Sealing under my UPVC door sills

DennisTenus

Hello,

I had my UPVC doors and windows installed at least 10 years ago. Recently noticed some black in the corners inside which is probably mould/moisture getting in so had a look outside and noticed they haven't sealed under the sills of any of the doors. They sealed down the sides of the doors.

I assume they should be? I intend to buy some good external UPVC sealant and do it myself - is this best thing to do?

Should I only seal around it and underneath (blue lines and arrow) not where I have put the red line?

tony6403

The windows sit on the outer leaf of the cavity wall and I don't think that applying sealant will make any difference.
Applying it along the red line will definitely be of no use.

Ruski

Do not seal along red line as that is where drainage occurs from the inner frame.

Sealing the sill to the floor is best done on the inside only, as again this assists with drainage.

HTH

Russ