Roof Problems

[Conehead]

Sounds complicated but advise most welcome.
After last nights rain I found that the ceiling was wet in one of the rooms. On investigation outside I found that the joint between the flat roof (bad design ) and the outside wall was not sealed very well. There used to be what appears to be a rubberised paint under the white top coat which is coming off. After digging at the mortar (?) between the slab and the wall I found the joint is only about 20cm deep (into the wall) the rest is open space until it reaches the room plaster.
Also at this point the roof slab, along the wall, is slightly inside the wall meaning water running down the slab has to flow out over the joint to run down the wall. Obviously with a bad joint the water runs across the top of the wall and into the room.
The height of this joint where I have removed the mortar (?) varies from 20cm to zero at the end of the wall.

Now what I am asking:-
1- what should I pack the space between the top of the wall and the roof slab with that is water proof and does not shrink on drying (waterproof cement!!!)?
2- what should I cover the outside wall/slab joint with once packed, rubberised paint or a sheet of something?

This is a Spanish built summer house circa 1990 and I know I should of had a survey carried out when I bought but that as usual is hind sight.

Names of what to buy would be most helpful.

Pictures of the problem below. larger files available by email if somebody wants a closer look!

[Campo Kenny]

For sealing the repair I would suggest using a Spanish product called Caucho (I think spelling is right ). We had a porous patch and I was going to use another sealer called C2(cedos by Menape) Our local Spanish builder said no to that and gave me a litre of this Caucho stuff and it worked like a dream, I believe it's avalable from most builders and ferriterias.

Kenny

[peteroldracer]

Kenny - are you sure your spanish builder was not referring to the guy that built the house (badly), of which there are many out here - a Gaucho?

[Campo Kenny]

, A few of them about Peter.

[Conehead]

Thanks for the reference to Caucho, coincidentally we were in the local ferrateria and there on the doorstep was that exact named produce!

That "should" seal the wall after making the gap good but is there anything other than mortar/virtual neat cement that I can use to fill the gap with and maybe add something to try to make it waterproof. We used to use something when making the cooling water pit for casting machines but that was in the middle east.

Any ideas most welcome.

[hillybilly]

There are 2 products made by Weber that may suit: Impermeabilizante Mineral (Imper F) and Mortero Obturador (Imperstop). The latter is probably what you need. Also one made by Propamsa called Propam Tapavias which is the same as the Imperstop. Probably not cheap but both are repair mortars designed to stop serious water leaks through concrete etc.

[silver]

There used to be what appears to be a rubberised paint under the white top coat which is coming off.

That is caucho...

[toddcl]

When you finally select a compound for filling the gap put some PVA with the mix. this will slow the setting down and improve adhesion reduce shrinking along with helping prevent any damp.

It's the finest DIY material ever invented.

[Conehead]

Many thanks for all the pointers.

Hillybilly- I checked for Weber and found them to be an Argentinian company. The products you mentioned did not seem to be on their web site. The did have something for Mortero Obturador though. Any ideas where I can find the products you mentioned?

Campo Kenny/Silver- Yes you are correct having now found it locally

toddcl- Sounds a good idea! How much PVA (Polyvinyl acetates) should one mix in to the compound (ratio/spoonful or what)? Any particular supplier in Spain?

Thanks again now have to wait for rain to stop

[JAKE M]

the outside of our house was rendered in "capafino blanco" which is impermeable. it can be bought in a grey or white finish. it is applied after the rough cement/mortar and is applied in a 2 or3 mm coat.

[silver]

Ask at your local for "aditivo hidrofugo para cemento " if you want to make your concrete waterproof...but if you are thinking of using caucho..there would be no need... what you must do is wait a min of 28days for the cement to dry before applying the caucho... it probably come off because was used to soon...

[hillybilly]

Weber products are available through most builders merchants, but you will probably have to order this in. My catalogue is 2005 and they do sometimes change the names of their products.
Website address www.weber-cemarksa.es
Helpline 900352535

[Conehead]

Thanks Hillybilly, I just checked the site and you are still up-to-date. Both products are listed. My search engines only came up with the Argentinian site and I noticed the same photographs are used for a product with a different name.

Now to try to do something, besides cover the area with plastic, which has just been torn off in the high winds we are experiencing now.

Thanks again to all.

[toddcl]

Conehead

Re PVA

I use about a tea cup full mixed in a bucket of water and also paint the surface I'm applying the cement mortar to. The benefits are that the mix is easier to trowel and bonds much better.

I understand you can buy PVA in the big DIY stores down on the coast but my local ferreter'ia only has it in wood-glue form in small bottles.

[jazper]

Didn't they used to use washing up liquid before the days of PVA?

[Conehead]

Yes aready heard that one and even tried "Fairy Liquid". Was not sure it worked though!

[peteroldracer]

A diy site has this to say (other stuff too on www.axp.mdx.ac.uk/~john49/cemfaq.htm)
What is the truth about Fairy Liquid? My neighbour reckons it is a brilliant mortar plasticiser.
It gives you hands that do dishes. Fairy liquid plasticises mortar, but adversely affects its final strength and durability. Lignosulphonate type plasticisers are much better. If you wander over to http://groups.google.co.uk and interrogate it for the word "Lignosulphonate", you will probably find a previous post on the subject. You could apply a logic game type approach to this as in "If fairy liquid is so good in mortar why does anyone make a mortar plasticiser at all?" Use quality plasticiser, Febmix, Cormix and Beaver-Cementone being but three that spring to mind, though there are at least half-a-dozen. I would suggest the use of a mortar plasticiser in most cases. These are almost all lignosulphonate (sulphite lye) preparations and are "green" as they are a by-product of the paper industry, which would otherwise need treatment prior to disposal. Lime should be used for older properties mortar repair work, but unless you want a total retro house use gypsum plaster internally.
NB - No mention of PVA, although I am also one of the many that swear by it! All smoke & mirrors?

[hillybilly]

The use of PVA vs washing up liquid in mixes is certainly not the same thing!

A drop or two (no more) of washing up liquid in a concrete or mortar mix is used in place of conventional plasticisers - it traps air in the mix, making it easier to work. The downside is it makes the mix much weaker.

PVA, as outlined above, improves the workability but also the adhesion. Your local paint shop may sell large containers of PVA glue if your ferreteria doesn't stock it.

[Conehead]

Has anybody got any names for PVA that is available locally?

I have searched and come up with a few names, including P.V.A, but before making the trip to the coast some names that might be available would quickly narrow the search especially in the local ferreteria.

Many thanks.

[hillybilly]

It's called PVA or cola blanca. There are brand names such as Ceys but your best bet is to look for the shop's (ferreteria or paint shop) own brand which will be cheaper. There should be no need to go to the coast for it.