Fixing PUR board insulation to timber joists

[pachmarhi]

I want to insulate the ground floor of the house. It is a suspended timber floor and the boards are all up anyway, for other reasons. The joists, however, are only 100 deep. What I want to do is to fix 75mm of PUR insulation to the bottom of the joists (to increase depth of insulation and to reduce thermal bridging along the joists) and then fill the space between with glass wool insulation. I know it is going to be a bit fiddly to get the insulation under the joists, but it will be possible, though I will have to cut the boards. What fixings should I use to secure the board insulation under the joists?

 

[Shytalkz]

Nail a batten on the side of the joist at the correct depth of the insulation down from the top of the joist and sit the insulation on that.

 

[pachmarhi]

I'm not trying to place the insulation BETWEEN the joists. I want to place it UNDER the joists.

 

[Shytalkz]

Alright, so I skim-read the post, no need to take umbrage . How much room have you got under the joists?

 

[^woody^]

<note to self>

Check all Shys beam calculations in future to make sure he has not speed read the equations and put the beam in-between the floor and not underneath it to hold it up lol

The OP needs to get the retainer clips as used for cavity walls. This usually slips on a wall tie, but in this case they can be nailed to the joist through the insuation and the clip holds it up

 

[pachmarhi]

Hey, no umbrage taken! I was just trying to emphasise the important bits.

I have 380mm below the joists. I've now spoken to Kingspan. They say I need a fixing with head/washer at least 35mm. One of the things they recommended was this http://www.ejot.co.uk/build_htk-tkr.htm but had difficulty locating supplies.

 

[pachmarhi]

The OP needs to get the retainer clips as used for cavity walls. This usually slips on a wall tie, but in this case they can be nailed to the joist through the insuation and the clip holds it up

Just seen your post. Thanks. Will look into that.

 

[Shytalkz]

note to self

Check all Shys beam calculations in future to make sure he has not speed read the equations and put the beam in-between the floor and not underneath it to hold it up lol

Very good. Git.

 

[Shytalkz]

The OP needs to get the retainer clips as used for cavity walls. This usually slips on a wall tie, but in this case they can be nailed to the joist through the insuation and the clip holds it up

I wouldn't have thought of that..extremely logical though. Damn....