Architectural Detailing FAQ

Franco Finishes has been trading for 18 years and our technical staff can offer advice on architectural drawings, including detailing, relevant products, U-values and colour schemes. Trouble-shooting and written technical reports can also be supplied.

Is it OK to render onto high suction blocks like Thermolite or Duroc blocks?

What considerations are there when rendering smooth concrete?

What render should I apply to ply and metal lath?

I would like to use polished plaster in a shower area. Is this recommended?

Can I have a perfectly smooth pigmented stucco with even colour?

How much do your products cost?

Do you apply your products yourselves?

Do you have BBA certificate?

Do resin based coatings last as well as cementitious finishes?

What is the difference between a normal sand and cement render and a factory made polymer render?

Is it OK to render below the DPC?

Where should I put expansion joints when using render or stucco?

Can we apply your finishes over GRP?

Are anti-graffiti coatings compatible with your finishes and does it change the surface?

Is Franco's Portofino cheaper than the top selling competitor's product?

Is it OK to render over paint?

Is it OK to render over gypsum plaster?

What maintenance is required for self coloured finishes?

What beads are used when rendering?

What thickness of external wall insulation is required to achieve 45'U' value?

You say that you give "independent technical consultancy". How can I believe that when you also market your own products?

[Franco Home]

Q: Is it OK to render onto high suction blocks like Thermolite or Duroc blocks?
A:

 

Yes, but a 3mm Universal key coat must first be applied to kill the suction. If render were to be applied directly, the water in the mix would be drawn out too quickly allowing the cement to dehydrate, giving the render insufficient time to harden and consequently resulting in poor adhesion and a powdery, weak surface.
Q: What considerations are there when rendering smooth concrete?
A:

 

All concrete will have mould and oil deposits on the surface. This should be removed with a mild detergent. Franco Universal and LP Hardener should be mixed together and applied between 2 to 3 mm and allowed to cure for 2 days, This is an excellent preparation for render, but be careful not to apply a finishing render coat greater than 10 mm thick.
Q: What render should I apply to ply and metal lath?
A: None. All traditional renders will crack on this substrate, but in the old days it would be painted.  Now we only apply renders to BluClad which is a calcium silicate board; it is a very stable board and fixing is straightforward.
Q: I would like to use polished plaster in a shower area. Is this recommended?
A:

 

We have applied our Portofino finish in bathrooms and shower areas, but it should not be applied to gypsum plaster and plasterboard. Use Cape BluClad board coated with Franco Universal/ Bloomsbury Fine /Portofino.
Q: Can I have a perfectly smooth pigmented stucco with even colour?
A:

 

There will always be some tonal variation across the surface. This occurs as the trowel edge runs across the surface and it slightly separates the pigment from the cement particles leaving two slightly different colours. But it does give the look and feel of a natural finish. If you want to avoid colour variation, it is necessary to scrape the surface to remove the laitance (*) from the surface, although this will result in the surface having a slight texture.  (*Laitance - the fatty particles which float to the surface of a plaster when it is trowelled up.)
Q: How much do your products cost?
A: It depends on how big your project is. For over 200 square metres, the prices start at around £22 to £25 per square metre supply and fix for Natural stucco. If you are using our Portofino Italian style stucco with a metallic finish it will cost from £50 to £65 per square metre.
Q: Do you apply your products yourselves?
A: We will guide you to our recommended contractors who have experienced staff trained in the application of our products. We do not recommend the use of untrained contractors in the application of specialist finishes.
Q: Do you have BBA certificate?
A: No.  It costs between £8,000 - £10,000 per product to gain certification.  With nine products in production, we don't believe it makes business sense for us at this time to gain certification.  The downside is that some local authority work is difficult to bid for without certification.  

The certificate is based on tests completed on a weather rig over a 2 week cycle.  This process certainly gives a strong indication of adhesion and weather permeability - albeit under perfect application conditions and perfectly in line with the manufacturer's specification.  However, we all know that perfect conditions are often not achieved in reality - which is why Franco manufactures products which will tolerate a degree of abuse.  In any event, we only recommend plastering firms who are trained in the application of our products.

Q: Do resin based coatings last as well as cementitious finishes?
A: No.  There are many different types of resin coatings - or polymer emulsion, as they are more commonly known.  These types of coatings will normally last 10/15/20 years depending on the quality and whether it is correctly installed.  After this period of time, the finish will have lost its elasticity, become brittle, and it will also have lost some of its adhesion; therefore failure is likely to occur.  [The price of thin resin coating will vary from £25 to £95 per 15/20 litre tub.  Basically, the more you pay, the better quality of product you'll obtain.]

