Mortar thickness joint

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Hi,

After laying a row of foundation blocks some of the mortar joints (vertically) range from 15mm to 20mm.

Mostly it will be a dwarf wall but on ones side it will be a maximum of 2.5m from the blocks.

I just wanted to check that should still be structurally ok?

Thanks
 
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Ideally the thinner the mortar joint, the better; 10mm is the usual for modern work.
It won't collapse, but 15-20mm...?? Has your bricklayer used a shovel instead of a trowel??
 
Lol, no I am laying them myself.

Being foundation blocks they are very hard to work with and when making sure they are plumb etc any tapping causes the joints to open up and also the whether hasn't helped as the blocks absorb it so much.

I tried to keep them at 10mm but it was difficult!

i will be fine with the rest but these foundation blocks are awkward!

:)
 
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Are you laying them to a line?

You should not be tapping the blocks much, but laying just enough mortar so that you can just rub them forward and backward by hand to get them down to the line and level, and then a little tap to close the vertical joint and/or to move the top arris to the line.

If you are hammering them, you are using too much mortar.

As it is rendered, don't worry too much about each individual block's face being plumb, but just aim for the top arris to be to the line without touching it.

Tap the blocks to close the vertical joints to 10mm or there abouts. There's no reason why they should open up. Tap the opposite end of the block in the middle with a lump hammer.
 
Yes woody, I am lying them to a line and also checking they will line up with my dpc line with a spirit level to be sure but they are all in line correctly. Yes I probably am using a bit too much mortar but I was moving them back and fourth to get the level right. I only used a lump hammer but since I have been soaking the blocks it has been a lot easier. I think the mortar being absorbed was causing me problems.

I will be working on the second course of them today and will use less mortar and make sure it is a 10mm joint.

I just wondered if I should be worried about the joints being larger on the first course but they will be below ground so I don't think they will be going anywhere.

I managed to get the ones on the higher wall about 10mm its just the other sides.
 
Don't worry about anything in the ground. As long as the joints are near enough and full, they are fine.

Likewise for plumbing and levelling. Don't keep checking every block. Just lay to there line and leave it. It all evens out in the end.
 
Ok woody. I will lay the arris to the line, that's what I did initially and was conserned because once they dried I realised they weren't completely plumb.

Also the second course (corners) I started have 20mm horizontal joint. I have my gauge rod I made to blame for that one. It does actually help me because i won't have to gradually increase the next two courses so much to get where I need to be.

I assume the same applied and I don't need to worry about those? That joint will also be under the ground. as I said it will all be rendered my concern was structural more than anything
 
Having said that my house dpc has a 30mm joint and that haven't gone anywhere :)
 
Make sure your mortar isn't too stiff and when laying to a line don't let the block/brick touch the line. Make sure there's always a small visible gap.
 
Thanks Jeds, yeah I am leaving a very small gap along it. I made the next lot a bit wetter seems more workable.

So a 20mm horizontal joint is ok for one course? Seems a bit pointless to rip up 8 blocks just to reduce the joint to 15mm. The next two courses need to be just over 10mm to get to the dpc anyway and decreasing my 20mm joint would then mean the next two courses need to be probably 15mm.

Perhaps I'm worrying too much! Lol

Cheers
 
It's quite common on site for block joints to be a bit thicker. In theory they should be around 10mm, but it's easier to get a brick down to that than a block. Look around at blockwork and you'll see some Sunday roast joints.
 

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