My Journey into Retrofitting Underfloor Heating

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The upstairs, where we are laying the pipe on top of the floor we are using the following system


  • 16mm Overfloor Board Fact Sheet.pdf
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The boards are simply screwed down they can also be glued down and if a slightly different curve is needed routed out. There are plenty of pre formed track ways to allow the boards to be cut down and not have to route out new channels. The feeds to the different rooms are laid in insulated formers without the radiant foil on top. The reason is you don’t want to add heat to a passageway or other room the feed pipes go through before getting to the designated room they heat.

After a lot of head scratching, where initially the plan was to lay tiles directly on top of it in the bathrooms and to add the defined boards over the top of it for carpeted areas, I decided to screed it! This will be bagged screed, flexible and compatible with the system. It can be very thin compared to pumped screed, so ideal for maintaining head room through doorways as well as ensuring the best heat transfer into each room. The floor in the older part of the house isn’t precisely flat and level, and the screed will ensure that the tiled bathrooms have a nice finish of the tiles to the floor, ie not cut / cut ti accommodate a slant. There won’t be much difference in price between the boards and screed.

OK, the latest update. Every day is a school day! And we learnt the wrong way that not fully reading the manufacturers instructions can be very painful. So, the contractor bought for the upstairs the screed that will go over the pipes encased in the insulated boards. The front of the packet stated, suitable for UFH. Down it all goes, looks lovely…..until the next day


Its Bubbled!
What’s the reason for this slight hiccup? Well, although the screed says it’s compatible with UFH, when you get out the data sheet yoi find that it’s OK for under UFH but nit to be used to encapsulate the piping for UFH and defiantly not for use on spongy surfaces that are expanded polystyrene! So…….why do a job once when you can do it twice! So, every bit of what was laid has had to be lifted and removed, fortunately the screed came away from the backing board that carries the pipe, but all the pipe has had to be removed…..a couple of Kilometres. We now have the right screed! So, if you’re going down this path, check with technical of the proposed screed manufacturers. We are using Everbuild / Silkins screed, their technical is superb.
Where we had routed out the concrete to lay the pipe within the floor we had another learning curve, between laying the pipe and before it’s been screeded somebody damaged a bit of it. Clearly this was Mr Nobody. So after consulting with the tube manufacturer, who advised lift it, another 200 meters hit the skip. The tube has a deigned life of 200 years I discovered rather than the 100 I thought it had!
The other UFH has proceeded without a hitch….so far. a losses and and cement dry mix has been applied over the pipes fitted between the suspended floor. The pipes were placed on top of a DPM layer. Over the top the final floor boarding is laid.



It’s been a while since I last updated. It’s been a complete nightmare and still is not finished. The issues have been around the screed. We have put down and taken it up about 3 times. The first time the screed recommended by the supplier, which in previous posts I indicated had an issue, we found out was actually not suitable for UFH. So everything was ripped out and started again. The second attempt the screed supplied had sent a mix of bags of screed in date and out of date. The out of date stuff reacted and this had all to come up again. We are now just finishing attempt 3. We have used literally tonnes of screed and miles of piping that is now in the skip. To say I’m well and truly fed up of UFH is an understatement!!

This is one of the floors with reacted out of date screed in it.


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