50mm vs 65mm Screed

[Boyblue]

Some B&B manufacturers specify 65mm and others 50mm.  The beam sizes are similar if not identical, so what is the unseen, that causes the difference in specified toppings.  Might it be the number or placement of reinforcement wires, the strength of the concrete, the shape of the beams?

 

 

[nod]

It’s normally 50 or 75 

Flow or sand and cement 

The type of BB doesn’t make any difference 

Both are good options 

[Boyblue]

1 hour ago, nod said:

It’s normally 50 or 75 

Flow or sand and cement 

The type of BB doesn’t make any difference 

Both are good options 

So, specifications given on the company websites are for a fixed set of variables.  Once one variable changes (like requesting a 50mm screed), everithing else does? Once a specific order is made and 50mm screed is requested, the appropriate configeration will be detailed? 

[Gus Potter]

One secret of self building is to work out where level and dimensional tolerances really matter and where they don't.

 

You want to keep you options open in terms of what your local trades can deliver. Looser tolerances can drive down the build cost.

 

22 hours ago, Boyblue said:

Some B&B manufacturers specify 65mm

Work on 65mm for now and your life will be a bit easier. Beam and block joists have a camber due to the prestressing but the camber is not even!

 

The precast folk cast the joists on a long line and cut them to size after curing. The prestress in the cast line varies from end to end so some joists have diferent levels of prestress and thus different amount of cambers.

 

 

 

[nod]

6 hours ago, Boyblue said:

So, specifications given on the company websites are for a fixed set of variables.  Once one variable changes (like requesting a 50mm screed), everithing else does? Once a specific order is made and 50mm screed is requested, the appropriate configeration will be detailed? 

No

The covering that goes on the top of the BB makes absolutely no difference to the BB designer