Joshua Graham

Mike, thanks for the reply. Yes i have already done a bit of air tightening of the floor using a dpm between the floor board and joist which was taped to the plaster forming a somewhat decent air barrier. I also have 100mm PIR board between joists. Should mention another reason i would do it is to make maintenance easier and cleaner as i may need to under there a few more times and possibly again in the future also. For that alone it is worth it to me, I would also like to know if covering the area with a dpm would cause issues. It is only one room and a small room 1.8x 1.9 bathroom.

Hello, I have been doing plumbing under my floor which has required me to crawl in the under floor a lot. In there, there is some old bitumen on top of the sand. I believe its there to stop moisture coming in through the ground. Problem is, it is all broken up as black jack gets fragile over time so is no longer serving its purpose. The ground is cool damp to the touch even after being left for a couple years. There are definitely no leaks causing it, it is likely there from a previous leak that has been addressed. I wanted to know if it is worth running a DPM over the top as i have a good bit spare of heavy gauge DPM. I was thinking running some weed fabric to protect it from punctures as there is rubble dotted about and maybe the odd screw, then run the DPM on top of it and finally adhere the DPM to the walls below the DPC by a few bricks using expanding foam. Would this be worth it? Would it help keep it dry under there and would it be OK to do so? Any advice is greatly appreciated, thank you. See my diagram below if needed.

Thanks for the answer.

Can I use ptfe anf the paste together? Also thank you for the reply.

So the female section is a shower controls and like the male section is brass construction. I have applied 5 revolution of clockwise PTFE tape. Tried tightening it more, but still it leaks.. Why? What have I got wrong? I will upload pictures tomorrow as the pictures i took today do not work. Anyway thanks in advance to any plumbers who help.

Yes, we did do it about a year ago, which is where the 100mm pipe center came from. But much has changed since then, the property is not airtight, but it is certainly tighter than most and all insulative measures have been carried out. It may be worth another calculation. Do you see any issues with the structure proposed in the diagram (beyond insulation), would this all be functional from a structural perspective?

I should have mentioned, there is also mineral wool below the pir, to the remaining depth of the joist. In terms of high flow rates, that is the whole purpose of using 100mm centers, the pipes should run at a lower temp should they not? what would your recommendation be?

Hi, As is attached, the image shows a crosssection of the layers in the underfloor heating system I am planning. I have got a company that is giving me a good deal on routing ply for use as an low profile under floor heating system. The system brings the floor up by 30mm; 6mm cement fiber board, 18mm structural ply and 6mm xps insulation. it will be in a living room and kitchen area and is a wet system. I want to know, If anyone sees any immediate issues with it as shown in the diagram, my doubt I have is if the xps will be rigid enough to support such a system but the reason I was thinking this, is to bring it up to 30mm as it brings the floor exactly level with the rest of the house and a little more insulation never hurt, though it is sandwiching the subfloor because a vapor control layer, so maybe it would hurt if water got in... Please let me know if you would do a system like this any differently, I already have the ply, pipes, spreader plates as surplus from a pervious job, so I am planning to work them in no matter what.

Basically, i actually lowered the ground. at the brick (its about 300mm above ground), but behind the brick is a joist which blocks airflow a bit, cutting holes in the joist is not an option. Periscopic vents are possible but would be a massive hassle and mean removing a small amount of brick work. so my idea was to remove the brick (cover the hole with fine mesh) to allow more air in. Just want better movement of air.

Hi, I was wondering if it is possible to increas ventilation in my underfloor by removing the airbricks as they got clogged with debris over time. I'd basically have a hole with some mesh and a small cowl to protect it from rain splashing in. More air would get in, but would it damage the structure to remove an airbrick without replacing?

Thanks for that!

Hi John, Yes the radiators are set to run at 35 degrees, basically oversized. I used a couple calculators to work out the btu sizes for the temp. Its also regulated by digital thermostats. I want to avoid using TRVs on my radiators as I prefer the digital thermostats on the walls with a couple extra thermometers around the rooms. A very similar pump, brand and model etc, has a 6.5m delivery head, which from what I have read, represents the max it can push water against gravity. The radiators are about 3.5m max above the pump, would it stand a chance? What else should I consider?

Hi, I am setting up an underfloor heating circuit with a control unit, thermostats and actuators. On the last 3 ports of the manifold will be rads, 2 are upstairs. Would something like this usually be a problem for ufh pumps? Would I need a bigger pump than the standard types?

Engineered wood. so less movement allowed than carpet but a touch more than tiles i guess tho. With the egg crates would i need to put a vapour barrier under? I already have one under the existing chipboard see to stop cold air traveling up gaps. I think this could cause a breathability issue.

I do like the idea of screed as is it retains gets a slower more even release of heat my only worry is if it cracks due to floor movement... the joists have a bit of movement on them, would that be an issue?

I can build up if need be, yes, what is the suggestion?

Thanks for the help, that spreadsheet will come in super handy! Ye the CNC part I was meaning lay 22mm ply atop the existing new 22mm chipboard, this way I can make custom shapes for the loops. The reason I opted out of screed is my floor is suspended and the joists might not take the extra weight or could sag in places, and move which would crack the screed. What are your thoughts?

I should have said the floor type is engineered oak, 10mm depth, the system uses a valiant unitower to.

Hi, I am currently renovating a 60s property as my first home. I am getting an air source heat pump installed, as oil is no longer a financially viable option. I want to run my heat pump at 35 to heat the house using underfloor heating on the ground floor. The ground floor is suspended timber floor, with new sheets of chipboard down. I have been looking into systems that you can lay atop the existing floor and was looking for advice as to what type of pipe centers for this as some places have said 100mm but there are no products out there that do pipe centers this close! I think its worth noting I have underfloor insulation of 60mm of pir and 150mm of mineral wool, and a membrane to protect against drafts, 600mm mineral wool in eves and bead cavity filling. I have also filled any openings i could find, to prevent air leaks. Are 100mm center overkill? Would 35 degrees work at 150mm centers or even 200mm? If not, could I cnc the center my self into my existing chipboard floor or a layer on top of the existing chipboard then lay 6mm of ply? Thanks JG

Hi, new member here, but have been reading this forum for a while. Currently renovating a 60s property as my first home. I am getting an air source heat pump installed, as oil is no longer a financially viable option. I want to run my heat pump at 35 to heat the house using underfloor heating on the ground floor. The ground floor is suspended timber floor, with new sheets of chipboard down. I have been looking into systems that you can lay atop the existing floor and was looking for advice as to what type of pipe centers for this as some places have said 100mm but there are no products out there that do pipe centers this close! I think its worth noting I have underfloor insulation of 60mm of pir and 150mm of mineral wool, and a membrane to protect against drafts, 600mm mineral wool in eves and bead cavity filling. I have also filled any openings i could find, to prevent air leaks. Are 100mm center overkill? If not, could I cnc the center my self into my existing chipboard floor or a layer on top of the existing chipboard then lay 6mm of ply? Thanks JG