Jump to content

Do box lintels require padstones?


Digmixfill

Recommended Posts

I'm about to fit a catnic bsd100 over a doorway, 900mm span, in a wall made of celcon standard 3.9kn blocks.

Do i need to put padstones under it or not? Original plans specified a concrete lintel without padstones.

 

I don't think I need to fit them, but i have a nagging doubt so thought i'd ask the floor.

 

Link to comment
Share on other sites

The basic principle of a pad stone is used to spread the load over a larger area than would otherwise be the case. I'm not an SE but the calculation goes something like...

 

Find out/calculate the maximum safe pressure (Newton's per square mm) that the blocks can withstand including safety factors.

 

Calculate the load in (Newton's) on each end of the beam.

 

Divide the pressure by the load to get the minimum bearing area  (square mm)

 

Divide the minimum bearing area by the width of the wall to get the minimum length of the bearing (eg how much of the beam must rest on the wall.  Regs say this must be >100mm).

 

If that minimum length is more than the beam allows you need a pad stone to increase it. (Eg if the minimum length calculates out at 240mm and your beam only allows 100 or 150mm then you need a 250mm pad stone.)

 

What I'm not sure about is how to calculate the load or the safety factor required.

 

Pad stones are more commonly required where a beam is at 90 degrees to a wall because the bearing area is fixed by the width of the wall and width of beam. Think cheese wire cutting cheese.

Edited by Temp
  • Thanks 1
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...