'Protec' External Wall Coating

Wagearner

Has anybody heard of "Protec" - supposedly a system to cover external walls or renders as a more durable alternative to paint?

My house is a solid wall brick construction around 100 years old, with the upstairs walls rendered and painted and the brick exposed on the ground floor. One room at the rear of the house (with three large external walls) is particularly cold and slightly damp. I think the damp is mostly condensation on the inside, but paint the exterior wall is starting to discolour and peel. I will need to repaint at least this wall and therefore the whole rendered area.

The original contact with the Protec company suggested that excluding penetrating water with their system would improve insultation by keeping more dry air trapped in the bricks. I can't imagine the U value will improve, but anything to help would be a massive improvement!

The downstairs exposed brick is also very soft and soaks up water like a quality kitchen roll. My neighbours (the other half of the semi) had their wall treated with a sealant of some sort last year and have noticed an improvement in the brick strength and insulation.

I have a representative coming to quote for the application this week.

Does anyone have any experience of this or similar applications? The company has been around for some time, but it's not an area I've ever had any experience in before.

Otherwise, has anyone ever had external insulated render applied? This would seem the ideal solution for the upstairs and possibly the whole rear/sides of the house, but I'm assuming it's a little £££!

Any help would be massively appreciated

David_Aldred

Hi,
Minimal thickness one brick thick solid walls are designed to vent outwards any penetrating dampness and condensation. In other words they are meant to be breathable.

Alterations over the years albeit done with the best of intentions alters this design function. Applying render reduces evaporation outwards, applying paints reduces evaporation outwards and so does re-pointing the original breathable mortar with a hard dense cement mortar.

Lime renders and mortars are breathable and when they crack they tend to self heal small cracks as rainwater washes over them in the same way stalagmites are formed. This does not happen with hard dense cement renders / mortars and once cracked they stay cracked.

Water gets behind the cement mortar / render and through freeze / thaw action blows off usually taking the face of the brick with it.

If you reduce evaporation outwards then moisture such as condensation within the depth of the wall will increase. If the pores contain water instead of air it will be colder and more prone to condensation such that a moisture resevoir accumulates able to sustain such dampness.

Typically the outer wall coating is not perfect so penetrating dampness continues to get in to some degree but cannot vent outwards easily.

All paints / coatings reduce evaporation outwards to some degree and this varies considerably depending upon product.

If the sun shines upon a solid wall that has dampness within it and that dampness cannot vent easily outwards then the sun will drive that moisture inwards.

Be very mindful of just how wet a wall can get through interstitial condensation alone. That is to say not just condensation upon surfaces but actually within the fabric of the wall itself especially if you have warm moist air at a decent temperature inside and it is freezing outside and you have external coatings that will not allow moisture to vent outwards from that wall.

Manufacturers will make claims of their paints / coatings curing all damp which is complete nonsense. They may be an appropriate coating to some types of wall construction but this varies very much on the construction of the outside walls, the exposure of the property and indeed the lifestyle of the occupants with respect to heating / ventilation and insulation.

A primary example I recently dealt with was an elderly lady in a solid one brick thick detached house who read the sales blurb and had all outside walls painted externally with a paint described to cure all damp. What followed was a dramatic increase in dampness to all external walls with degraded plaster and decorations - ooops.

You can put it on if you want to but it will be entirely at your own risk. If you are after improvements to insulation then pehaps consider internal insulated dry linings with appropriate vapour barriers that are fully effective.

Have a think about how that wall was originally built and what has changed - is the render breathable, are the mortar beds breathable, are any coatings clear or otherwise vapour permeable?

Not exhaustive list of what can happen by any means but hope it helps a little when you are considering what is occurring and what may occur as you alter the construction of the solid wall. Please be aware the drying down rate under good conditions is only around 25mm wall thickness per calender month so a one brick thick wall that is damp may take around a year to dry down when a moisture source is resolved.

Kindest regards, David Aldred Independent damp and timber surveyor

knowloads

Wow Dave very comprehensive. I agree and feel that a lime based render would be better like decopierre or K-rend. Never ceases to amaze me how these coating co's expect to dry walls by adding an external coat of microporous paint. (never that porous eh?) Protech are very expensive too