Installing pad stone for RSJ

[Pengwyn]

Hi there. Thanks in advance for assistance given.
I have removed the brickwork to install the padstone. Padstone size is 420x220x100.
Working back from the joist to the existing wall I have 470. Steel is 202, padstone is 220, leaving a nice 50 mm to fill in.
Am I best filling this with a cut down brick or can I fit the padstone straight onto 40 to 50 mm of 2.5/1 mix.

Also the padstone is not square on the top edge but slopes slightly. Abit of a pain this.
Any advice?

 

[tony1851]

can I fit the padstone straight onto 40 to 50 mm of 2.5/1 mix.

No, because at that thickness, the bedding will be comparitively weak in compression. Use solid masonry (cut down flagstone?) or a couple of pieces of steel plate.

 

[RonnyRaygun]

can I fit the padstone straight onto 40 to 50 mm of 2.5/1 mix.

No, because at that thickness, the bedding will be comparitively weak in compression. Use solid masonry (cut down flagstone?) or a couple of pieces of steel plate.

Tony, I'm not saying you're wrong, but just wondering what your opinion is on the following:

If M12 mortar is 3:1, and 12N/mm², wouldn't that be strong enough to bear a pad stone onto? I mean, I wouldn't want to bear a beam directly onto 40 or 50mm of mortar, but I can't see why there should be a problem if the load has already been spread by the pad stone. It's not going to be more than 12N/mm² is it?

Although if I was asked on site, I would probably say what you said above!

 

[tony1851]

can I fit the padstone straight onto 40 to 50 mm of 2.5/1 mix.

No, because at that thickness, the bedding will be comparitively weak in compression. Use solid masonry (cut down flagstone?) or a couple of pieces of steel plate.

Tony, I'm not saying you're wrong, but just wondering what your opinion is on the following:

If M12 mortar is 3:1, and 12N/mm², wouldn't that be strong enough to bear a pad stone onto? I mean, I wouldn't want to bear a beam directly onto 40 or 50mm of mortar, but I can't see why there should be a problem if the load has already been spread by the pad stone. It's not going to be more than 12N/mm² is it?

Although if I was asked on site, I would probably say what you said above!

Ronny; I don't disagree on the theoretical strength of the mortar, but at that thickness I just wonder if it would be reliable? I always thought that - if possible - it was best to bed the steel direct onto the padstone (or some equally un-yielding material), rather than on (hand-mixed) mortar.

 

[RonnyRaygun]

I always thought that - if possible - it was best to bed the steel direct onto the padstone (or some equally un-yielding material), rather than on (hand-mixed) mortar.

I agree, but in this case the beam would be bearing onto the pad stone wouldn't it? The pad stone would be sitting on the mortar?

Having said that, I can't think of any reason not to do what you suggested, as it's clearly the best option.

Starting a new job on Friday and still trying to fill gaps in my knowledge

 

[Pengwyn]

Forgive my nativity guys, I am an engineer and like to have all of the answers, no matter how silly the question.
Should I put the "flagstone" material straight onto the existing block and fill with mortar or onto a bed of mortar, and then place the padstone onto a bed of mortar also?

Considering the padstone top is slightly slanted is this an issue?

 

[RonnyRaygun]

Forgive my nativity guys, I am an engineer and like to have all of the answers, no matter how silly the question.
Should I put the "flagstone" material straight onto the existing block and fill with mortar or onto a bed of mortar, and then place the padstone onto a bed of mortar also?

Considering the padstone top is slightly slanted is this an issue?

If your pad stone "top" is slightly sloping, can't you just turn it over and bed it into mortar so that the top and sides are level / perpendicular?

You will need a thin bed of mortar above and beow to bed the packer material into.