Water penetration.

Richard9876

My wife and I are buying a house. The surveyor says most of the walls are blockwork + insulation + render (i.e. no bricks and no cavity).

I would appreciate it if anyone could answer the following questions :-

1) As the render ages and cracks is it likely that water will penetrate the walls ?

2) Roughly how many years will the render last before it needs to be refurbished ?

3) Will it be possible to refurbish the render as it is attached to insulation which presumably would be damaged if the old render was forcibly removed ?

4) Some parts of the house are old and here the walls will be blockwork + cavity + bricks + insulation + render. Are these walls likely to have any problems as regards water penetration and retention ?

Thank you for your help.

Richard

Chanes

The only thing I would be certain about is that if there is a crack, water will always find it and over time will worsen it and penetrate beyond it.

How long it last would depend on what was used, how it was rendered and how good the surface beneath it was/is.

camptownraces

Your surveyor should be pleased to answer your questions.

Phone or email him for professional advice on these issues.

Davesnave

So it's been externally insulated, and the 'older' walls are cavity construction while the 'newer' ones aren't. That sounds suspect for a start; are you sure you have that the right way round?

No one can say how long the rendering will last because:

• we don't know when it was applied
• we don't know what type it is
• we don't know how skilled the person applying it was
• we don't know if it is subject to any abnormal conditions

For example, my bungalow was rendered in 1973 and much of that is still sound, but some idiots jerry-built a conservatory in 2006 approx, and a lot of that is cracked and unsound.


External insulation would be reasonably waterproof because of the situation its placed in, just like cavity batts are foil faced to avoid any transfer of moisture. Yes, the insulation might have surface damage if the render were ever replaced, but have you seen what happens when render is stripped from common house bricks? It's probably going to be similar and not a huge issue.


The obvious person to answer your concerns is your surveyor, not some random bloke like me on the Internet. He/she is in possession of the facts and that's what you pay him/her for.

Richard9876

Thank you for your replies.

I have discussed all this with my surveyor and he says everything is fine however if there is a problem he will not have to deal with it.

I would like to hear the opinions of anyone who has had experience of walls that are blockwork + insulation + render.

The house has been substantially extended. As regards the new walls the surveyor said ;-

"Typical detail would involve the insulation being retained with corrosive resistant pins fixed to the blockwork prior to rendering."

I was only looking for an approximate lifetime for the render assuming things are average for type, skill and conditions. The render was applied approx 2012.

I would welcome any further opinions anyone has.

TBeckett100

My house is 3/4 render applied in the 60s and is still going strong. We have a blown patch (where it bubbles) and recently had that patch done but the rest of it is rock solid.

As long as your guttering is efficient, it should serve you well.

I think you are over thinking or worrying about it. Just look around for any bubbling.