richo106 Posted January 30, 2022 Share Posted January 30, 2022 Hi all We are planning to install UFH throughout our property. We will be installing posi joists to aid with ducting for MVHR We are planning to use aluminium spreader plates, then 22mm T &G flooring, my question is how to get away with not notching the joists for the loops? Is Wunda the best place for a self builder to get plans and materials from for UFH? Many Thanks Link to comment Share on other sites More sharing options...
JohnMo Posted January 30, 2022 Share Posted January 30, 2022 I used Outsourced Energy for my materials. Did my own plans, using a free trial of loopcad. As you are not allowed to notch Posi joists, would you take bends through the gaps in the joists? That seems to be the only option. Link to comment Share on other sites More sharing options...
ProDave Posted January 30, 2022 Share Posted January 30, 2022 Your 2 choices are feed the pipes through the web of the joists, but on anything other than a very small room that is going to be a very tedious process feeding a long length of pipe through every web. Or lay battens on top of every joist and you can of course notch or leave gaps in the battens, but that will raise your floor height by 25mm or so so you have to design everything else, e.g. door openings and ceiling heights to allow for that extra build up. Link to comment Share on other sites More sharing options...
markc Posted January 30, 2022 Share Posted January 30, 2022 Is this ground or upper floor? Where will the insulation be? Link to comment Share on other sites More sharing options...
richo106 Posted January 30, 2022 Author Share Posted January 30, 2022 41 minutes ago, markc said: Is this ground or upper floor? Where will the insulation be? Upper floor, ground floor is new concrete slab with 200mm PIR Link to comment Share on other sites More sharing options...
nod Posted January 30, 2022 Share Posted January 30, 2022 I would really look at your insulation spec if you feel that you will need UFH in the bedrooms We have 158 of UFH throughout the GF Radiators in all five bedrooms and galleries landing We’ve never used the radiators in the bedrooms in three years we have been here Link to comment Share on other sites More sharing options...
richo106 Posted February 1, 2022 Author Share Posted February 1, 2022 I have just spoken to Wunda about UFH on my first floor I was planning on using spreader plates under the T & G flooring and install acoustic insulation below However they have just replied saying that spreader plates are not suitable to use with ASHP and can only be used with boilers Has any body else come across this? Is there any other methods they could recommend? Many Thanks Link to comment Share on other sites More sharing options...
LA3222 Posted February 1, 2022 Share Posted February 1, 2022 (edited) Not sure why people advocate not bothering with heating upstairs - smacks off a my house is mega, it doesnt need it. Not sure why you would bother other than bragging rights. If you can supply heat over Double the footprint then you are halving the amount of work required per m2 and make it easier to heat up the house consistently. I put my pipes down on the first floor over the deck in a pug mix. Then put a new floor deck over the top. Another reason I wanted it upstairs is that I heat the bathrooms using floor probes so the tiles are always warm to stand on. No getting out of a shower and feeling like you are stood on cold tiles. Edited February 1, 2022 by LA3222 Link to comment Share on other sites More sharing options...
ProDave Posted February 1, 2022 Share Posted February 1, 2022 UFH works fine with an ASHP and spreader plates. Just do it. Ignore the ignorant sales person. Link to comment Share on other sites More sharing options...
Dudda Posted February 1, 2022 Share Posted February 1, 2022 If you're filthy rich and want a really solid warm floor you can get posi joists specified to take the weight of a 50mm self leveling liquid screed with UFH pipes in it. I did this for a client recently. If feels like hollowcore its so solid and the soundproofing is so good. Aluminium spreader plates are fine though with a 25mm batten as suggested above. Link to comment Share on other sites More sharing options...
Happy Valley Posted February 1, 2022 Share Posted February 1, 2022 We have just been fitting our between posi joists insulation this week which has the cut outs for the 16mm UFH pipework. We have decided to router out 16mm across the top of each joist to get the pipe to the next area so we don't have lots of ups and downs. We will then be laying floorboards and an engineered wood floor. Ground floor is same as yours - concrete slab and 200mm insulation. We used Wunda as well - a great firm who have sent out more materials to us today without a further charge. Link to comment Share on other sites More sharing options...
ProDave Posted February 1, 2022 Share Posted February 1, 2022 3 minutes ago, Happy Valley said: . We have decided to router out 16mm across the top of each joist to get the pipe to the next area so we don't have lots of ups and downs I have never seen that as an approved method. Link to comment Share on other sites More sharing options...
jack Posted February 1, 2022 Share Posted February 1, 2022 32 minutes ago, Happy Valley said: We have decided to router out 16mm across the top of each joist to get the pipe to the next area so we don't have lots of ups and downs. I recently looked into drilling a small hole in an existing posi joist and all the evidence suggests no form of drilling or notching is allowed. Have you checked this? Link to comment Share on other sites More sharing options...
