Structural issues and brick spalling

Eversonclaire

The cement render on the back wall of my Victorian house is badly cracked and there's damp and cracks internally. I partially removed some render to find out if it was brick or stone (the front is stone and brick) and it's red brick which is badly spalled and the mortar is crumbling and gone in places.

A renderer has just been and looked amused when I said I'd read that the correct remedy is to remove the damaged bricks and replace with new, one by one. He said he sees this all the time and the solution is to render over with a form of glue to seal the bricks. A lime specialist I've been talking to, and from the little I have read, said cement render on an old building is a disaster. 

I am also worried about the structural safety of the wall.  Underneath the bottom of the render, at the bottom of the wall, appears to be a gap and surely there should be bricks there?? I assume I should get a structural engineer in first and get advice? Very worried about the cost of it all as have a limited budget.

Grateful for any views on the repair with just render and if that would just be postponing problems for the future? 





The gap underneath the window. There's a drain directly in front :


Internally there are cracks and the plaster appears to be being pushed off the wall as it's bulging

The ceiling is also cracking:

stuart45

Lime render is a better solution than cement render. Cement render tends to trap any damp in the wall. Sometimes in the winter you find water trapped behind cement render when it blown. Looking at the back of the house it looks like there will be a fair amount of cash to be spent to do the job properly.

Eversonclaire

Thanks, @stuart45, that's what I was fearing. I am speaking to the lime renderer later, hopefully, but I am assuming to be able to render with lime, the bricks would have to be replaced and can't just be rendered over?  So the cost would be further increased.  

stuart45

You will have to assess the brickwork once the render has been hacked off.  The lime plasterer should be able to advise. 

FreeBear

Difficult to diagnose the gap where the manhole cover is. It looks like it may just be where the bell cast finishes, but then again, there does appear to be a void. Someone needs to get down on their knees and have a good poke around in there.

Other issues that jump out -

The downpipe is not connected to the diagonal section - That is going to result in rain water soaking the wall, but I'm guessing you alread know this.

The concrete is way too high. At least 2 inches above the manhole cover, and quite likely bridging the DPC.

If you have a suspended timber floor inside, you are missing air bricks at the back which will result in joists & floorboards rotting.

That cement render needs hacking off and the wall repointed once the bulk of the cement has been raked out between the bricks. A generous layer of lime render over the top will hide the spalled bricks and any messy pointing - As long as the bricks are still sound, you shouldn't need to replace any of them.

Internally, you have significant damp issues - Most, probably a result of water being trapped in the walls by the external render. The cracks will be down to the original lime plaster having blown. Hacking off and replastering in lime would be the preferred fix.

Removing more than 25% of the render or plaster would trigger building regs compliance - Building control would want you to insulate the walls to achieve a u-value of 0.30 W/m²K - Up to you if you involve BC and get the work signed off.. For a solid brick wall, you want to use wood wool, cork, or some other breathable insulation and not stuff like EPS or Celotex/Kingspan. Don't waste your money on hemp renders as you can't get the thickness to satisfy building regs easily.

Eversonclaire

Thanks so much for commenting, @FreeBear.  The gap is most certainly a void.  It is difficult to capture in photos. I can't see any brickwork, and the area runs at least 90cm across by a few inches or more deep.  It is under the window, and I don't think (hope) it goes all the way across the wall. 

There was decking above this point when we bought the house 12 years ago and we only saw this gap when we removed it the other week.  The decking frame was fitted into the gap.  The ground had been excavated and the original concrete taken away to fit the decking I presume, so the ground level was a foot or so lower, and just clay soil with the decking frame on top. We plan on having a patio so the builder has very recently filled the area with hardcore and did it up to the existing drain levels, which were governed by the old decking.  I had no idea that it should be lower than it is.

The floor is concrete I believe, not suspended timber.

I will definitely be going the lime render route, though I realise it will be considerably more expensive than the £3170 I have been quoted for cement render and repair.  The lime plasterer has said it could take up to 7 weeks as a 2 man job to do the whole house, and that would be priced at £8500 if it takes that long. I've no idea if that's a reasonable price or timescale?

