insulating then boarding an attic - is it worth increasing joist depth first?
 

Looking to board my attic for storage; it has some scrappy Rockwool
and joists are 4"x2". I was wondering whether to plant 2"x2" timbers
on joists to allow for greater depth of Rockwool, or maybe the
chipboard would provide enough extra insulation? Another thought -
better grade insulation material in place of Rockwool but in the same
4" space? Any ideas welcomed.

insulating then boarding an attic - is it worth increasing joist depth first?
 

wrote:
Looking to board my attic for storage; it has some scrappy Rockwool
and joists are 4"x2". I was wondering whether to plant 2"x2" timbers
on joists to allow for greater depth of Rockwool, or maybe the
chipboard would provide enough extra insulation? Another thought -
better grade insulation material in place of Rockwool but in the same
4" space? Any ideas welcomed.

If you add 2x2 timbers on top of the existing joists you are still 4 inches
short of the recommended 10 inches of loft insulation. Have you considered
also putting insulation between the rafters, say 4 inches?

insulating then boarding an attic - is it worth increasing joist depth first?
 

wrote in message
ups.com...
Looking to board my attic for storage; it has some scrappy Rockwool
and joists are 4"x2". I was wondering whether to plant 2"x2" timbers
on joists to allow for greater depth of Rockwool, or maybe the
chipboard would provide enough extra insulation? Another thought -
better grade insulation material in place of Rockwool but in the same
4" space? Any ideas welcomed.

Insulation value of chipboard is negligible. Best put high performing foam
insulation between the existing rafters. Install 4"x2" joists over the
existing at 90 degrees to the existing joists, have a 6" screw through to
secure the joists, and then put cheaper rockwool between these, then
chipboard over. Check if the existing ceiling can hold the weight.

Also seal all holes in the ceiling with silicon to prevent draughts, where
cable and pipes run through. Have a sealed and insulated loft hatch. Your
fuel bills will then drop.

insulating then boarding an attic - is it worth increasing joistdepth first?
 

wrote:

Looking to board my attic for storage; it has some scrappy Rockwool
and joists are 4"x2". I was wondering whether to plant 2"x2" timbers
on joists to allow for greater depth of Rockwool, or maybe the
chipboard would provide enough extra insulation? Another thought -
better grade insulation material in place of Rockwool but in the same
4" space? Any ideas welcomed.

If you are looking at better grade insulation, you could simply lay a
rigid foam board insulation over the joists and then screw the flooring
down through it. No need for extra battens etc, and no additional weight.


--
Cheers,

John.

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insulating then boarding an attic - is it worth increasing joist depth first?
 

On 16 Oct, 00:21, wrote:
Looking to board my attic for storage; it has some scrappy Rockwool
and joists are 4"x2". I was wondering whether to plant 2"x2" timbers
on joists to allow for greater depth of Rockwool, or maybe the
chipboard would provide enough extra insulation? Another thought -
better grade insulation material in place of Rockwool but in the same
4" space? Any ideas welcomed.

Dear Peter
You need to address the issue of the strength of the 100 mm joists and
their span wrt their storage capacity. If the storage is light and
next to the bearings (ie small objects or old boxes) then no problem
but there is not likely to be much use to the area with such
limitations. If you wish to store heavier stuff then you need to
provide mid span support or beef up the strenth somehow. Not to do
this will put you at risk of long term deflection of the joists due to
"duration of load" effects.
I concur with the others that your best route is to put in 3" of
Kingspan or the like leaving 25mm gap under the slates in between the
rafters and you can always add inside.

If this does not appeal on cost grounds and you wish to do the ceiling
joists regardless bear in mind the following
you need min 300mm rockwool or the like
you need to lay first layer with the joists and overlapping
next layer at 90 degrees
eaves ventilation facility
a vapour check under the insulation
To get storage on this you will need blocks on the joists close to
the bearings and run bigger joists on top - quite expensive and not a
good structural solution and even then limited to loading

to get a good loading you need a good well-engineered structure

Chris

insulating then boarding an attic - is it worth increasing joist depth first?
 

wrote in message
ups.com...
Looking to board my attic for storage; it has some scrappy Rockwool
and joists are 4"x2". I was wondering whether to plant 2"x2" timbers
on joists to allow for greater depth of Rockwool, or maybe the
chipboard would provide enough extra insulation? Another thought -
better grade insulation material in place of Rockwool but in the same
4" space? Any ideas welcomed.

I would use the new multi-layer reflective stuff stapled to the inside of
the rafters. Much easier to do than foam sheets, and your loft would not get
as hot/cold.

insulating then boarding an attic - is it worth increasing joist depth first?
 

On Oct 16, 12:21 am, wrote:
Looking to board my attic for storage; it has some scrappy Rockwool
and joists are 4"x2". I was wondering whether to plant 2"x2" timbers
on joists to allow for greater depth of Rockwool, or maybe the
chipboard would provide enough extra insulation? Another thought -
better grade insulation material in place of Rockwool but in the same
4" space? Any ideas welcomed.

Make sure you don't end up with condensation forming in the loft due
to the reduced temperature. The previous occupants in my house had
extra insulation with no vapour barrier and no ventilation.