ToughButterCup Posted February 1, 2022 Share Posted February 1, 2022 49 minutes ago, Happy Valley said: ... We have decided to router out 16mm across the top of each joist .... In our case 16mm would be just under half the chord of some of our POSIs. And thats a lot. I'm not an SE, but out of caution may I suggest you consider sistering or perhaps some other form of stiffening or support where you have cut part way through the POSI ? Link to comment Share on other sites More sharing options...
SteamyTea Posted February 1, 2022 Share Posted February 1, 2022 26 minutes ago, jack said: 59 minutes ago, Happy Valley said: We have decided to router out 16mm across the top of each joist to get the pipe to the next area so we don't have lots of ups and downs. I recently looked into drilling a small hole in an existing posi joist and all the evidence suggests no form of drilling or notching is allowed. Have you checked this How do they cope with screwing down floorboards? Link to comment Share on other sites More sharing options...
Happy Valley Posted February 1, 2022 Share Posted February 1, 2022 1 hour ago, jack said: I recently looked into drilling a small hole in an existing posi joist and all the evidence suggests no form of drilling or notching is allowed. Have you checked this? Awaiting a response from the manufacturers - ours have 47mm of wood depth before the void the another 47mm. Link to comment Share on other sites More sharing options...
jack Posted February 1, 2022 Share Posted February 1, 2022 1 hour ago, SteamyTea said: How do they cope with screwing down floorboards? According to the posi joist technical handbook, holes and notches are forbidden, but fixing flooring and strongbacks etc is allowed: Link to comment Share on other sites More sharing options...
dpmiller Posted February 1, 2022 Share Posted February 1, 2022 we did poured screed over caberdek on posijoists and it's didn't add a lot of hassle, didn't make the joists massive either. Link to comment Share on other sites More sharing options...
jack Posted February 1, 2022 Share Posted February 1, 2022 8 minutes ago, dpmiller said: we did poured screed over caberdek on posijoists and it's didn't add a lot of hassle, didn't make the joists massive either. MBC offered to engineer our joists to take a 50mm poured screed and I'm sure it wasn't that much more cost-wise. The real cost would have been getting the screed done. Link to comment Share on other sites More sharing options...
Gus Potter Posted February 1, 2022 Share Posted February 1, 2022 5 hours ago, Happy Valley said: We have just been fitting our between posi joists insulation this week which has the cut outs for the 16mm UFH pipework. We have decided to router out 16mm across the top of each joist to get the pipe to the next area so we don't have lots of ups and downs. We will then be laying floorboards and an engineered wood floor. Ground floor is same as yours - concrete slab and 200mm insulation. We used Wunda as well - a great firm who have sent out more materials to us today without a further charge. Don't touch the flanges of the posi joists.. it's dangerous, a big safety risk and you could really trash your house.. 2 Link to comment Share on other sites More sharing options...
saveasteading Posted February 2, 2022 Share Posted February 2, 2022 5 hours ago, Happy Valley said: We have decided to router out 16mm across the top of each joist NOOOOOOOOOOOOh. I am repeating the wise (and crucial) advice from above. If you don't understand the reason, I suggest looking into it as it is a fundamental part of building knowledge. (Unfortunately, many plumbers and electricians don't know this either (or perhaps don't care), and damage the buildings they work on). Link to comment Share on other sites More sharing options...
Carrerahill Posted February 2, 2022 Share Posted February 2, 2022 5 hours ago, Happy Valley said: We have decided to router out 16mm across the top of each joist to get the pipe to the next area so we don't have lots of ups and downs. STOP! Link to comment Share on other sites More sharing options...
richo106 Posted February 2, 2022 Author Share Posted February 2, 2022 14 hours ago, ProDave said: UFH works fine with an ASHP and spreader plates. Just do it. Ignore the ignorant sales person. This was the reply from Wunda: ‘it is due to the pipe centres and heat outputs with spreader plates. And guarantee will be nil and void if it does not work correctly’ But if people on the forum have used this method before I am happy to go with their opinions Link to comment Share on other sites More sharing options...
Andehh Posted February 2, 2022 Share Posted February 2, 2022 As above in notching, though electricians & plumbers willfully carry it out in a very regularly basis. Sister the joists if you have already done it, & suggest screwing a metal plate over the pipe to avoid screws being driven into the joust overlap. Providing you arnt loading the floor up excessively you should be fine... Its just bad practise. Link to comment Share on other sites More sharing options...
SteamyTea Posted February 2, 2022 Share Posted February 2, 2022 (edited) 1 hour ago, richo106 said: ‘it is due to the pipe centres and heat outputs with spreader plates. And guarantee will be nil and void if it does not work correctly’ As long as your calculations show that there is enough power delivered at the lower temperature, I can't see a problem. Edited February 2, 2022 by SteamyTea Link to comment Share on other sites More sharing options...
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