Internally I do assume that the majority of problems are from the cracked exterior render, but I am still very worried by the gap and possible movement. The skirting boards in both the downstairs and upstairs rooms are coming away from the wall.  There are also internal stepped cracks on the wall perpendicular to the external problem wall, - this is a shared solid brick wall I believe.

Thanks for advice on insulation, not even something I had considered.

FreeBear

Eversonclaire said: I will definitely be going the lime render route, though I realise it will be considerably more expensive than the £3170 I have been quoted for cement render and repair.  The lime plasterer has said it could take up to 7 weeks as a 2 man job to do the whole house, and that would be priced at £8500 if it takes that long. I've no idea if that's a reasonable price or timescale?

Rendering or plastering with lime is much more labour intensive than with cement or gypsum. Lime requires "floating" several times whilst it dries to compact the material. Unfortunately, lime dries & cures much more slowly than modern materials. But I would expect the rendering to take about a week to actually apply. Most of the time estimate will be in removing the cement render and making good the brickwork it is once exposed. If you wanted to save money, you could have a go at chipping off the render yourself...

I've been hacking render off here - An air powered chisel from Lidl is both lightweight and easy to use, but I could do with a bigger compressor... Certainly easier to use than an SDS drill/chisel combo and much, much quicker than a hammer & chisel.

With your patio area, I'm afraid you really do need to reduce the level quite a bit. Putting slabs on top of the hardcore is going to raise the ground level way too much. Your builder should have been providing guidance rather than just tipping material & taking your money. Has he said anything about the void under the window or made suggestion as to what to do about it ?

Apodemus

You'll be able to see much more of that void once the render is removed.  It looks to me as if that was once a doorway, later converted to a window, so I wouldn't expect the infill below the window to necessarily match that on either side.   Its very possible that the door was converted in as cheap a way as possible and without extending the damp course along the wall.  As mentioned above, you need to work out where your internal floor level is and match that up to the external wall, so that you can make sure the your damp course isn't compromised.  

I'd be another vote for going with the lime render and I would also probably trust the lime guys for advice much more than I would anyone who wants to use cement anywhere near your building.

stuart45

Lime Render of Victorian Stone and Brick House — MoneySavingExpert Forum

Looking at your quote, there is a fair bit of OPC going into some of the mix in places.

Eversonclaire

Thanks @FreeBear I'll get an air powered chisel and maybe have a go ourselves to reduce labour hours.

The guy due to lay the patio is not a general builder, so is only doing the patio work. He got some labourers to put in the hardcore to make the ground more usable whilst I wait for the slabs (he's really busy), though it does sound as if he should know that it's too high, though he wasn't here with them, I'd assume he would have given them directions...sigh.

I asked the opinion of a mate who works for a structural repair company about the void and he said from the photos he suspects the drain has leaked and washed away the foundations. Says major job of repair of drain and underpinning probably and I should contact my insurer.  

I had a roofer here today (to look at the roof, not the void, obviously...) who took a look at it and his view was I should just 'chuck some cement in. That's what I'd do if it was my house...'!

@Apodemus thanks for taking the time to comment.  I suppose that could be a possibility and guess until I get an opinion from someone in the know that views it in person, I won't be sure what's exactly the issue.  

@stuart45 yeah, that is because the quote I posted originally was on the assumption that the back wall was stone with brick edges around the windows, and that the extension was a more modern one, hence using cement on that part of the structure. It now turns out it's all mostly red brick, just a small additional extension that is breeze blocks.  I have spoken to the lime renderer who said they can work with the damaged bricks and are used to doing that, so it's not a problem. 

I'm filling the depressed void that's opened in my mind with wine.  

FreeBear

Eversonclaire said: I'll get an air powered chisel and maybe have a go ourselves to reduce labour hours.

As long as you have access to a decent sized compressor, an air chisel is the perfect tool. I have a 7cfm/25l jobbie, and it isn't really up to the task of powering the Parkhurst chisel.

As for your slabs, they want to end up being ~150mm below the level of the damp proof course - This may mean having to lower the level of the manhole cover.. Assuming 50mm slabs, the layer of hardcore needs to be 75mm lower (a total of 225mm below the DPC). That gives you 25mm of mortar to bed the slabs down on, and it needs to be a full bed, not five blobs of mortar. A useful site for paving - https://www.pavingexpert.com/layflag1