Expanding PU foam

[lowster]

Will bog standard (diy) expanding PU foam cause a bridge for water if I put it in a cavity? I have looked online and it appears to be an open cell structure which is porous. Has anyone had any experience with this? I wanted to use it as a cavity closer around my door and on the cavity between blue bricks and flooring concrete - where I have removed bricks from under a window to fit the door...

 

[BigIan]

The expanding foam can cause lots of issues, put to much in and your wall could belly out and yes it can act as a bridge for moisture to penetrate, you would be better off using a propriatary cavity closer system.

 

[Gazman16]

As a window fitter I hate cavity closers they sell, They are loose giving nothing to fix to and can cause plaster to crack in the long run (especially with movement caused by large doors and windows).

When I do a knock through I silicone a length of dpc to the inside of the outer brick course, Put in a small block of wood for fixing the door (only if Im not going to be able to get a fixing at an angle) And then fill with expanding foam.

This was the way I was shown to do it 20 years ago (before cavity closers?) and have never had a problem or call back.