Repairs to a balcony

[Bob Minchin]

I'm visiting a friend in France in a couple of weeks time. I normally help him with a few DIY jobs in return for a cheap holiday. This years project is to effect some repairs to his concrete balcony which apperas to be cantilevered off the side of his house. it is about

8 foot wide and supported on piers underneath about every 15-20 feet. The problem is the top surface is delaminating, letting water in in the winter and we think corroding the steel reinforcing mesh thus lifting the skin more and so on. He wants to tile the top surface in an attempt to shed the water - which I think this will work but the questions are:- 1) how to treat the reinforcing steel against further rust - all the rust neutralisation products I know of are basically phosphoric acid and will attack the contrete too! 2) how to get a thin layer of new concrete to bond onto the old substrate to give good enough adhesion so the tiles don't lift in a few years time.

Our combined french is not good enough to describe the intricacies of the problem in a builders merchant.

I'm wondering if the problem has not penetrated too deeply, whether a thick bed tile adhesive would be the right way to go to build up the surface at the same time as fix the tiles.

What does the team think?

TIA

Bob

[Andrew Gabriel]

This is a problem which is affecting many 1950's and 1960's concrete structures. I don't know how they are fixed but I've seen some that have been. I've noticed that whilst the more expensive things like motorway bridges get fixed, cheaper things such as the Concrete Utilities lamp posts don't, so it may be that the cost of proper structural fixing is not cheap. A google search turns up a number of articles, but I would be weary of some of the suggestions of sealing the concrete, as that is probably more likely to seal moisture in than it is to prevent entry. However, sealing the top exposed surface probably makes sense, as long at moisture can escape though other surfaces. I've no direct experience of fixing this though; just thinking out loud.

[Mogga]

Digital camera and printer?

[Owain]

Treat it as a flat roof and tar and felt it, then put decking over the top?

Owain

[Bob Minchin]

A lateral though certainly but in the lattitudes of central southern France, I think the tar/felt would soon melt away. 35C is not unusual for long periods in the summer.

[PeterK]

SBR as an additive came to mind and a Google search turned up these specialists in concrete repair products:

[Robin]

I am sorry to chip in when I have nothing helpful to contribute to the answer but I felt moved to ask what is below the balcony, and how far below? That seemed to me likely to influence how much it is worth spending/how sure you need to be that something works. (I do of course appreciate there may be other relevant factors - eg life insurance policies.)

[Bob Minchin]

Hi Robin, It is a first floor balcony and in common with many French properties all the living accomodation is on the first floor. The balcony is used for nearly all meals other than in the winter and is a well used part of the living space - possibly 200 sq ft. Not doing a repair is not an option.

Bob

[Bob Minchin]

Thanks peter I'll give them a look.

Bob

[Cicero]

================================== Bonding new concrete to old can be done by 'grouting off'. This entails making a slurry of water and cement (consistency of milk) and pouring it onto the old concrete. Help it to work in with a stiff brush if necessary and leave the surface visibly wet with a surplus of the slurry. Fill immediately with a wet mix of your new concrete (you should see the slurry running as the new concrete is added) and level off.

Cic.

[Bob Minchin]

Thanks Cic, That sounds like a very good idea.

Cheers

Bob