I am replacing my old front door with a prehung steel door. Currently I have a concrete sill which wraps right from the inside of the door to the outside and around the brick. In winter, this sill is a fantastic transferrer of heat, and I always wind up with condensation and mould on the inside edge of the sill. It looks like a massive undertaking to replace the whole sill, and my new door frame and sill will fit into the opening with merely grinding down the 'hump' on the cement sill. My best idea at the moment is to cut a trench in the cement sill underneath where the new wood/aluminium sill will rest and fill it with spray insulation as a thermal break. Just wondering if there is another common solution to this, and looking for thoughts and opinions on my plan.
Cement door sill
- Thread starter goser
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Help Support House Repair Talk:
GregC
Quick Belt System
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Hello, I have done only a few of this in all my time but I did just that. I Ground down the hump to flatten it out. I then used adhesive caulk down on concrete, applied foam "sill seal" and then set the new door in another bead of caulk. Finishing with small bead of caulk inside and out. Has worked fine for me in the past. Shouldn't be a problem. I have installed several patio and entry doors the same way on basement slabs or garage slabs and they all seem to be fine. Use the "sill seal" along with your foam or caulk. Be sure you use a DAP low expanding foam or others will tend to heave the door sill. 
Good Luck, Greg
Good Luck, Greg
