Insulating pipes under timber floors

[TerryWaite]

looking for some opinions on whether or not people generally insulate hot/cold/heating pipework under suspended timber floors? I mean typically upstairs in a house with a heated room underneath. Obviously you would insulate in a loft/ garage. My reason for asking is if you are only allowed to notch 0.125 x the depth of a joist, how can you possibly run a 22mm pipe, which has to sit in a clip, with insulation round the pipe too, that adds up to about 40mm.

Also, what do you do when you have to run a waste pipe from a shower tray across the joists to outside? how can you notch joists for a waste pipe? Assuming customer doesnt want the tray on a raised base as well they want it on the floor. id appreciate any opinions on this. cheers.

 

[ADM360]

I the pipe work in internal then not usualy, only if it a secondary return, as its an interanal space risk of freezeing is very small, although pipes under a suspended timber ground floor I wood insulate as these are vented and suseptable to frost! as for notching, it all depends on the joist! most floor joist can be notched deep enough to accept a 22mm pipe some even a 28mm, all depends on the depth of joist. if you use platic pipe you can drill though the center of the joist which allow a great hole for pipes. but I have yet to find a joist that has the depth to allow you to put a waste pie though it!! as when you drill it has to be ing the middle of the joist. if you can't run the waste parallel to the joists then it will have to go on top or below!


hope this is of some help!!

 

[TerryWaite]

Thanks, you have answered it all in one post! well, nearly just what i was looking for. So you wouldnt generally insulate under a bathroom floor on 2nd floor of a house, just ventilated and draughty spaces? Would it not make the hot water/heating less efficient? As you are heating a floor space? say if you have 30 metres of pipe supplying the radiators and bathrooms on the top floor? or is it minimal? cheers

 

[SimonJohns]

More insulation the better. I would lag it in my own house. Just for energy efficiency. Not for frost protection

 

[ADM360]

I would look at that as mimimal, you could lag everything but as the pipes are in a heated space (so to speak) this could be classed as unnessary expense, but then again most floor voids are now being insulated to cover new building regs (I think). I would insulate where heat loos was a problem or heat transfer could occur. ie secondary hot returns, heating and cold pipe work in the same voids.


Hope this is of some help!!

 

[tamz]

You don't check pipes into joists of suspended wooden floors, you sling them underneath insulated with 19mm (22mm) and 25mm (15mm) insulation clipped up with galvband.

 

[TerryWaite]

how do you sling them underneath if the plasterboard ceiling is fixed to the underneath of the joist? and whats galvband? cheers.

 

[tamz]

There is no gyproc below a ground floor.
Galvband - galvanised all round band
Mark Vitow Ltd - Plumbing & Heating/Fixings/Other Fixings/All Round Band Galv 12mm x 10m

 

[stevetheplumber]

mostly we use felt lagging below ground floors and nothing on upper floors
as tamz says you dont notch joists in ground floors its amazing what you can get in through a 2 board hatch
did come unstuck on a job once when we priced we could see it was a wood floor when we started we found it was wood floor laid on three quarter batten on a concrete slab ooops

 

[TerryWaite]

thanks I was on about a first floor though with plasterboard attached to joists u/neath

 

[tamz]

thanks I was on about a first floor though with plasterboard attached to joists u/neath

No choice other than to notch or drill. Generally upstairs joists are 9" or 10" deep but sometimes less. You can check these out no problem to take 28mm pipe. Easiest and quickest way to get them all the same is with a circular saw set to depth.
8" and below joists would not be able to take a check deep enough for 22mm pipes. As if that doesn't happen every day!

did come unstuck on a job once when we priced we could see it was a wood floor when we started we found it was wood floor laid on three quarter batten on a concrete slab ooops

You need to look for the vents Steve :wink:

 

[Best]

Not a lot you can do with pipes notched into joist unless you keep them slightly deeper & use the thinner 9mm insulation. You don't need clips on pipes in joist that mean you cutting track deeper. Depends where joist are going to be cut or drilled as to what's best. Tracks should only be near to where a joist is supported & not in the middle of joist. If you really really had to drill a joist ( with right angled drill) for a waste pipe, if it was a short span joist which is a also fairly deep, then it can be fine.

 

[AWheating]

On new build you lag every inch of hot and cold pipework but most dont adhere to this in exsisting housing but i think its a requirement of part L to do so.

as for drilling and notching for waste pipes (or any pipes) just follow the regs and you cant go wrong.