls away easily, then - with your fingers firmly crossed - you may decide to press on. But if it looks as though a considerable proportion of the concrete is stuck fast to the bricks, then it's worth considering whether you might be better to remove any damp plaster from the inside walls, and leave them to dry out that way. make sure you repair all cracks in the exterior render first, otherwise the water can continue to penetrate and undo your good work.

But, to come back to square one, the critical question is whether the walls are damp.

 

[chuckey]

Do a sketch of the wall, then mount your ladder and whack the render with th HANDLE of a hammer, the difference in sound between stuck render and loose render is substantial, mark your result on your sketch. Move your ladder and repeat. . . . When you have biceps like Popeye, examine your sketch and make a decision.
Frank

 

[EricD]

thats a great idea, and least then you can see on where it actully is rather than on a sketch

 

[Merlin]

I am in the process of removing the bottom metre of cement render from the kitchen wall at the back of the house. The bottom 30cm is very wet and dropped off without much effort, but as I get higher then the render is more firmly stuck.

I am not planning on re-rendering, but repointing as the only reason the render is there is that the previous owner couldn't be bothered with repointing, so just slapped render over the walls.

I am using a hammer and large screwdriver to get behind the render. A brick chisel would be too vicious and risks damaging the bricks. Once the render is removed I brush the bricks with a steel brush and they look in good condition. (The pointing is not in that bad a condition either!)

It is a laborious task though and I only do a couple of hours at a time in between decorating indoors. There is no way I could get the motivation to do the whole lot at once. I started small, accepted progress would be slow and didn't get downhearted. If you feel you are getting annoyed, take a break and leave it a few weeks and then come back to it. In my case nothing has changed much those few weeks, but I can then get the motivation back to do a few more sessions at it.

That is only my experience, obviously each house and project is different!

Merlin

 

[Penners]

There is no way I could get the motivation to do the whole lot at once. I started small, accepted progress would be slow and didn't get downhearted. If you feel you are getting annoyed, take a break and leave it a few weeks and then come back to it. In my case nothing has changed much those few weeks, but I can then get the motivation back to do a few more sessions at it.

That's good advice, Merlin. It all comes down to that old saying:

Q: How do you eat an elephant?

A: A spoonful at a time.

 

[Flyfisher]

Exactly right. I reckon I'm still only halfway up the front leg of my particular elephant, but steady progress all the same.

Regarding "A brick chisel would be too vicious and risks damaging the bricks", I wouldn't dismiss something like a brick bolster to get under the render and then lever it off, hopefully in fairly large chunks. Although, as Merlin rightly says, minimising damage to the underlying bricks is the most important thing.

 

[Merlin]

Having got back to this job this weekend, I tried with the brick bolster, but found that progress was not good.

In summary, the bolster has a much longer cutting blade than the screwdriver. This spreads the force of the hammer blow along the blade and thus ended up "bouncing" off the render, rather than getting behind it and fetching it off the brick.

Thus I tried the bolster with a bigger hammer, 1kg lump. This did reduce the bounce and cut into the render, but also cut into the brick face too.

Thus I reverted back to the large screwdriver and lump hammer. The smaller (blunt) blade on the screwdriver cut between the render and the brick without damaging the brick face. Using the bigger hammer, I found that I could control this combination better than the claw hammer, as I didn't need to try and hit the screwdriver so hard.

Obviously the laws of physics come into play here;
brute force on smaller blade gives greater penetration into gap between render and brick than equivalent brute force on longer cutting blade, (And blunt blade doesn't damage brick!)

Anyway here endeth my experiment.

Now, the next questionable experiment...

If render gets wet and stays wet for long enough, it detaches itself from the brickwork. (Based on my experience.) My next experiment is to puncture small holes into the render, a couple of mm deep, and then use a steamer to see if can soften the render first, before resorting to brute force. I have no idea whether this will work, but I have steamed artex and plaster before, so would be interested to know if steam has a similar effect on cement render.

Of course, you can all send the men in white coats round to my house if you think I am mad..... but until then I will keep experimenting.

M

 

[Penners]

. I have no idea whether this will work, but I have steamed artex and plaster before, so would be interested to know if steam has a similar effect on cement render.

I'm very dubious about that. If water gets into render, it will indeed sometimes "blow" the render away from the substrate. But this is nothing to do with softening. It's simply that, when water gets behind the render and freezes, the very strong expansion effect can push the render off the brickwork.

So, in order to reproduce this effect, you'll need to drill holes through the render (but not into the brickwork), and then ensure that there are cracks between the render and the brickwork for the water to soak into. Then you'll have the freeze the water (at a time of year when Mother Nature is increasingly less likely to handle this detail for you).

