Cable through foundation?

[Peter500]

I'm doing an extension and need to get an armoured cable through the foundation and want to know the best way to do it. The main question is around how I should build the foundation.

Would I need a lintel for the cable or can I just drill a whole in the trench blocks?

I am also considering putting it in a conduit but I'm not sure that there would be much benefit. One end will come up through my extension floor (which is fine) but the other end will be running outside to my existing garage, so it would probably run down the outside wall and then underground. Do conduits have some kind of termination so that they don't fill with dirt?

 

[Simon35]

Run it in twinwall ducting, for the full underground run. You can bring the ducting up into the extension floor and cut it off flush once the concrete has gone off.

 

[Peter500]

Run it in twinwall ducting, for the full underground run. You can bring the ducting up into the extension floor and cut it off flush once the concrete has gone off.

Do you know how I would terminate it at the other end? It'll come out of the ground. Twinwall ducting would then be a bit big/unsightly to run up the outside wall. I also don't want to be digging up the floor in my existing garage.

 

[Simon35]

Do you know how I would terminate it at the other end? It'll come out of the ground. Twinwall ducting would then be a bit big/unsightly to run up the outside wall. I also don't want to be digging up the floor in my existing garage.

Cut the twinwall off below ground level, seal it with expanding foam and bring the cable out of the ground and up the wall, if I've understood you correctly.

 

[SUNRAY]

Cut the twinwall off below ground level, seal it with expanding foam and bring the cable out of the ground and up the wall, if I've understood you correctly.

Expanding foam outdoors... Are you sure???

I assumed by now everyone would have discovered what happens to the stuff and not advocate its use in such a situation.

 

[JohnW2]

Expanding foam outdoors... Are you sure??? ... I assumed by now everyone would have discovered what happens to the stuff and not advocate its use in such a situation.

Below ground level? I know what happens to many PU foams if exposed to sunlight outdoors for long periods, but I've personally never seen anything happening to it otherwise, including 'underground'.

Kind Regards, John

 

[JohnD]

I think I've had some that absorbed water and was useless.

 

[JohnW2]

I think I've had some that absorbed water and was useless.

Foams do vary. However, if you're suggesting that some 'closed cell' PU foams can 'absorb water', then a good few sailors would presumably be very unhappy about their lives being put at risk every time they take to the water, wouldn't they?!

Kind Regards, John

 

[SUNRAY]

I have had to remove the disgusting slimy/smelly residue on many occassions and many building sites now require a written assessment for each and every application of expanding foam for this reason.

Underground/in contact with mud is crazy, the chemical reaction breaks it down very quickly.

 

[Simon35]

Expanding foam outdoors... Are you sure???

I assumed by now everyone would have discovered what happens to the stuff and not advocate its use in such a situation.

Closed cell foam will perform perfectly well in such a situation.

 

[SUNRAY]

Closed cell foam will perform perfectly well in such a situation.

And I assume you have gone back to these installations 5 years later and wondered why it's gone orange?

 

[JohnW2]

And I assume you have gone back to these installations 5 years later and wondered why it's gone orange?

Orange is, at least in my experience, what happens to some PU foams after exposure to UV/sunlight - and, even then, the discolouring, per se, does no harm. As both Simon and myself have said, closed-cell foam should be fine in the situation described, just as it is fine when constantly exposed to sea water etc.

I recently exposed some PU foam that had been in enclosed/inaccessible (albeit dry) places for 30+ years, and it was not even significantly discoloured.

Kind Regards, John