window lintel repairs - what do I do?

[johanisk]

A bit of a DIY numptie here, so be patient.

I've got an unfaced concrete and steel lintel above my window that's showing signs of cracking and a builder "friend of a friend" came round and said all it needed was for the cracks to be filled with a quick drying cement and then it should be fine. He said it was such a straightforward job that I'd be cheaper doing it myself!

I went to B&Q to get the right stuff to use and asked the staff and they didn't seem to have a clue what to give me to do it so I left empty handed.

If I can get decent advice from anywhere, this is the place!

Thanks!

Colin

 

[noseall]

If the span of the lintel and the relevance of its location within the wall are such that simple repairs are adequate then fixing it with any mortar will do.

It sounds like air and water have got to the reinforcing steel and have caused the concrete to blow. A successful repair will depend upon how well the mortar repair seals the lintel from the elements.

For best results the repair will need to be substantial enough to tolerate the weather i.e. heat cold wind and rain. It may involve chiseling away some of the lintel material and effectively rendering the front of the lintel.

 

[^woody^]

Why quick drying cement? Is the lintel going anywhere?

Whatever is used, moisture is going to penetrate from within the wall and through the rest of the concrete lintel.

Lintels can stay cracked for years with no problems, or the crack can gradually get worse. It all depends. But a repair is a temporary repair - but temporary can be many, many years. Just keep your eye on it

You could just fill with a silicone mastic, or gouge the crack and just use normal (3:1) sand /cement mortar. You can get small bags of mortar (2kg), to save buying big bags of separate sand and cement. Or get a bit of this builder friend

To blend this in afterwards, make a cement slurry and brush [paint] this on the whole lintel, and it will all dry the same colour

 

[johanisk]

thanks for the advice.

I've got the cement mortar and went to fill the cracks this morning.

I started by gouging out the loose material and quite a big chunk fell out and exposed the lintel, which looks fairly rotten with rust...

images here //www.diynot.com/network/johanisk/albums/3766

It doesn't look that good to me and I'm not sure I should still be carrying on with just filling with mortar...any input gratefully received.

Thanks

Colin

 

[cmother1]

Are you sure this is a reinforced concrete lintel? From the photos it looks like it could be a rendered over steel box, or Catnic. If the steel you've exposed is flat it most likely is. Concrete lintels usually have round re-inforcing rods.
Any of the gurus out there with experience of renovating steel lintels?