Be aware also that concrete hardens as a result of hydration, which is a chemical reaction between the cement and water. According to research by the Cement & Concrete Association, this chemical reaction can continue in tiny amounts for decades after the initial curing. So, as water contributes to the hardening process, I don't believe it's likely to be very successful at softening the concrete.

Well, that's my amateur view, anyway.

 

[Flyfisher]

Just another amateur view, but it's also my understanding that concrete hardening is a chemical process in which water helps the chemistry do its thing. Water does not act as a concrete solvent and the concrete does not set by drying out, as other substances dissolved in solvents might. At least, I've never heard of concrete dams or bridges being weakened by prolonged exposure to water. :wink:

I think Penners is right about wet or even just damp concrete being levered off walls by the mechanical action of freezing water. In fact, we have a section of cement-rendered brick wall and it has suffered badly this winter from the render falling off in places. I removed the remaining render only last week and the underlying brickwork was soaking wet. Not only has the freeze/thaw effect 'blown' off the render but it has also blown off the face of a lot of the bricks.

Fortunately it's not an old wall (about 10 years old I believe) and nothing special so there's no great loss of history involved, but it's quite instructive to see how quickly trapped damp can wreak its toll. After removing the remaining render, the soaking wet bricks dried out within just a few days (became the same colour as the previously exposed bricks), thus demonstrating how effective the cement render was at retaining the moisture that had found its way into the structure of the wall.

 

[Feltwell]

Semi-professional view - having done research many years ago on corrosion inhibiton in reinforced concrete (yes, I am in great demand for dinner parties everywhere) - and as someone who once won honoury membership of the Concrete Society for his research (Yes, it really does exist! What an honour!! :lol: I've still got the society tie somewhere!) - is that Penners & Flyfisher are both spot on. Put water on cured concrete and you get wet cured concrete. Steam will do nothing, if it did then the cooling towers at your nearest power station would be in big trouble.......

Penners is right about the chemical reaction continuing for decades, it's strange old stuff is concrete. Generally it reaches about 95% of it's "final" strength after 28 days, when you see "set" concrete after 24 hours or so it's still very weak (or "green" to give it it's proper name). It's only at about 50-70% strength after 7 days, depending on the mix. In theory concrete never stops gaining strength - it's a curve that trends towards it's ultimate limit. In practice of course it gains strength to a point where you can't reliably measure the increase any more.

 

[Merlin]

Many thanks for all the advice gentlemen.

Therefore it is back to brute force, ignorance, a screwdriver and a big hammer.

At least the concrete back yard is breaking up a bit easier, six inches thick and a bigger hammer.....

I will get a garden for Merlin Junior this year. (Hopefully it won't kill me in the process!)

M

 

[MdB]

At least the concrete back yard is breaking up a bit easier, six inches thick and a bigger hammer.....

and a big lever......

Concrete is very strong in compresion (ie when you hit it with a hammer) but weak (in comparison) in tension (ie when you lift an edge with a lever).

You may also want to tryout a £30 - £40 SDS hammer drill. It will probably only last one job but it may save your back.

 

[Feltwell]

You may also want to tryout a £30 - £40 SDS hammer drill. It will probably only last one job but it may save your back.

But get yourself some decent ear defenders though. Doing temporary or even permanent damage to your hearing by using power tools is surprisingly easy!

 

[Flyfisher]

and a big lever......

Definitely. The bigger the better. If you can raise the concrete slab even a tiny amount off the supporting ground, a relatively lightweight thump with a sledgehammer will crack it very easily, whereas pummelling away at a solidly supported slab of concrete will probably make you crack before the concrete does.

 

[Feltwell]

I would heartily recommend a 6' bar - I've had one for years and it's been great for jobs like this. Lever up one corner with the bar pivoting on an old brick, kick a bit of brick or something underneath to keep the concrete up, and then give the concrete a good whack with a 14lb sledge in the middle of the unsupported area. Subtle - no. Effective & therapeutic - yes!

http://cgi.ebay.co.uk/Newsome-6-Foo...t=UK_Hand_Tools_Equipment&hash=item3cb5758ffa

 

[Flyfisher]

Good recommendation. I have one of those as well - quite heavy in its own right and it's surprising how much leverage can be applied. The pointy end can also do a fair bit of damage to concrete on its own, especially when used near to the edge of a concrete slab. The chisel end can also be sharpened and used to cut through tree roots when digging post holes and the like. Also useful when grubbing out tree stumps to below ground level (but hard work!).

 

[Penners]

I would heartily recommend a 6' bar

Me too - although I'm not fussy about the length. Just so long as it's well stocked.