Underfloor Heating With Screed Upstairs

Hi. Two years ago I put in undefloor heating and a Geothermal heat pump. Upstairs I was advised to put ply on my 9x2 joists. Then put battons on the ply spaced about 1 foot apart. between the Battens I placed 1" foil back insulation and then on top of that the underfloor pipe. Floor boards were then nailed onto the battens. The system works fine except I am getting a lot of noise and creaking from the floor boards. I am giving serious consideration to taking up the floor boards and putting a screed on top of the insulation and pipes, leaving the battens in place to use to level the screed. I would then glue the boards back in place. I do have a few concerns...

1 - Will the 9x2 joists be capable of withstanding the weight of the 3/4" of screed I'll be laying on top of it? I expect it would but just checking.
2- I was hoping to do one room at a time and mix the screed myself to minimise cost and messing up the house too much. Any advise on the screed mix?
3- How long should I leave the screed before putting the boards back down.
4- Any other flaws in what I am proposing.

Thanks a lot for your help.

Neilc78 said:

Hi. Two years ago I put in undefloor heating and a Geothermal heat pump. Upstairs I was advised to put ply on my 9x2 joists. Then put battons on the ply spaced about 1 foot apart. between the Battens I placed 1" foil back insulation and then on top of that the underfloor pipe. Floor boards were then nailed onto the battens. The system works fine except I am getting a lot of noise and creaking from the floor boards. I am giving serious consideration to taking up the floor boards and putting a screed on top of the insulation and pipes, leaving the battens in place to use to level the screed. I would then glue the boards back in place. I do have a few concerns...

1 - Will the 9x2 joists be capable of withstanding the weight of the 3/4" of screed I'll be laying on top of it? I expect it would but just checking.
2- I was hoping to do one room at a time and mix the screed myself to minimise cost and messing up the house too much. Any advise on the screed mix?
3- How long should I leave the screed before putting the boards back down.
4- Any other flaws in what I am proposing.

Thanks a lot for your help.

Click to expand...

1. impossible to tell without site investigation, and anyway, you would need a structural engineer to sign off.

It sounds like whats happening is the floorboards were laid incorrectly, they are scraping off the nails. If the UFH is working fine i wouldnt mess with it. Perhaps simply consider lifting floordboards, screwing OSB over battens and glueing floorboards back down.....

I looked at doing this just to get rid of my creaking/noise. In the end I took up the OSB which was nailed. Added more bridgers to the joists. Cut 3/4 PLY in to widths of 8" and screwed in to the side of the 9X2 joist to prevent them flexing. Put in insulation between each joist. Put down sheeps wool joist strip along each joist to prevent timbere to timber contact between the relaid OSB. This was screwed in. In one particular room there was a slight height difference so a second layer of OSB was screwed with a 3mm underlay between the two osb joists.. THere is now carpet in this room. Situation is its not 100% and it should be from what I have done. I have narrowed it down to origional bridgers that were nailed in. Nothing I could do with these as it would have affected my ceiling below. The only room that made a difference to was a room I put down 22mm engineered board (190mm width). THis room is pretty good. Even when the OSB was completly removed from the room and I walked across the bare joists creaking occured.

If I were you I would add the mix as my theory is that if you have a weight greater (concrete mix) than an average person then it should eliminate the problems. I would still screw in the PLY though. I was in a house a few years ago and they had this put in ontop of 9X2's. You would probably need to run it by an engineer though!

Thanks for the reply. I was hoping to avoid adding anything above the existing battens (Such as OSB) as that would mean a floor increase in height which means cutting doors etc which would be a big job.

Neilc78 said:

Thanks for the reply. I was hoping to avoid adding anything above the existing battens (Such as OSB) as that would mean a floor increase in height which means cutting doors etc which would be a big job.

Click to expand...

laying a screed will cause the same issue...

sydthebeat said:

laying a screed will cause the same issue...

Click to expand...

No it won't. Let me try and explain the layout I have again. 9x2" Joists. On top of the Joists is 3/4" (I think) Ply. On top of the ply are 1 3/4" high battens spaced at 1 foot intervals. Between the battens, and sitting on the ply, is 1" thick foil back insulation. The underfloor pipes sit on top of the insulation and these come up level with the battens.

I am proposing putting screed on top of the insulation and bringing it up to the height of the battens (no higher, so about 3/4" of screed). When dry I will then glue down the battens onto the screed. So I will have no net height gain on the floor.

Have a look at this link, model 1, for a schematic of my system.

[broken link removed]