I wish to replace the flat picture window in our house with a bow window. I want to extend the floor by sistering the existing joists and extending them out 24 inches from the wall. There is one catch though, the existing joists are imbedded in the concrete wall of the foundation. Any ideas out there??

I can't picture what you mean by extending the floor. Do you mean extending it only below where the window will go? You can certainly add on from the exterior but what about above the window? You'll still have to bring the extended part back to the house. Can you clarify?

I can't picture what you mean by extending the floor. Do you mean extending it only below where the window will go? You can certainly add on from the exterior but what about above the window? You'll still have to bring the extended part back to the house. Can you clarify?
Rick in reply to your query: I intend to have the bow window constructed so it will extend out from the existing wall just enough to keep it behind the existing fascia. There will be framing below the window around 12-14 inches high, upon which the window will rest. Above the window will be framed in , sealed and insulated; to finish the exterior wall right up to and attaching to the existing soffit. Something I failed to mention earlier is that I have a crawl space below the living room floor so access to the existing floor joists is OK although a bit cramped about 40 inches head room. I don't look forward to chipping out the concrete that surrounds the esisting floor joists, I need to extend 7 of these . The concrete appears to be the full thickness of the basement wall.Regards Len

I'm not real clear on what you are referring to when you say the joists are embedded in concrete. If the existing joists or "box" beam is not visible from the outside of the house and you need to break through the foundation to expose them, then you may want to consider attaching a ledger board onto the house and run your two foot joists to a girder that sits on two footings. This will prevent you from having to hammer apart your foundation. You can connect your ledger board to the concrete by drilling holes with a hammer drill and inserting sleeve anchors or wedge anchors, you can find them at any hardware store.

It was very common in this part of Canada back in the 60's to fill the space between the floor joists where they sit on the foundation, with concrete, before the subfloor was installed. For the life of me I do not know the reasoning, but it sure causes grief, especially if you want to run a pipe for a vacu-flow exhaust, basement dryer, hose bib, etc.Common sense says that the sill ledger would keep the joists from twisting at their ends.

This design takes me out of the loop for being able to help. I just can't picture it well enough to say what I'd do... but I will move this question to Exterior Home Improvement, to see if we can get some more eyes on it.

Greetings forum users: Here is an update on my floor joist issue. I am presently installing hardwood floor in the house. There used to be carpet in the living room where this window is located. In order to bring that floor up to the level of the rest of the rooms I will need to add a layer of 3/4 inch plywood to the existing sub-floor. I stopped laying hardwood about 16 inches from the window, I used my skil saw and removed a strip of sub floor 6 inches wide by 8 ft long. This exposed the ends of the floor joi9sts where they sit on the foundation. I now had good access to the concrete poured between each joist. I rented a hammer drill and chipped out enough along one side of each joist to allow me to sister and cantlilever all 7 joists. In the spring, I will remove the first row of siding to expose the rim joist, remove it and extend the joists to support the bow window and floor extension. I am re- installing the pieces removed from the sub=floor and will then add the second layer of plywood secured with PL400 and deck screws. I will not install the last strip of flooring to allow access to the existing wall when it becomes time to remove it.