Best material to fill gap under exterior door? Mortar?
It's to late now if you have used the foam. That stuss stick to everything and is impossible to clean it out without removing the door.
Hydrolic cement hardens up so fast there's no way to mix it and get it in the bag without it setting up.
About all you could do now is rip a piece of vinyl lumber and tap it in place, that would not rot and would support the outside edge of the threshold.
With just foam under it that threshold it's going to bend and crack the caulking seam on the outside edges.
Really need to take the time and figure out why that waters getting in!!
If that type bug is getting in there there not going away until the moisture problum goes away.
To kill them get yourself some Roach Away. It's 95% boric acid.
Last edited by joecaption; 11-21-2012 at 11:21 AM.