Mortar / block laying questions

[rcx132]

Heyho,

I recently started building a compressor hut to store the compressors behind the garage to reduce noise. The walls are made from breezeblocks. The walls are done now so questions are a bit retrospective, but will be good to know for next time.

Should mortar be mixed up runnier than you would mix up say balast for foundations or sharp sand mix for rain channels etc. Was always taught that runny concrete is weaker, but with mortar would runnier mean it's easier to level the bricks and you'd get better penetration/bond with the bricks?

Does mortar just seem very weak compared to a sharp sand/balast mix? Is that intentional to allow movement?

How long for the mortar to gain strength? I left it 5 days but when I drilled the corner block it came loose. When I checked how strong corner bricks are on old walls, no amount of kicking would dislodge them, seemed much stronger than my breeze block wall. Don't know if it's a question of time or I did something wrong.

I mixed 1:5 cement/building sand according to instructions on the cement and added plasticer according to instructions.

Looking at the garden walls in my area (next to London), the mortar seems to be using sharp sand and not building sand, could that be right?

 

[Shox Dr]

5:1 is a bit weak. 4:1 is better. The key to good mortar is air, you need tiny bubbles, so as you bed the brick/block on the bubbles colaspe allowing the mortar to compress.

Did you use a plasticiser

 

[rtbcomp]

I was told by an old boy that mortar keeps bricks apart, it doesn't stick them together. It's the weight of the courses above that keeps the bricks in place, which is why it's easier to dislodge bricks from the top of a wall than lower down.

 

[slim_boy_fat]

I'm no builder, but I'd imagine "runnier" wouldn't give sufficient strength for the blocks.

Won't be long before someone with proper experience comes along with the proper answer.

 

[gaz1]

5-1 is for internal brick building
4-1 is for mixed outside and inside
3-1 is your standared mix

any of these mixes can be used inside or out however pointing is needed on the first 2

as goes for the mixes between wetter or thicker mixes the builders use a wetter mix as there are able to speed build in a day the rule of thumb. put cement on the bricks and push or lightly knock into line move onto the next brick if you have to hit hard its too thick also too wet where it slops out is a no

this is different between builders some dont put cement on end of brick some do the reason for this is speed laying of the bricks the mortar is squeezed down when you next cement up and further pushed down as you line the brick it dosnt fill it all then they point it up afterwards

heres a tip after pointing use a soft brush and sweep the bricks as it cleans off the loose cement

 

[slimjim]

You need the right amount of plasticiser, and the mortar should be the consistency of whipped cream, i.e. It should peak and not slump,

Don't use old plasticiser, it goes off

 

[Fazerruss]

A squirt of washiwashing up liquid

 

[8ob]

A mate of mine built a 60`ferrous cement motor sailor boat, basically a load of steel hoops with acres of chicken mesh and plastered with cement. Anyway this went on for years so cement and the curing of was one of the things he would drone on about. Not to be quoted on this but he reckoned that if cement goes off too quick it just turns to powder. His boat was plastered in a tent in one hit and steam was injected into this tent for twentyone days to cure , thats how long moisture needed to be present. Often wonder with bricks and blocks being so dry whether the quick drying is what kills the cement irrespective of the mix. Just thoughts and ramblings.

Bob

 

[rtbcomp]

^^ I suspect if cement dries out before it has had time to react with the water you'll end up with weak joints.

 

[Kayos]

An old builder told me it should be the consistency of cow pat (he was a country boy) I only do patching but that's how I do it without problems

 

[hunter27]

If you want to see a good bricky at work look no further.

I doubt many local building firms could do this the same way as he does it
pete

 

[Mikey D]

I think with those aerated blocks you've used (thermalite) you need to water the blocks first so they don't suck all the water out of the mortar too quick ? Mind you I could be wrong it's been a while since I did much building work

 

[gaz1]

the closest i can find is this

but this mix is too thick for bricklaying around 2.26 is a little too wet but close to the builders mix they use

 

[pedrobedro]

I use 4:1 for block and brick and you should be able to make a V in the surface of your gobbo with the tip of your trowel like a furrow which doesn't fill back in.

 

[eSCHEn]

An old builder told me it should be the consistency of cow pat (he was a country boy) I only do patching but that's how I do it without problems

Ditto. Plus it means you can hoik it in with your hands (spades in my case) and it sticks nicely.

 

[Wendelspanswick]

I've done a fair bit of block laying and laboured for my FIL who was a full time brickie before he retired.
Always 4 parts sand to one part cement, a small splash of plasticiser and be frugal with the water when mixing, it's easier to add more water if the mix is too dry, too wet and you have to add alot more sand and cement to get the right consistency.
The right amount of water one day could be too much the next day if it's rained on your sand or your near the bottom of a dumpy bag.
You need a drier mix for medium density blocks and a wetter mix for light weight blocks (aerated) as they soak up the water quickly.
You need to gauge the same amount of mortar on each block and run the point of the trowel down the centre to create 2 'furrows' which flatten out as you tap the block down.

 

[julianf]

A squirt of washiwashing up liquid

Really bad idea. Maybe in the past, but it contains more than just soap now.

 

[angellonewolf]

i general do 1/3 for a strong mix if doing small stuff

1/4 if mixing for laying bricks dash feb mix or still use washing up stuff if push comes to shove would not do this if builing a house but a quick fix on a garden wall putting up 10 bricks near the top

 

[Fazerruss]

Really bad idea. Maybe in the past, but it contains more than just soap now.

Been doing it for the last 20 years to pressent and none of the buildings have cracked, fallen down or need repointing. 2 conservatories, 3 porches , 3 walls and 2 garages and ridge tiles. Total aprox 7000 bricks + blocks.
The secret is not to go daft with it, the cheapo no frills stuff is what I use. I even used car antifreeze in winter as a cheap alternative for frost protection while bricklaying in near zero degree weather conditions.

 

[angellonewolf]

^^^^^^^ just goes to show dont need expensive adds to make a job good