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How to fit acoustic insulation to Posi joists


Hilldes

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8 hours ago, saveasteading said:

.... or if there was an actual gap between end-to-end joists or joist to wall that would allow a turn. ONLY with permission of the joist designer.

There are some opportunities to reduce threading through joists e.g. this one where the top chord of the posi is supported on the glulam beam and the bottom chord is cut short. 

IMG_1397.jpg.b16500b045c17a6d412febf8d7614389.jpg

Unfortunately, most of the joist ends are not like this.

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I don't fancy doing that from underneath.

Revert to plan B or C. Secondary floor if headroom allows, or extra large and efficient radiators to compensate for the lower temperature water.

 

Think of low temp rads as a good thing....in schools it is necessary to build guards over hot radiators to protect against burning of little people.

 

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@Hilldes how did you get on attempting from below?

It's certainly possible, I managed it with a little help.

Trick seemed to be get the loops formed at the beginning and then enlarge each loop in turn.

My joists are 400mm centres and I put a loop in alternate gaps.

 

 

IMG_20210118_092551.jpg

IMG_20210118_131637.jpg

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Thanks for the tips and pics @willbish. We had a play that involves a similar technique - thread the pipe straight through the line of joists in a straight line then withdraw a loop down a gap between two joists. See pic. This worked really well - the pipe was on the decoiler outside in the sun on a hot day. Will try for real in a few days (need to complete fire protection lining of the plant rooms - a separate thread). Plan will be to withdraw one loop then secure in spreader plates from below before pulling down the next loop. Then cut pipe from the decoiler and thread through for the return back to the manifold. Hoping the warm weather will return.

A4468E91-3837-430B-ACE8-B7EF8EAC4EE7.jpeg

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41 minutes ago, Hilldes said:

thread the pipe straight through the line of joists in a straight line then withdraw a loop down a gap between two joists

I tried this initially and ended up with kinked pipe. If you create a loop in each section whilst feeding through the joists you won't have such tight bends. See how my pipe crosses itself.

 

Go with this technique and it's a doddle ??

IMG_20210725_221537.jpg

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27 minutes ago, willbish said:

I tried this initially and ended up with kinked pipe. If you create a loop in each section whilst feeding through the joists you won't have such tight bends. See how my pipe crosses itself.

 

Thanks @willbish will try your technique.

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On 22/07/2021 at 18:19, Faz said:

If your BCO sees 'notched' joists you are going to be in a world of trouble - best not go down that route.  I have the spare ways on the manifold and, looking at all the issues, quickly decided that mats were the way to go.

Agent electric matts expensive to run, even the low wattage ones?

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  • 4 weeks later...

A quick update on threading pert-al-pert pipe through posi joists and fixing with spreader plates. Now completed the first section for real with loops pulled down between joists and not a single kink. Takes some time to plane the route to pull through and time consuming to complete the install. I did price up switching to Wunda over floor, but that added £5K and I suspect would not be much quicker in areas that require duo boards to be laid on to of Wundatherm.

 

 

9651A532-B46F-49FF-82A1-1B83DA3028AE.jpeg

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  • 1 month later...
17 hours ago, Hastings said:

Isn't there a section of 2x4 strongback missing in the last photo?

 

All the joists should be cross-connected to each other I think?

Thanks for pointing it out @Hastings. I’ll have a look at other areas of the house to compare.  All joists have noggins where they meet internal and external walls, but I’m not sure about the timber you refer to mid-joist. The joists were delivered as cassettes which May explain it.

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On 16/07/2021 at 08:44, nod said:

Use 600 wide rolls and push it between the 400 centres Sitting on the bottom edge 

 

I must be being stupid, but could you confirm that you really mean use 600 wide stuff for 400 joist centres? Only, the gap between the posi joists chords is only 300. Never used it before but it seems like squeezing 600 stuff into a 300 gap would be hard and would also reduce the effect of it due to too much compression?

 

I am about to insulate mine and I had planned to use 100mm thick acoustic roll and use the ready cut 400 widths to push up there (and not bother getting inside the joist voids too much). Is that a bad way to go?

 

Thanks.

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