# What material do i need to support some bricks?



## angelboy (24 Apr 2017)

I wanted to corbel a step with a brick that steps out by half its width. I know I'm only supposed to do this by 1/3rd of the brick rather than half so I wondered if I could place a flat steel support under it and still go out to the full 50%.

Would anyone know what steel and thickness I'd need?

I can then work out whether I want to go to the expense or just knock the bricks back a touch.

I also wanted to do something similar with a fireplace mantle so I need some flat bar for that as well.

Any ideas?


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## TFrench (24 Apr 2017)

Not sure on what thickness you'll need, but if you use mild steel outside it will rust and expand.


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## Bedrock (24 Apr 2017)

Are you looking for speed or a height saving? Depends on what type of brick you are intending and whether indoors or out. Some bricks are relatively soft, or are not good if exposed to weather/water/frost. 
I think that the overhang is not just a factor of the brick strength, but also of the leverage. If you have a 16 stone man treading on the edge of the brick, it is likely to come loose fairly swiftly if used for normal domestic use. The 1/3 overhang is tried and tested over centuries. If you want to go for the steel plate, possibly stainless steel would answer, but the cost of a suitable depth and thickness of the plate, for the width of the steps might be a disincentive. I suspect that the depth of the plate should be at least a brick deep behind the brick that forms the overhang.

You would also need to look at whether you could achieve a satisfactory bedding of S/S in a Portland cement mortar, and indeed whether there would be a reaction between the mortar and the S/S.

In regard to the fireplace, last time I saw one, it appeared to be black steel, but then, in a fire place, it would be.

Sorry to complicate.

Mike


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## angelboy (24 Apr 2017)

TFrench":2olvfvkh said:


> Not sure on what thickness you'll need, but if you use mild steel outside it will rust and expand.




That's good to know. I wasn't sure if I could get away with mild steel but now I know.


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## angelboy (24 Apr 2017)

Bedrock":29xx3elj said:


> Are you looking for speed or a height saving? Depends on what type of brick you are intending and whether indoors or out. Some bricks are relatively soft, or are not good if exposed to weather/water/frost.
> I think that the overhang is not just a factor of the brick strength, but also of the leverage. If you have a 16 stone man treading on the edge of the brick, it is likely to come loose fairly swiftly if used for normal domestic use. The 1/3 overhang is tried and tested over centuries. If you want to go for the steel plate, possibly stainless steel would answer, but the cost of a suitable depth and thickness of the plate, for the width of the steps might be a disincentive. I suspect that the depth of the plate should be at least a brick deep behind the brick that forms the overhang.
> 
> You would also need to look at whether you could achieve a satisfactory bedding of S/S in a Portland cement mortar, and indeed whether there would be a reaction between the mortar and the S/S.
> ...




Thanks for you reply.

The leverage aspect was one that I was considering and I thought that I could have a plate, say 150mm wide, where 25mm extends under the brick overhang, then 50mm is actually under the brick and then 75mm is bedded under a paving slab. If a heavy bloke stood on the end of the brick then he'd be trying to lift the bedded in slab as well. That's my naive logic anyhow.

I've attached a couple of photos to get a better idea.

This is the base for the slabs and bricks - it's solid enough!






This one shows a corner pillar, with the base extending out and then an example of the paving and the side on bricks that are in question.





...and a sketch version of the same corner.





I suppose I could loose a few mil and go 60mm on the base and 40mm overhang (which is a few mil off the 1/3rds rule) and then bed them in a stronger mix maybe?

Regarding the fireplace I was told that I could go to the full 50mm but that I could only lay 1 course per da - which is OK by me if it gets the desired effect. The problem I have is a section of bricks that form the top part of the mantel. They seem to 'float' in mid-air which isn't very good really. I thought about drilling each brick and sticking some sections of rebar in them to add some strength and then prop them up as I was laying them (like you do when building an arch) so that when the mortar set they'd be nice and secure - and less likely to fall on one of the kids heads!

I don't know if you can see what I mean with these photos.

This is the idea for the fire place, the orange section is the corbelled part of the design.









...and on it's own with a shot from underneath where you can see the offending bricks that need additional support.


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## MARK.B. (30 Apr 2017)

As far as the paving goes ,i would not go out as far as you propose, setting them in another 15/20 mm would provide a much stronger bond and still look ok. The fireplace will be ok unless you are planning putting something very very heavy directly on the ends.


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## gregmcateer (1 May 2017)

I agree with MARK.B above on the steps and the fireplace.

If you really want to have the steps projecting further than 'normal' the only other way I would see it working is by inserting a 'tie' into each brick - not a normal mortar course tie, but something like a drilled and plugged rod / bolt - In effect a biscuit joint to tie each individual brick to the one behind - but depending on the size of the project, that's a helluva lot of work and pretty difficult to achieve an accurate drill hole on both bricks. 

If you are really keen on the idea, it may be worth a call to a local structural engineer to ask his/her advice - they are not usually very expensive and their knowledge is very useful/

HTH

Greg


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## angelboy (17 May 2017)

MARK.B.":2tsrwn4a said:


> As far as the paving goes ,i would not go out as far as you propose, setting them in another 15/20 mm would provide a much stronger bond and still look ok. The fireplace will be ok unless you are planning putting something very very heavy directly on the ends.




Yes, I think that's what I'll do for the paving.


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## angelboy (17 May 2017)

gregmcateer":2qe0r2su said:


> I agree with MARK.B above on the steps and the fireplace.
> 
> If you really want to have the steps projecting further than 'normal' the only other way I would see it working is by inserting a 'tie' into each brick - not a normal mortar course tie, but something like a drilled and plugged rod / bolt - In effect a biscuit joint to tie each individual brick to the one behind - but depending on the size of the project, that's a helluva lot of work and pretty difficult to achieve an accurate drill hole on both bricks.
> 
> ...




Hmmmm, biscuit jointing......I wonder if I cut some 5mm slots in the front of the supported bricks and the of the unsupported bricks with the angle grinder then set an angle iron the full length to the supported brick corbels.

The bricks are solids so no issue with cutting slots. I'd build them on a timber support until the mortar had set and it might work OK.


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