MBQ

insulating then boarding an attic - is it worth increasing joist depth first?
 

"Brian" wrote in message
...

wrote in message
ups.com...
Looking to board my attic for storage; it has some scrappy Rockwool
and joists are 4"x2". I was wondering whether to plant 2"x2" timbers
on joists to allow for greater depth of Rockwool, or maybe the
chipboard would provide enough extra insulation? Another thought -
better grade insulation material in place of Rockwool but in the same
4" space? Any ideas welcomed.

I would use the new multi-layer reflective stuff stapled to the inside of
the rafters. Much easier to do than foam sheets, and your loft would not
get
as hot/cold.

It is a pity it is very expensive and doesn't work too well.

insulating then boarding an attic - is it worth increasing joist depth first?
 

On 16 Oct, 00:21, wrote:
Looking to board my attic for storage; it has some scrappy Rockwool
and joists are 4"x2". I was wondering whether to plant 2"x2" timbers
on joists to allow for greater depth of Rockwool, or maybe the
chipboard would provide enough extra insulation? Another thought -
better grade insulation material in place of Rockwool but in the same
4" space? Any ideas welcomed.

It sounds as if you are asking 2 things:
1) boarding the loft
2) insulating the ceiling against heat loss

The best way to insulate your ceiling is at ceiling joist level not at
rafter level, that is for loft conversions.
4x4 joists should be fine for general storage as long as they are at
400mm crs and not overspanned. Heavier loads should be kept over load
bearing walls or near the joist ends.
If you have plasterboard ceilings you will have virtually 100mm depth
available so drop in 90mm Celotex, Xtratherm Ecotherm or similar
ridgid boards cut as a good fit between the joists. To seal any slight
gaps run aluminium tape across the top of the joists overlapping onto
the boards, it's fairly cheap for a 100mm wide roll. The just lay
boards over. Don't use MDF as it is heavy, go for building ply, it's
light and strong and if screwed to the joist tops will effectively act
as a diaphram and provide strength. Buy insulation at ENCON for best
rates.

insulating then boarding an attic - is it worth increasing joist depth first?
 

On 16 Oct, 16:38, AJH wrote:
On 16 Oct, 00:21, wrote:

Looking to board my attic for storage; it has some scrappy Rockwool
and joists are 4"x2". I was wondering whether to plant 2"x2" timbers
on joists to allow for greater depth of Rockwool, or maybe the
chipboard would provide enough extra insulation? Another thought -
better grade insulation material in place of Rockwool but in the same
4" space? Any ideas welcomed.

It sounds as if you are asking 2 things:
1) boarding the loft
2) insulating the ceiling against heat loss

The best way to insulate your ceiling is at ceiling joist level not at
rafter level, that is for loft conversions.
4x4 joists should be fine for general storage as long as they are at
400mm crs and not overspanned. Heavier loads should be kept over load
bearing walls or near the joist ends.
If you have plasterboard ceilings you will have virtually 100mm depth
available so drop in 90mm Celotex, Xtratherm Ecotherm or similar
ridgid boards cut as a good fit between the joists. To seal any slight
gaps run aluminium tape across the top of the joists overlapping onto
the boards, it's fairly cheap for a 100mm wide roll. The just lay
boards over. Don't use MDF as it is heavy, go for building ply, it's
light and strong and if screwed to the joist tops will effectively act
as a diaphram and provide strength. Buy insulation at ENCON for best
rates.

I agree with AJH who had a better solution than mine
Chris

insulating then boarding an attic - is it worth increasing joist depth first?
 

On Oct 16, 7:42 pm, wrote:
On 16 Oct, 16:38, AJH wrote:





On 16 Oct, 00:21, wrote:

Looking to board my attic for storage; it has some scrappy Rockwool
and joists are 4"x2". I was wondering whether to plant 2"x2" timbers
on joists to allow for greater depth of Rockwool, or maybe the
chipboard would provide enough extra insulation? Another thought -
better grade insulation material in place of Rockwool but in the same
4" space? Any ideas welcomed.

It sounds as if you are asking 2 things:
1) boarding the loft
2) insulating the ceiling against heat loss

The best way to insulate your ceiling is at ceiling joist level not at
rafter level, that is for loft conversions.
4x4 joists should be fine for general storage as long as they are at
400mm crs and not overspanned. Heavier loads should be kept over load
bearing walls or near the joist ends.
If you have plasterboard ceilings you will have virtually 100mm depth
available so drop in 90mm Celotex, Xtratherm Ecotherm or similar
ridgid boards cut as a good fit between the joists. To seal any slight
gaps run aluminium tape across the top of the joists overlapping onto
the boards, it's fairly cheap for a 100mm wide roll. The just lay
boards over. Don't use MDF as it is heavy, go for building ply, it's
light and strong and if screwed to the joist tops will effectively act
as a diaphram and provide strength. Buy insulation at ENCON for best
rates.

I agree with AJH who had a better solution than mine
Chris

A bit of a U-turn from "To get storage on this you will need blocks
on the joists close to the bearings and run bigger joists on top -
quite expensive and not a good structural solution and even then
limited to loading

to get a good loading you need a good well-engineered structure"

MBQ