Yes it’s completely random. Some areas well adhered, some the backs of the tiles have no adhesive at all. And seems really weird on a single tile you can get one half well bonded, then a crack in the screed, and on the other side no adhesion at all. They used ivc high temp adhesive, and for the bits already patched up karndean high temp adhesive (crossing the streams there are we with amtico flooring ) - that adhesive seems to work better in this setting.
Now wouldn’t it be funny if your mate in Essex who had probs with renovate is the guy who fitted this job !? When anything goes wrong like this you wish you’d asked 50 more questions of the trades installing, but realistically as a consumer I should be able to rely on pros to do their jobs correctly.
Thanks, if we end up ripping up the whole lot and going again I’ll be asking for the mapei compound that has been tested / approved for use over wunda.
There should always be damp tests before fitting. I wouldnt have fitted the product until the heating had been commissioned. I,ve had problems before in fitting with the temp in the house being too low.
Thanks. Reading everything here it sounds like the most likely cause is the cold house during the install, and even though the temp was turned up slowly you’d imagine a fair bit of moisture to be trapped given the approach, and crack. Neither the fitter nor plumber seemed remotely concerned about the temperature in the house or the wait til a later date to commission the heating. I would have expected the fitter, given he’s covered everything in levelling compound and laid the floor on top to be more thorough, but then again he turned up not even knowing what a wunda ufh system is, and how it differs from other wet ufh systems, so seems to me he was winging it.
Hi all, the solution you posted and discussed here is precisely what I’m planning to install in my 2008 built Cala Home in the Borders. In my case I’ll put the Wunda system on the chipboard subfloor, and then screed to 5mm followed by Amtico Signature planks laid in Herringbone. May I kindly ask for your overall views and advice? are you happy on balance with the outcomes? what would you do differently if you were me? many thanks Nick
The following week, the floor fitter arrived to begin installing Amtico Spacia, using small planks laid in a herringbone pattern. He started by priming the floor and applying Level It Renovate. The amount of latex required turned out to be more than double what he had expected and quoted. I accepted the additional cost, understanding that he was not very familiar with the Wunda underfloor heating (UFH) system. The design of the product meant that some channels in the boards were not filled with pipes, naturally consuming more latex. This would typically use more latex than an installation over a UFH system embedded in screed.
i have just looked over a job that requires lot install the client currently has down a new underfloor heating system made of a polystyrene channeled out for the pipes to run through , the date sheet say to lay over with instamac product , i have spoke with these and they don't like the idea , spoke with FBalls won't entertain the idea , mapei how ever will allow renovation screed to be installed , not sure wether this will , work , i was just wondering if any one else has had the same issue .
It says instarmac to be used but instarmac say they don't like the idea??? Or have a I read that wrong? I've only ever used Renovation & CL plus over these type pipe systems but at a depth of around 14mm minimum and had no issues. I've made sure I've primed the hell out of it also. The CL + has less meterage by the bag so use Renovation instead when I have one of these. Just got to make sure the boards and pipes are fully secure with no movement whatsoever and I pour in 2 separate coats.
Thanks for replying rugmunch , that’s correct instamac are recommended on the data sheet of the polystyrene insulation, but however don’t feel anything over 6mm thick will work for them , as the coats of screed get thicker the tensile Strength increases . Maybe by priming adds an extra Level of strength to the polystyrene top coat ensuring the screed dosnt blow , I seem to be getting Mixed opinions on the sub structure , Mapei renovation possibly the way to go With prime a grip 2 coats ?
These systems have so many issues. Get a fully written spec from someone before you do anything. As you’ve already experienced that’s no straight forward
Hello, I came across this thread and thought it might be a good place to start for some advice on Wunda Rapid Response 20mm Trays Over Suspended Floor before we actually start the work. We're planning to install Wunda Rapid Response 20mm UFH trays on a suspended timber floor with floorboards from the 1930s and 1960s. We'd appreciate any insights on potential issues and whether this approach could lead to costly mistakes. Key Concerns: - Levelling Challenges: The ground floor is approximately 90m², and achieving a level surface as possible before the screed is obviously critical. With up to 40mm variation in some areas, is it feasible to level this without pulling up all the floorboards which could potentially damage joists? - Zoning for Screed Application: Should we approach the leveling in smaller, zoned sections to prevent the screed from pooling in low areas and ensure an even finish? Is attempting to achieve this over a huge area on a suspended floor impossible or just costly? - Screed Weight & Flex: Using a large amount of Mapei Ultraplan Renovation Screed could add significant weight so we are trying to keep it to 8mm. As concerned too much could cause excessive flex in the suspended floor. - Floorboard Condition: Some floorboards are higher at the ends and lower in the middle. What’s the best method to address this before laying the UFH trays? - Coordination of Trades: With around three different trades involved, I'm concerned about accountability if issues arise—especially after reading stories about the persons issue with Amtico installations. Proposed Plan: to start work in April with no heating down stairs. 1. Address Structural Flex: Reinforce any joists needing additional support. Is there a best approach to this? 2. DPC Installation: Lay a DPC. 3. Plywood Layer: Install 6mm ply as per Wunda’s instructions. 4. Tray Installation: Secure trays with spray adhesive. 5. Pipework: Install UFH pipes. 6. Testing: Run the UFH for 3 days. 7. Screed Application: Apply 8mm Mapei Ultraplan Renovation Screed, primed with Mapei Eco Prim Grip. Should we consider applying the screed in smaller zones to maintain an even surface? 8. Final Flooring: Install Karndean glue-down LVT. Request for Feedback: - Does our plan seem sound, or are we overlooking potential issues? - Would zoning the screed application in smaller sections help avoid uneven distribution and pooling? - Are there specific pitfalls with suspended floors and UFH that we should prepare for? Any advice, especially from those with experience in similar projects, would be greatly appreciated!
Hi there We had an issue similar to yours only within the complexity of the weight concerns , I wouldn’t recommend I using the foil backed products as the tensile strength of the screws maybe stronger than the foil adhesion this leading to the screed blowing from the subfloor , also I would recommend getting the system up to temp prior to any screed works , make sure the flooring is laid in to a high temp adhesive, we researched into the suppliers guaranteeing the products on the foil backed insulation and no one will put this in writing .
Thank you for your reply. We plan to use spray adhesive to secure the UFH trays, as recommended by Wunda. The only component we intend to screw down is the 6mm ply, which will be laid directly onto the floorboards over a damp-proof membrane. Wunda also suggests using Mapei Ultraplan Renovation Screed with Mapei Eco Prim Grip as the primer. Are these the same products you used? Have you successfully retrofitted the trays that you’d recommend? We haven’t started any work yet, as we want to ensure we've thoroughly researched everything before committing to a particular approach or contractor.
