Insulating the rafters of old state house

Forums › Home Workshop DIY › Insulating the rafters of old state house

madmanzippy

9 posts

Wannabe Geek

#289129 14-Aug-2021 12:30

Hi all, We have an ex state house that has the concrete tile roof with no building paper underneath. I am wanting to make this house a bit warmer and not be losing all that heat. We do have a mixture of pinkbats and macerated paper type fill on the ceiling but during winter you can feel a bit of moisture up there and of course the wind howls through. Plenty of standing space.

My thoughts are:

Put building paper between the rafters and fix it in place with batterns running the length of the rafter and then polystyrene over that.

Do the building paper (as above) and just sheets of ply or gib or similar to line it all.

Anyone done this before or want to chip in?

Thanks

vexxxboy

4245 posts

Uber Geek

#2759991 14-Aug-2021 13:59

have you checked out Govt. insulation subsidies , if you qualify, the Govt will pay at least 80% and sometimes up to 90% of replacing your insulation. Basically if your house is old and you live in a low income area or have a community card then you will get it.

Common sense is not as common as you think.

timmmay

20589 posts

Uber Geek

Trusted

Lifetime subscriber

#2759994 14-Aug-2021 14:42

I thought building paper was for waterproofing. I goes directly under the tiles / iron so any water that gets through runs out to the guttering. If you can run up near the tiles, sure.

For insulation, standard pink batts as thick as you like. If you have moisture I'd look for the source. If it's from above the building paper should help.

madmanzippy

9 posts

Wannabe Geek

#2760002 14-Aug-2021 15:37

Here are a couple of pics so you can see my dilemma. When it pours down and the wind is in the right direction, moisture gets in. It is not wet, but it is just damp. We have stuff stored up there including photos, and none of it is damaged, so not that bad. I just want to sort it. Could i just stuff pinkbats in the gaps of the rafters? Thinking about the building paper idea. If I have the paper there, then that is going to catch water and concentrate it and possibly pool or soak the wood. If i have pinkbats jammed hard against the tiles it won't allow the moisture in and the wind will keep it breathing and dry? possibly? I am just trying to avoid a $30k or $40k roof job.

timmmay

20589 posts

Uber Geek

Trusted

Lifetime subscriber

#2760006 14-Aug-2021 15:59

No, you can't jam anything up by the tiles. Get a roofer in, and avoid storing things up there. I'd probably re-roof but maybe someone else has a better idea.

Bung

6496 posts

Uber Geek

Subscriber

#2760008 14-Aug-2021 15:59

If the wind howls through then insulating directly under the tiles is pointless. The usual approach would be improving the insulation over the ceiling including a layer above the joists. If you still have concrete roof tiles you could be on the verge of needing a reroof.

Our old house in Wellington was ex State 1940s. The roof on that was end of life. Once the colour layer has gone (yes they weren't all grey originally) wind and rain wears the tiles down and fills the gutters with sand. You could find that a couple of days rain will saturate the tiles and they will drip water. The odd tile will also split as they get thinner.

Edit: just seen the photos. What was going on that required the rafters to be doubled up?

madmanzippy

9 posts

Wannabe Geek

#2760014 14-Aug-2021 16:53

House was relocated, so half the roof was dropped. Tiles are in good condition as the have a coloured rubbery paint on them.

k1w1k1d

1528 posts

Uber Geek

#2760069 14-Aug-2021 17:42

Apart from the extra rafters it looks just like the roof in our 1950's house. The airflow through the roof space should dry any moisture out.

Every few years we just get the roof moss proofed and then the following year we get it silicon sprayed to make it waterproof.

We also put Terra Lana R1.8 biscuits between the joists over the shrunken batts that were already there. We then put Terra Lana R1.8 roll over the top which covers the joists.

Quic Broadband

Move to New Zealand's best fibre broadband service (affiliate link). Free setup code: R587125ERQ6VE. Note that to use Quic Broadband you must be comfortable with configuring your own router.

neb

11294 posts

Uber Geek

Trusted

Lifetime subscriber

#2760070 14-Aug-2021 17:48

Nothing much to add beyond what others have already said, but just a general comment, if you've got problems with moisture up there then during the re-do get the paper fluff sucked out, that stuff just sucks up moisture and then you run into problems with mould and mould spores...

SATTV

1648 posts

Uber Geek

ID Verified

#2760075 14-Aug-2021 18:41

I am in the same boat but with a lot less headroom.

I was thinking of just putting building paper on the underside of the joists, this will prevent any moisture.

Being that the house was relocated the roof would have had to have come off, the relocation / builders that put it back together should have put paper up. I dont know how it got signed off like that.

When was it moved?

John

I know enough to be dangerous

madmanzippy

9 posts

Wannabe Geek

#2760083 14-Aug-2021 21:07

Thanks everyone. As i say, things tend to be ok up there, and it is only the old paper stuff that tells me there is moisture. The ducted heatpump is great, but thought that if I could somehow insulate the roof also, it would be even better. I think I may be introducing problem without doing it properly.

madmanzippy

9 posts

Wannabe Geek

#2760084 14-Aug-2021 21:10

It was moved about 4 years ago, but only about the top 3rd of the roof was dropped.