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Basement UFH and Screed


Thorfun

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I had a few spare minutes on this lovely sunny Sunday evening and decided to spend it writing up a blog post for our basement UFH install and screed.

 

We have a 250mm reinforced concrete slab sitting on top of 200mm EPS300 in the basement. The slab wasn’t very flat and so we decided to use a cement based liquid screed to give us a nice level base for our finished flooring. So we put down 25mm of PIR to level things out and also to allow the UFH pipes to be stapled to. I did some quick maths and I figured out that it was cheaper to use the 25mm PIR and UFH pipe staples than to use pipe clips fastened to the slab and a thicker layer of liquid screed and so an order was placed with our BM and it was delivered and fitted by my lovely wife and me. We found this is a pretty easy task to be honest and only found we had to put a small bit of sand blinding to level a couple of dips in one room. In the rest of the basement the PIR just took the bumps of the slab out. We taped the joints and foamed around the edges for a belt and braces approach even though there was a DPM going on top.

 

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Next came the DPM layer. We found this a bit of a pain to do! Not hard but trying to smooth it out and keep it square so that a constant amount was taken up the walls was just fiddly. In the end we got the laser level out and set it about 150mm above screed finished level and then used that to ensure we had enough DPM up the walls. Then we had to tape it to the walls but soon found that standard gaffa didn’t stick to the concrete walls nor the dense concrete blocks! We painted the concrete with a PVA mixture and that helped a lot for that but just didn’t work on the concrete blocks at all. Off to Google and this awesome forum and I eventually found Gorilla Tape which sticks well to concrete blocks and we were off and running!

 

Following this we laid the UFH pipes. This was a job we actually really enjoyed. It was very satisfying creating those wonderful spiral shapes. We made some spacers and I was laying the pipe according to the layout designed by Wunda and my wife was walking behind with the stapler ‘kerchunking’ down the staples as we went. At the end it looked so good we were sad to think all our hard work would be covered up and never to be seen again.

 

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This was my first time running UFH pipes and also my first manifold fitting and I was very happy with how the manifold turned out. I filled the pipes with water and the pressure gauge showed that there were no leaks. That and the fact there water wasn’t pissing out anywhere!

 

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With the liquid screed booked in we needed to get a move on and get everything finished off and ready. The last stretch was to fit the temperature probes, perimeter expansion strip and create the expansion joints for crack mitigation at the doorways. Thanks to advice from this forum’s users I ran the temperature probes in UFH pipe with the end crimped down so as to not allow screed in just in case they need replacing in the future.

 

I got the expansion strip from uHeat on eBay. It came with a plastic skirt  and adhesive already attached so it was a real breeze to fit. Not much more to say about that

 

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The final thing was crack mitigation strips for between the doorways. After speaking to the screeder I decided to use 5.5mm plywood board. It was an inexpensive and simple solution. I was asked to cut them to size but leave them to the side of the doorways and the screeders would add them as they went around. Obviously I had to put them in place first to ensure I got the sizes right!

 

So here are photos of our basement ready for the liquid screeders.

 

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On the day of the screed they turned up early before the screed lorry to setup their pump and check on my prep work. They said it was exemplary and that I wouldn’t believe the state of the prep work of some of the jobs they turned up to! They had absolutely nothing to do to the prep work which made them happy and made me happy that all our hard work was worth it. They put down their little tripod level thingies and waited for the screed to turn up. Once it did it was really quick work and very impressive. If it wasn’t for the fact that they ordered 6.4m3 of screed but the company only sent 6m3 they’d have been done in a few hours but, as it was, they ended up having to wait a good 2 or 3 hours for the last little bit of screed to turn up. They were not happy as, in the end, they had to spend the whole day here when they could’ve been on to the next job.

 

But, at the end of the day we had a wonderfully flat looking basement floor.

 

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And 48hrs later we were walking on it. 🙂

 

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All in all very happy with the whole process and I will be getting these guys back in to do our ground floor screed.

 

thanks for reading.

Edited by Thorfun

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