Bricklaying problem...

[drjim]

Chaps

Been building a barbecue and tandoor oven. It was a hot sunny day - 23 degrees according to the car when I nipped out. Built probably too much in one go for an amateur, and ended up with the top few courses wonky not good enough as I got more tired - have taken them off to redo this morning. The Wife decided there were wonky bits while I was at work yesterday, and got me today by saying "you won't be happy leaving it like that either" sadly she was right.

While I was building I noticed sometimes the mortar just went dry and sandy, and wouldn't "stick". Sections of it are fine but when taking bricks off today there was variable resistance. I am using tarmac bagged general purpose mortar, and it didn't seem to matter if I mixed small amounts or large, it seemed to be hit and miss.

I am wondering if I didn't mix it enough, and/or maybe didn't stir it up enough when I got another batch out of the big bucket. It didn't seem to be going off/setting in the bucket. I scraped up all the loose stuff and stuck it in the base of the tandoor oven section to fill it, it has set solid but seems very crumbly.

Anyone got any suggestions as to what I am doing wrong, having just dismantled about a third of what I built on Thursday, I want to make sure it goes right when I rebuild!

Wish I'd gone for the welded metal version now!

Cheers

Jim

 

[rtbcomp]

Sounds like the mortar mix has gone off slightly in the bag due to moisture getting in.

 

[drjim]

They appear to be sealed plastic bags, but I like that suggestion - makes it not my fault!

I was thinking of grabbing a small bag of cement and putting some in the mix, or would I be better just mixing from scratch with sand and cement?? I have 4 bags of the stuff left which I can take back. I'll need more to finish the thing off anyway.

Cheers

Jim

 

[Gritineye]

That premix stuff is usually made with washed sand with a plasticiser added, and is probably too hard for use near a fire due to it not being able accommodate the expansion/contraction.
I have been building for 30 yrs and I find it is not at all easy to use, just can't get on with it, so it's not only you!

It goes dry because there is not enough fat in it to retain the water in the mix long enough for you to use it, especially with hot bricks!

For that job it would be much better to use some unwashed building sand mixed with hydrated lime and cement, say around 9-2-1 ratio, you will be amazed how your skill levels improve...

 

[Sid]

Sounds like builder error to me.

If the mortar is going dry as you use it, add some more water and mix it up again. It should then 'stick' better as you use it. You can still use mortar hours after you first mixed it (longer on cold days), although naturally the quicker used the better.

Understand that mortar hardening is not a drying process, it's a hydration process, and that process takes a while. Brickwork is fairly easy to take down within a couple of days, however much less so a week later.

As gritineye says, it's not likely the mix will be nice to use anyway. Bricklayers use plasticisers to improve the handling of the mix (or fatten up as mentioned). Lime does this as well. For such a small project forget the lime (which is not nice to use), and you'll have a lot of plasticiser left over if you buy that. So as an old school bodge, you can add a tiny amount of washing up liquid. Makes lovely muck.....apparently. None of this is needed though, just add water.

How wet you mix the mortar also varies. Dry porous bricks will need a wetter mix as they suck the water out of the mix. You'll want stiff stuff for engineering bricks.

Good luck, and don't test the strength of the work on the following day.

Oh, and if moisture had got to the bag, you'd have obvious lumps in the bag.

 

[Davek0974]

+1 on a squirt of fairy liquid, works a treat.

 

[pedrobedro]

Soak the brick in a bucket of water before you lay it. Brickies on site have gobbo delivered in tubs or an onsite mixing and storage facility these days. For laying bricks I use about a 4 sand to 1 cement mix, yours sounds like the old school plenty to one It does sound like you need to mix more, turn it over lots so it all looks grey before adding water then mix it a lot more and when it's mixed with enough water (which is probably a lot more water than you think you should need) it should just hold it's shape when you scribe a line in the top with the point of your trowel.

 

[drjim]

Sounds like builder error to me.

That was what I thought - bad workman plus mediocre tools equals problem!

 

[mike os]

bagged mortar is crap... no other word for it....

building sand, lime & cement for a job like that probably 6-7:1:1 would be my guess

 

[outofthefire]

Washing up liquid might make it easier to work but its bad and I was told at college never to use it cant remember exactly why, its a few years since I was there, think it was to do with the bubbles leaving it porous and weak. It probably wont matter too much for a barbecue though.

If you use your ready mix i'd give it a good mixing dry first then add your water and mix well.

If the joints are a bit powdery on what your leaving up i'd rake them out so there about 20 mm deep and repoint them. Its not really the right thing to do but its not a big structure so it should be ok.

 

[KemppiFrog]

Old rule for concrete and cement. I day to stand on. One week to build on. One month before it is up to strength. Then it continues to go off for months. So testing after a day would find it weak. Also, not so much for brickwork, but for slabs, keeping it damp after laying is important. The correct mix of water is less than one thinks and it can evaporate after laying. So damping it down from time to time helps the process.
KF

Never tried bagged morter, so no idea there. Wetting bricks is important, otherwise they draw moisture out of the mix. Wonky lines= finger trouble

 

[Sid]

Soak the brick in a bucket of water before you lay it.

No! You'll end up with water running, washing out cement from the mix and staining the facework. It'll be comedy to joint as well. Fact: if you want a bricky happy, keep his materials dry! (Oh and make him plenty of tea and bacon rolls )

Washing up liquid might make it easier to work but its bad and I was told at college never to use it .... It probably wont matter too much for a barbecue though.

Oh it's not right, and I'd never use it on a house, no need, we have the proper gear!

TBH, a little 'magic' in the mix isn't the real problem....It's being built by a doctor.

It's only a BBQ. (Oh and a little 'rustic' look can be nice.) Good luck drjim, and remember a project needs photos.

 

[drjim]

TBH, a little 'magic' in the mix isn't the real problem....It's being built by a doctor.

I would tend to agree with that, I'm the wrong sort of professional!

It's only a BBQ. (Oh and a little 'rustic' look can be nice.) Good luck drjim, and remember a project needs photos.

And I agree with that even more, but in 5 or more years time I want to look at it and be proud of it, rather than thinking "I wish I'd relaid those wonky bricks"

I think thorough dry mixing of the readymix stuff, then keeping it at the right consistency will be the key. There are places where it is bang on and looks like proper mortar. I can get sand/cement from B&Q tomorrow or builders merch on Monday, but the other stuff is here so I might as well give it another go.

I'll report back with pics tomorrow, hopefully get a bit done. If nothing else I can finish making the tandoor pot section.

Thanks for all the advice chaps.

Jim

 

[outofthefire]

Another thing if your slow because your a beginner mix a bag dry then only mix up half at a time with water.