Expert: Bill-C - 10/6/2007

Question
QUESTION: I recently relocated to Copenhagen from Florida. The homes and commercial buildings are built of brick, typically two layers with an insulation space between the two walls. Since the homes aer typically 50+ yrs old, there has been a movement to fix mortar fatigue and draftiness by overlaying the exterior brick walls with a cementious/stucco mix, handle trowel and very laborious and costly. My Question, I am researching different methods to spray on a cementious mix over the fatiguing mortar and brick exterior, what woud be the best method to do so and the cost effective one? Utilizing a stucco sprayer & utilizing a 1 coat mix, or 2 coats - 1st a thick scratch coat and 2nd with a finish coat in varying textures? What would you suggest, my intention is to JV with a mason and start a company doing these repair work overlays. Good day and Thank You (Tak), Alex .

ANSWER: Alex,

There are various products you can use for render coat systems and its to find the one that suits its background substrate and enviroment.
From what your describing as mortar fatigue ,it is best to cure this than overcoat this purely to the fact that something is obviously wrong with the mortar design mix in the first instance, and raking out and pointing exercise would be the first course of remedial exercise for cost efficiency and if overcoated may end up with problematic cracking out with your control but of which you would be liable for.
Most overcoats in the UK are hand done but spray machines of the ones you describe are used but not efficiently due to tradesman operator / weather conditions / temperature etc..Mainly a specialist licensed company.Always and ever finished by hand.
Normal procedure for coating if not previously constructed to receive a coating system would be substrate cleaning removing laitance and remedial repair.Followed by propriety primer sealer, wire lathe fixing,movement / expansion joint forming scratch coat and finished render or roughcasting coat .Hope this is of some help as I said all methods of applying materials depend on the individual product and advice and application should be strictly adhered to on manufacturers reccomendations.If I can be of any further assistance then please enquire.

Regard's
Bill

---------- FOLLOW-UP ----------

QUESTION: thank you for that, follow up Q- The masons here are typically applying the mortar/stucco mix right over the brick, a thin layer, where you can still see the brick outline.  With more expensive applications a second applied so a smooth facade is represented. No lathing or other materials are applied on top of the brick. I do not know about chemical applications on the brick for bonding purposes, however, I do know the lathing is not applied. Does this type of application seem correct and for what purpose are they doing it this way. Since the wather here in Copenhagen is similar ot UK I imagine the reasons must be similar? Thank you..Alex

Answer
Alex ,

Are they using a cement /sand mortar for the render coat or a polymer resin from tubs ready mixed.
If you could identify the product i could be more specific in my answer.
If you could find out some history of this product ie how long has it been used and if they are any problems later on with it.
If they are applying the material directly to the brick walling then they must be using a basecoat primer of some sort or they maybe raking out the beds and joints to provide a key for the bonding of the material.
The way you are describing the layer and you can still see the underlying appearance of the brick it sounds to me its a low budget repair and is it on social housing ? rented accommodation?

Regard's
Bill