Urgent assistance: Constructing Flat roof stuck with a problem

[Hemant]

There appears to be an issue with the height of the new flat roof on the rear extension. The increased height doesn't leave enough space for proper flashing installation (clashing with Window). Unfortunately, we can't lower the steel beams as they have been welded. Could we discuss potential solutions to address these concerns?

[twice round the block]

Remove 3 courses of brickwork all round to get back to the level you should be at.

[Hemant]

Thankyou for your reply, does it mean moving the beam lower ? If yes, it is very challenging as it has been welded at the other end.

[twice round the block]

Can't you put joints into the RSJ void 200mm, put the insulation between them, plasterboard below and ply sheets above, then flat roof membrane.

 

Is the drawing you've posted correct?

I'm not sure why it shows plasterboard above the RSJ.

 

[Carrerahill]

My thoughts are:

 

1. Replace the window above with a smaller one and brick up to new sill height.

or

2. Redesign the roof so the insulation is within the depth of the steel and board out just above steels for roof deck. Even at that, flashing detail won't be 100% but can work because you can use the sill in your favour to get a good seal to the flashing. You are meant to have 150mm upstand then dressed into brick, but in fairness, I have 75mm flashing upstand which I dressed in under windowsills.

 

Who made this mistake?

 

Edited June 7, 2024 by Carrerahill

[Conor]

We had this issue, BC insisted we raise the sill up two courses to get the min 150mm flashing... Of course that meant new window. We couldn't lower the roof. Luckily, all of this was spotted by my builder at a very early stage.

Edited June 7, 2024 by Conor

[Hemant]

Thankyou Carrerahill and Conor. 

The mistake was made by both the architect and the builder. The architect did not take the measurements properly, and the builder followed the architect's drawing without verifying, only to discover the issue later. I believe the best solution is to replace the window with one of reduced height. Thank you again.

[Iceverge]

How much can you afford to drop the ceiling by? 

 

Lowering the steel is probably cheaper than replacing the window.

[Hemant]

Lower of the beam is not possible unfortunately as it is a mesh of beams and they are welded.