Attaching to existing foundations

[akist]

Hello everyone,

We are digging trenches to build foundations. The house has an underground basement and there is a wall we are extending and are digging right down that wall to find the existing foundations. We know that there is a basement there so we have to dig deeper than in other places. They dug yesterday down to what seems to be the top of the existing foundations, ie where you ordinarily start with the underground bricks. I believe they need to dig deeper to go to the bottom of the existing foundations and then pour concrete to match precisely the existing.

Am I right?

Also, are there techniques to "attach"/"connect" to the existing foundations to make sure the extension(s) do not start to move away on their own?

Many thanks

 

[trevorbayliss]

you can drill into the old foundation and glue in place rebar. I used this to join in with my new extension foundation, but kept the old conservatory foundation as it was huge. Much bigger than my new foundation. So there was little point in digging it out. We just connected you to it.

This is what BC recommended. So i assume you could connect into your current foundation in the same way.

 

[akist]

Yea they did this to join their brand new foundations that were poured in on different days, but did not do this where the new foundations join onto the old ones? Is that weird?

 

[tony1851]

If your old foundations are stepped brick footings, it would be difficult to connect them to new concrete footings. But in most cases it doesn't really matter. What does matter is that the new masonry is adequately bonded or tied to the existing wall(s) all the way up.

 

[^woody^]

You would not connect new foundations to existing ones.