Reinforcing rods in agglos

[Ron Avery]

I am trying to build a wall using agglos, (concrete blocks with hollow chambers) there are a number of different types but the ones I have a question about are the ones for the corners and openings that have the large hole for filling with concrete and putting in reinforcing rods. The question is when do you put the rods in and how many?  The wall will be 2.5 metres high so I cannot see that you wait until its finished to try and insert a rod and then pour concrete down it, so what is the correct procedure?  Also is it necessary to put in rods at other points on a wall?  If so are these short rods, say three, four courses long and staggered along the wall's length?

Thanks in advance

[Pierre ZFP]

Far from being an expert, I researched this on www.leroymerlin.fr as I wanted to do something similar (has now risen to number 98 on my 'To Do' list) they have an advice sheet on this, with pictures!!  Have a look for

'Je construis un mur de clôture en parpaings'

under the section 'Des Conseils' and it might be what you want.  Sorry but I can't seen to make a link directly to the page of their site giving the info but you'll find it easy enough

[Ron Avery]

Thanks Pierre but this does not answer he question of when to put in the rods, on here they use a cage of four rods wired together which must be even more difficult to place in a 10 foot wall, but surely you don't have to lift each block over the top of a rod or cage to install it do you?

[Pierre ZFP]

Good point.  I am going for a much smaller wall and end post, only 1.5 M high so I had assumed the 4 post cage thingy was set in the foundation and then, as you say, the blocks passed over, set on suitable mortar then back-filled with hardcore/concrete.

For a 10 footer I don't see how this could be done but if you don't put the rods in first then how are they tied into the foundation?

We need an expert!

[Cat]

Hi Ron, I've just been out in the garden for a look at what our masons are doing, and it seems to be

Lay concrete base for wall

Whilst concrete is still wet, hammer in 1 rod vertically for every other block (they use a stick, cut to size, to judge this).  The vertical rods don't seem to the full height of the wall, but rather to a height of about 1 metre 50 cms  to tie the wall into the ground.

Lay a course of blocks

After each course of blocks is laid, lie a horizontal rod into the grooves in the top of the blocks, slightly overlapping each rod when you need to add another.

Pour concrete into top of wall.

I'd ask exactly what the "rules" are, but they're not around at the moment.

[Cat]

[quote user="Cat"]

Whilst concrete is still wet, hammer in 1 rod vertically for every other block (they use a stick, cut to size, to judge this).  The vertical rods don't seem to the full height of the wall, but rather to a height of about 1 metre 50 cms  to tie the wall into the ground.

[/quote]

 

Ooops, just went out to re-check, and the vertical rods are for every block, not every other as I first thought, but they're spaced so as to lie near the edge of the blocks (the "open" ends, rather than the hole in the middle) so that the blocks can be slid/angled into position, rather than lifted over the top.  It is only the corner blocks that have to be lifted over the rods.

Does this make sense at all?

[Anton Redman]

Builders who a re working near us cut at about 1.2 metres and allow a one block overlap when they start the next 1.2 metres.

[Ron Avery]

I have not heard of using rods in every block unless the wall is for a pool or under lateral pressure, guides say every 3 to 4 metres, if desired but not how to do it, its even more puzzling as to how its done with an internal wall that cannot be accessed from above, I was told short rods are staggered across the wall in these cases.  It makes sense Cat for the first course and for foundations but how do they get the blocks for the staggered second course over the rods as there are no holes in the centres of agglos.  Still not sure about corner ones with large hole to be filled with concrete and rods, still like to know if rods are placed before build or inserted from above and then concrete poured.

.  

[littlemouse]

Normally you would put the steel into the foundation concrete to a height of around 50 cms,then build your wall to the full height.Into the corners you would put in either 3 bars of 8mm steel or 2bars of 10 mm steel before filling  with concrete.

[Ron Avery]

[quote user="littlemouse"]Normally you would put the steel into the foundation concrete to a height of around 50 cms,then build your wall to the full height.Into the corners you would put in either 3 bars of 8mm steel or 2bars of 10 mm steel before filling  with concrete.[/quote]

Thanks, LM that is just what I wanted to know. Still not sure how this works for am "internal" wall where you cannot access the top though, I suppose staggered shorter bars would be an option?

[Cat]

You're right Ron, my wall (with vertical rods for every block) is a retaining wall.

One, perhaps silly, question though... if your wall is an internal one, and you can't access the top, how will you pour the concrete in?

[littlemouse]

You have to leave a gap at the top large enough for a trowel and fill it trowel by trowel or put gloves on and put it in with your hands .