Victorian Solid walls and concrete render

magice

Hey all...

There is so much conflicting information online about the effects of concrete render on Victorian properties. The overriding opinion currently seems to be that Victorian solid wall properties require lime based render on the outside and inside walls to allow the brick work to properly breathe. This all sounds logical and makes sense, and if correct then the past 60ish years have involved lots of old houses having concrete render/unsuitable plaster/non breathable paint put all over these properties. But there must be tons of solid wall houses with concrete render out there that are still standing and not facing major issues.

Given that, I wondered what other Victorian/solid wall homeowners had experienced with this, e.g:

• Major issues from concrete render and have had to completely hack back and render in lime-based materials
• No issues with concrete render, house all good
• Found external concrete OK if internal walls use lime based plaster/render

I also wondered - if the concrete render was good and waterproof, bricks underneath shouldn't get wet internally anyway, it's only if it starts to crack and deteriorate and nothing is done about it?

Doozergirl

I've spent 20 years renovating old houses. All house behave differently because they're all subject to different conditions and levels of maintenance.   So I've experienced most of those things.  

If it isn't broke, don't fix it is my view, but if there are issues then you seriously need to take a look at why and really consider using original materials when rectifying issues. 

Older house were designed to breathe.  Moisture is created inside as well
as out and lime mortar usually acts to draw moisture out from the inside of the house, that is why concrete render doesn't help.  People think they're protecting from the elements but it's actually a two way process and the render is blocking moisture from getting out too.  

magice

Nice one! What is the ideal render plaster for indoors? A lime based one? Could having concrete on outside and lime on inside help to an extent, as long as you had a good way to ventilate to let the moisture back out?

FaceHead

I live in a Victorian (c.1890, solid double brick walls) terrace with concrete render on the front. On the inside is insulated plasterboards dot-dabbed onto what appears to be a gypsum plaster (or perhaps older lime plaster skimmed over serval times with gypsum), so basically we're breaking all the rules.

None of this causes any issues, other than the external render being less attractive than the houses on the street that have the original facing brickwork. 

aoleks

why the need to render the outside? as someone who was planning the same a short while back, I can tell you painting the bricks looks better, doesn't hide any potential defects, costs £60 for a 3 bed house and doesn't create any problems with breathability.

magice

FaceHead said:

I live in a Victorian (c.1890, solid double brick walls) terrace with concrete render on the front. On the inside is insulated plasterboards dot-dabbed onto what appears to be a gypsum plaster (or perhaps older lime plaster skimmed over serval times with gypsum), so basically we're breaking all the rules.

None of this causes any issues, other than the external render being less attractive than the houses on the street that have the original facing brickwork. 

Good viewpoint! Has it been like that for a long time/before you lived there? No damp issues anywhere? What is the vintilation like in the house?

magice

aoleks said:

why the need to render the outside? as someone who was planning the same a short while back, I can tell you painting the bricks looks better, doesn't hide any potential defects, costs £60 for a 3 bed house and doesn't create any problems with breathability.

Agree with you! Though most instances will be where the owner has 'inherited' a rendered property that has been so since way before they moved in. Still though, don't you need to be careful painting brickwork with new masonry paint as they can have the same effect as concrete render in that it won't let the house/bricks breathe when they have moisture trapped in them?

Mistral001

Victorian houses were usually built with several coal fireplaces which provided heat and ventilation.  They also had drafty windows and doors.  Hence any damp penetration through walls from outside to inside usually quickly evapourated and taken away up the flues and out the drafty windows and doors.  If some moisture did not evapourate, then the different standards of the day meant that it was tolerated. 

Using lime mortar is a bit like wearing a heavy woolen overcoat.  It will breath in both directions, so you will generally not get condensation on the inside, but in the rain it will let in water eventually.  If you seal the outside with render, it is a bit like a waterproof coat. You will be able to stop water coming in from the outside but you will get condensation on the inside as it cannot breath through the material..

PS the waterproof raincoat with large vents like those worn by private eyes in 1950's movies are probably the a good compromise.  That provide a means to keep the water out and provide permanent ventilation to stop condenssation.

magice

Mistral001 said:

PS the waterproof raincoat with large vents like those worn by private eyes in 1950's movies are probably the a good compromise. 

Haha nicely put. 

Agree with all your points. Sounds like a concrete render in a house that has decent enough ventilation could work then?

maisie_cat

We have a c1900 stone cottage with some damp issues caused by cement/gypsum products.
The stone was pointed and partially rendered with cement mortar at some point, we have prevailing sea winds and moisture gets trapped. Luckily it's working loose and I have removed a portion of it, I'm going to remove it all and redo with lime this year.
In some places the hardness of the mortar pointing compared to lime has cracked some of the stones
The internal lime plaster has been replaced/overlaid in places with gypsum and painted with acrylic and in one place gloss paint! Where moisture gets through the 600mm wall we have blown elements and paint blisters that we will have to deal with at some point.
We think the work was done in 2002, and there is evidence of repeated efforts to cover or fix "damp issues" since then.
Ours is probably made worse because we are near the sea in a windy position, although the glorious views and sunsets more than make up for a bit of damp.

FaceHead

magice said:

FaceHead said:

I live in a Victorian (c.1890, solid double brick walls) terrace with concrete render on the front. On the inside is insulated plasterboards dot-dabbed onto what appears to be a gypsum plaster (or perhaps older lime plaster skimmed over serval times with gypsum), so basically we're breaking all the rules.

None of this causes any issues, other than the external render being less attractive than the houses on the street that have the original facing brickwork. 

Good viewpoint! Has it been like that for a long time/before you lived there? No damp issues anywhere? What is the vintilation like in the house?

Ventilation is broadly good, which I suppose is what's keeping us afloat. Both upstairs and downstairs front rooms have fireplaces in (one decorative and loosely blocked + airbrick and one in use as a wood burner). The windows have trickle vents, but we don't actually find they are required much.

The concrete render on the outside has been around a while (predates google street view in 2007, but I would guess it was done in the '70s). The plasterboard on the inside is a 2 year old addition, but before that it was at least skimmed over with gypsum, probably for at least a couple of decades.