As part of the kitchen refurbishment I am looking to insulate the floor whi
ch at present is a suspended T&G floor on 100mm joists. I am looking at fix
ing 25 X 25 battens to the bottom of the joists and dropping 75mm foam insu
lation in between the joists. Any advice regards preferences between Kingsp
an or Celutex or is it just a case of whichever I can get at the best price
it is just a case of whichever you can get at the best price.
No need for the battens either - just wedge the sheets in place and use
expanding foam to fix and fill any gaps. Remember to foil tape over the
joists as well..
Socialism is the philosophy of failure, the creed of ignorance and the
gospel of envy.
The insulation is very light and when cut to be an interference fit
all the battens are for doing is acting as a stop. 20 x 6 lath will
do that and be easier to fix. I'm assuming that the crawl space under
the joists is not big enough to squeeze through to shove errant
sections of insulation back up.
Provided the boards are a tight fit with no big gaps they don't need
to be foamed in, tapping will be fine. However as they are 25 mm
below the top of the joists taping the internal 90 degree joint might
be a challenge.
But with the joints taped there can be no "leakage up the sides of
the joists". I did think about the gap betwixt insulation and
flooring and sort of decided that a bit of warm side ventilation
wouldn't be a problem.
25x25 batten at the bottom and sides of the joists wouldn't be too
tricky to fit. I'd use a jig to set the postion though not rely on
the joists and/or insulation actually being the dimensions they
proport to be.
Well yes it *is*, actually. If there is any exposed joist, that is
*precisely* where condensation will happen. The foil doesn't just seal,
it is impermeable as well. You MUST ensure that the no-longer-ventilated
cold joists are taped over. It so happens that is simpler if the
insulation is flush with the joist tops.
Underfloor ventilation in an insulated scenario has no purpose: You wont
get condensation where its warm.
Make up battens with slotted holes so you can get the batten the depth
of the insulation below the joist top, then screw in more screws to
Insulate, foam in any air gaps, and tape over.
"Women actually are capable of being far more than the feminists will
You may be able to achieve perfection but it is rarely within my grasp
:( Especially perfection that has to survive thermal cycling and
movement over the years.
But I can't swear that flush fitting is not just a myth that
manufacturers et al have bought into.
reply-to address is (intended to be) valid
On Sat, 1 Aug 2020 09:19:40 +0100, Tim Lamb wrote:
Power tool to cut celotex type rigid foam board? Seems a bit OTT.
A hand saw will do it but generate a lot of bits that'll be great fun
with any static electricity (but probably not as fun as the bits from
expanded polystyrene). Deep score with a stanley knife 'n snap works
for 25 mm not tried that on thicker boards. For thicker borads I'd
try a scallop bladed knife, possibly with some thin wedges to keep
the cut open.
I read that score'n'snap may not give a straight edge on thicker boards. So
you would likely have gaps where the insulation is thinner, and harder to
butt pieces together or have a tight fit against joists.
You can get special insulation hand saws:
(Amazon.com product link shortened)
For power tools there's this sort of thing, but it ain't cheap:
If you have a big job to do, I wonder if they might be hired?
Which will shower you with PIR dust !!!.
Bosch make a special 4 inch cutting blade with a smooth knife
edge that fits any compatible jig saw.
Or sharpen the back of a hacksaw blade into a knife, stick a handle
on one end and cut them carefully.
Lay some fine guage chicken netting over the joints and loop
down so that the PIR board is held tighly up against the flooring.
On Friday, 31 July 2020 08:20:34 UTC+1, Tricky Dicky wrote:
hich at present is a suspended T&G floor on 100mm joists. I am looking at f
ixing 25 X 25 battens to the bottom of the joists and dropping 75mm foam in
sulation in between the joists. Any advice regards preferences between King
span or Celutex or is it just a case of whichever I can get at the best pri
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