'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

Wagearner

Sorry - posted twice accidentally - can a mod please remove one?

Thanks!

David_Aldred

Hi,
Minimal thickness solid walls are designed to be breathable. That is to say wind driven rain and any condensate is designed to vent outwards through the wall including both brickwork and mortar beds.

If you have rendered part of the wall this design function will be compromised. If you have rendered it with a hard dense cement render instead of a breathable lime render you will have compromised the design function even more.

Cement renders are too hard and dense for many substrates such that they crack and detach from the wall taking the face of the brickwork with it. Once cracked a cement render stays cracked allowing moisture in whereupon through freeze / thaw damage the problem spreads.

Lime renders are breathable and tend to self heal small cracks as rainwater passes over them in the same way stalagmites are formed.

If the lower areas of exposed brickwork are re-pointed in a hard dense cement mortar instead of the breathable mortar the house was built with, you will have caused a similar effect to that described above. The evaporation that used to occur through the mortar beds outwards will be !!!!!! and the bricks will become wetter. Typically the outer face of the bricks starts to degrade / break away through increased freeze / thaw damage whilst the cement mortar re-pointing remains proud.

Painting reduces evaporation outwards even if described as breathable. Some exterior paints are far more breathable than others but all retard evaporation outwards.

If the brickwork pores contain water instead of air they are colder and if they are colder they are more prone to condensation within them which is a downward spiral of dampness.

From the above it may be seen that even if you stop moisture coming inwards you will retard evaporation outwards and condensation within the depth of the wall will go up such that you will create a moisture resevoir within the wall able to sustain dampness.

The sun shining upon such a wall can drive such condensation and any penetrating dampness inwards if it cannot readily vent outwards.

External paint and coating manufacturers often make stupid claims of 'this will stop all damp' which is complete nonsense and in view of the above can actually make the problem considerably worse depending upon the construction and exposure of the property in addition to the lifestyle of the occupants.

I have come across a well known manufacturer who was in deep poo when the inside of a solid one brick thick outer wall house went damp from top to bottom on every outside wall with failing damp internal plaster / decorations directly correlating to the external application of their coating they described as breathable and a cure for all damp. Apply it if you want but it will be entirely at your own risk.

If the rooms are cold then internal insulation dry linings with appropriate and fully effective vapour barriers may be worth considering and discussiung with manufacturer's.

Hope this helps, kindest regards David Aldred Independent damp and timber surveyor