What is the correct method for installing padstones and steel pfc

[Lisa Stephens]

I have just started my own DIY loft conversion. I have already obtained planning permission and building regs permission.

I removed all of the rubbish from the loft and then had scaffolding installed.

The structural engineer drawing specifies three loft pieces of PFC steel beams which are 4.9M in length. Each steel beams sits on one C35 concrete padstone 450 X 225. I searched (Googled) for these online but I kept finding 440 X 215 sized padstones. Are these padstones the same thing?

I am also unsure on the method of installation of the padstones. Do I first install two rows of Class B engineering bricks, followed by the padstones and then the steel? The steel company quoted £600 for all three steel beams. I'm not sure if this is a bargain or not?

I did ask them to install the steel beams, but they told me it wasn't economical because it's only three pieces of steel.

 

[tony1851]

The 440 x 215 padstones would be OK for a domestic loft conversion.
The SE would have sized them to go direct onto your existing brickwork - no need to put engineering bricks in first.

 

[Lisa Stephens]

Thanks for the answer Tony1851. I have got a few more questions to ask.

Is a 3:1 ratio of sand cement accurate for a padstone mortar bed?

After I lay the padstones, how long should I wait before laying the steels on top. Is there a recommended amount of time to wait in order for the mortar to fully dry?

Are the steels layed on the padstones with or without mortar being applied?

 

[John D v2.0]

Steels go directly on the pad stones, you have to let the mortar go off before putting any load on, but don't trust us on here, your SE should specify as he has professional responsibility for correctness.

 

[tony1851]

As above - nothing between steel and padstone. 24 hours should be fine.

 

[Deleted member 174758]

On the rare occasions when we need to add packers we tend to use solid steel shims which come from structural steel fabricators in various thicknesses.