Cementitious finishes are far more stable.  They will last from 25 to 50 years, as long as each coat is the right strength, has been correctly mixed, applied under good conditions, allowed to cure and been protected during its early life.

Q: What is the difference between a normal sand and cement render and a factory made polymer render?
A: In a word - performance.  Rendering was always the cheap way to finish a building.  Unlike bricks, which were pre-made in quality controlled factory conditions, renders were made on site by all sorts of different people in variable conditions.  Under the circumstances render got a bad name.  [We could go on at length with the answer to this question, but it would take too long.]

Basically, the polymers in factory made renders give consistency and control of what is a powder material.  All the applicator has to do is add water and machine mix.  It is far easier than with normal sand/cement render to spot  any misuse on site (not in line with the manufacturer's recommendations).

Q: Is it OK to render below the DPC?
A: All manufacturers will advise against this.  Due to water ingress and frost action, most renders would fail within 5 years.  However, the desired effect can be achieved by introducing BluClad - a calcium silicate board - fixed to the substrate.  This isolates the moisture from the render coat.  A suitable coating (can be provided by Franco) must be applied to the board for a successful specification.
Q: Where should I put expansion joints when using render or stucco?
A: The first expansion joint should be positioned in line with the substrate expansion joints, typically every 6 linear metres.  In the Code of Practice for external render, expansion joints are also put to one side of window and door openings: stress cracking tends to occur here, making it the weakest part of the render matrix.  Be sure not to render an unbroken area larger than 18 square metres.
Q: Can we apply your finishes over GRP?
A: With thin coat stuccos which are correctly formulated for the job - you can.
Q: Are anti-graffiti coatings compatible with your finishes and does it change the surface?
A: There are many types of anti-graffiti coatings.  Typical are those which are classified as sacrificial anti-graffiti coatings - which will last one time and then have to be over-coated once attacked. These affect the surface finish least of all.  Recently, we have been using a water wax coating which we have found to be the best.  Others which will withstand repeated attack and cleaning will create a glazed surface.

All of these coatings are compatible with our finishes.

Q: Is Franco's Portofino cheaper than the top selling competitor's product?
A: Oh, it's a tough commercial world.  Ask us to quote and you're unlikely to be disappointed.
Q: Is it OK to render over paint?
A: We strongly advise against it.  You should only consider doing so if you bush hammer or needle gun the painted surfaces beforehand.  (We are aware that some companies put a fairing coat over the paint when the new finish is a resin type coating.  We remain to be convinced.)
Q: Is it OK to render over gypsum plaster?
A: No.  Gypsum is too weak a background to apply a cement product over.  (It is likely that the cement will pull it off.)
Q: What maintenance is required for self coloured finishes?
A: A jet wash with a mild detergent is sufficient to clean most atmospheric deposits.
Q: What beads are used when rendering?
A: All external render, stuccos and thin coat finishes will have to have stainless steel bead.  in the case of natural stone stuccos, it is best to use timber rules to form the external angle in the render.
Q: What thickness of external wall insulation is required to achieve 45'U' value?
A: In a low thermal value substrate such as concrete construction of 225mm thickness, the minimum will be 60mm of insulation plus 10mm of render.
Q: You say that you give "independent technical consultancy".  How can I believe that when you also market your own products?
A: Franco's policy is genuinely to discuss applicability of its own products and other manufacturers' products to clients' requirements in an open and constructive manner.  We find that this enables clear understanding and objectivity prior to specifying.  If a competitor's product is more appropriate for your requirements than ours, we will say so up front.  (We don't want to take on business if we suspect the client will not be happy with the end result).  If competing products are comparable, we will be happy to give our view on the pros and cons.  Quite often, where products from competing manufacturers are comparable, we find that when we are specified, our client's decision was based either on price, on ability/willingness to take a flexible/customised approach, or on the added value that we bring with our technical expertise. (With Franco Finishes, you deal with practitioners, not with salesmen.)

If requested, we are prepared to take on specific fee paid consultancy assignments on the clear understanding that our products will not be specified.


Franco Finishes Limited

Disclaimer: The answers to the questions posed are offered in good faith based on the general experience of Franco.  For each project, specific professional advice should always be sought in order to take into account the particular context, conditions and materials unique to the project.  Franco Finishes accepts no liability for any adverse consequences incurred through following the advice above.