Building/Reinforcing Leca Wall against Slab. Soil Pressure?

[stefanlaurelii]

Hello!
I am building a garage about 7x6m.
I have blasted down and am casting the slab with Dorocell edge elements for 30cm ground insulation.
Then I will build up the walls with LECA blocks.
I will refill about 2m against the side walls and the back wall.
The garage will also have a loft with a wooden beam floor and a sheet metal roof.

I am wondering how to attach/reinforce the walls to the slab and how much reinforcement is needed horizontally and vertically to withstand earth pressure, etc.?

What dimension should I choose for the LECA blocks?

What is good to prepare before I cast the slab?

Thank you kindly in advance,
Sincerely,
Stefan

 

[bmx]

hello,

I didn't think about this before and ran into some issues.

I chose isoleca which has poor strength compared to regular leca, so choose regular if you can.

Generally speaking, leca is good at handling pressure from above but not from the side (i.e., wind loads and earth pressure).

With isoleca, you can expect that a wall (2.4 m high) should not be longer than about 2.5 meters if you backfill with regular gravel without any supporting partition walls (like a T). I found a formula for this in the design instructions that you can find at www.maxit.se.

I had a wall of 5.2 m which I filled 2.4 meters high against and did two things:

1. built a dividing interior wall of 2.6 m that I reinforced with upright rebar and 8 mm rebar in every other row.
2. backfilled with 4 m3 of leca balls purchased in bulk bags.

It went well.

 

[matbr107]

You can also fix the first shift of leca by recessing in the slab when you cast. This was done on our basement floor this summer. See picture at:

www.villabroden.se -> Photo album -> Groundwork -> "Recessed to fix the first shift of leca"

We also have three brick support walls to take up the ground pressure against the wall that is below ground level.

GOOD LUCK!

 

[stefanlaurelii]

Thanks for the tips and interesting to see the pictures of the construction.

How do you make the chamfering for the Leca blocks in the finished slab?

Since this is a garage, it's not suitable to have partition walls along the length. Therefore, some form of other vertical reinforcement is needed besides the edge?

The contractor I've hired for groundwork and slab suggests that I reinforce and cast vertical reinforcement beams in the slab, which are also securely attached to the longitudinal reinforcement in the Leca.

I think this sounds reasonable, but I have no experience, so comments are gratefully accepted.

Best regards,
Stefan

 

[anbygg]

You can also fix the first shift of leca by phasing out in the slab when you have cast it. This was done on our semi-basement floor last summer. See picture at:

www.villabroden.se -> Photo Album -> Foundation Work -> "Phased out to fix the first shift of leca"

We also have three masonry support walls to absorb the ground pressure against the wall that lies below ground level.

GOOD LUCK!

Just a small comment, calling clinker blocks from Finja Leca maybe Maxit might have some views on..

 

[matbr107]

The actual "phasing out" is done by simply removing the concrete with a tool like a shovel after it has cured for a few hours and is a little easier to work with!

 

[frenchie]

Since this is a garage, it's not suitable to have partition walls along the length. Therefore, some form of additional vertical reinforcement beyond the footing is needed?

The contractor I've hired for the groundwork and slab suggests reinforcing the slab and casting vertical reinforcement beams, which are also reinforced with the longitudinal reinforcement in the Leca. I think this sounds reasonable, but I have no experience, so comments are gratefully received.

Hi Stefan

I'm dealing with the same questions as you. My garage will be 18x9 meters. I have bedrock exposed around and virtually no ground pressure to consider. The upper short side of the foundation will be as low as one course of LECA blocks. The lower short side will average 2.5 meters (!) with the lowest cavity in the rock at 2.8 meters. I've been advised to completely skip casting a footing in stages and instead pre-drill for rebar (reinforcing bars that stick up in the first course of LECA blocks) and then form the blocks and build directly against the rock. This assumes that everything is thoroughly cleaned, meaning the pressure washer will be working regularly.

Then I'll reinforce every third course with horizontal reinforcement in the tracks of the LECA blocks. Just like you're considering, I'll make a couple of "interruptions" in the foundation wall with standing reinforcement to cast "columns" inside the masonry.

According to the skilled and experienced bricklayer I consulted, no supports are really needed on either the inside or outside of the tall, lower masonry. But I'll still add a substantial earth mound on the downside when everything is complete. This will provide natural support about 1.5 meters up from the bedrock. Since the reinforcement is inside the masonry, the wall will be so strong that it won't give way (according to my bricklayer). Otherwise, I considered forming a (there's probably a nice name for such a support) slanted reinforcement on the inside of the wall in connection to my two embedded, fully reinforced columns. It would be even worse to cast these supports outward, but then it wouldn't be as aesthetically pleasing.

The entire wall will be built with 25x19x59 stone (meaning the wall will be 25 cm thick, each course 19 cm high + mortar joint), the final course of the wall I'll use a 9x19x59 block but then I'll attempt a small special feature;

Under the places where the frame will be anchored, I'll let the slab extend all the way to the edge (placing a slab against the wall outside as a casting form). This is because I want the frame to stand all the way out to the edge of the slab. Why?

Well, my idea is that the frame stands on the outermost edge, the sheet on the outside is more or less directly attached to the beams and extends down over the slab's edge. In the roof, I'll leave air gaps (roof sheet, I-beam, insulation) between the I-beams. Then I'll vent the air at the ridge and choose to either simply vent it out or, through simple plastic pipes and a PC fan, blow it out at floor level. The idea is that this will keep moisture away during spring & summer with extremely low energy consumption. I mean a metal roof is quite a neglected solar collector that is usually left as is.

As you may have understood, the entire frame, walls/roof, will be welded up of I-beams. I'll send the plans to a local construction consultant for strength calculations as soon as the drawings are ready (this week?). The wall elements will be welded in place standing on welded plates cast into the slab. The whole idea with the garage is to accommodate a two-post lift under the ridge. The requirement is that a VW bus can be lifted 2 meters without issues. So, I can't use wooden trusses with struts and other clutter in all directions. I want a very open solution despite the span being the entire 18 meters.

 

[Legendarisk]

Hello!
I found this thread after searching for the problem on Google. I have a few questions for you, Frenchie.

1. Do you only need to reinforce every third row? Or am I misunderstanding you here?

2. Does it work well to clean the wall with a pressure washer and how clean does it need to be?

Thanks in advance.

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