Deck repair question

[steplift20]

before you start cutting make sure you know what to do
i think you should get a router and cut the top layer away and replace it with good wood then fiber glass it in but how big of an area are we talking about

[bcurling]

The soft area is about 18" X 26". I do know that the floor is of 3/4" plywood with a layer of FB. I do not know what type or weight the FB is. Then above that is of course the painted surface. I suppose I could easily drill out a 2" inspection hole and with a mirror and light examine the area first. I appreciate your impute. Oh, and BTW, it appears that this soft spot was caused by the former owner installing a seat base and when placing the hold down screws did not use an type of sealant 5200, silicone, bubblegum or whatever with the screws.