Laying ground plastic under house question

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Ultimate Geek

#2693950 16-Apr-2021 19:43

Eva888: Thanks, the consensus seems to be to lay the vapour barrier.

We will also be replacing underfloor insulation after the plastic is laid as the present one is that silver tar paper stuff of the 70s. No idea how that’s going to work out since there is now heating ducting, wires and all sorts under there. The crawl space is very low to the ground in parts to complicate matters.

Be careful, there are situations where the foil can be live and you can get electrocuted. This foil insulation is now banned and can’t be repaired/replaced.

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Kickinbac

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Ultimate Geek

#2693952 16-Apr-2021 19:48

timmmay:
I wonder if a vapor barrier can be attached to the bottom of the floorboards rather than over the ground if it's really wet down there.

A few years ago there was an installation product being sold that was like a foil faced bubble wrap. This was rolled out and stapled under the joists providing insulation, air and moisture barrier. Not sure if still available.

tchart

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#2693958 16-Apr-2021 20:36

We had this done when we installed under floor insulation under our 1980s Lockwood. Made a massive difference. Was always nice and dry under the house after it was installed.

mentalinc

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#2694028 16-Apr-2021 22:09

Consider working out where the water is flowing from and maybe putting in some drainage to limit the water engress

But still do the vapor barrier.

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Kickinbac

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Ultimate Geek

#2694079 17-Apr-2021 09:54

Kickinbac:
Eva888: Thanks, the consensus seems to be to lay the vapour barrier.

We will also be replacing underfloor insulation after the plastic is laid as the present one is that silver tar paper stuff of the 70s. No idea how that’s going to work out since there is now heating ducting, wires and all sorts under there. The crawl space is very low to the ground in parts to complicate matters.

Be careful, there are situations where the foil can be live and you can get electrocuted. This foil insulation is now banned and can’t be repaired/replaced.

Found this on Consumer... Sorry a little off topic but thought I needed to add some information.

‘Foil has been used for many years for underfloor insulation. A ban on the installation of foil insulation into residential buildings, and the repair of existing foil insulation, came into force on 1 July 2016.
Since 2005, five people have died after being electrocuted when foil insulation they were installing came into contact with electrical wiring.’

Good advice is to turn off the power when working around foil insulation.

Eva888

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#2694137 17-Apr-2021 11:03

Kickinbac:
Eva888: Thanks, the consensus seems to be to lay the vapour barrier.

We will also be replacing underfloor insulation after the plastic is laid as the present one is that silver tar paper stuff of the 70s. No idea how that’s going to work out since there is now heating ducting, wires and all sorts under there. The crawl space is very low to the ground in parts to complicate matters.

Be careful, there are situations where the foil can be live and you can get electrocuted. This foil insulation is now banned and can’t be repaired/replaced.

The thing one learns. Thanks, who would have thought of this. Should they be removing the foil to put the other insulation or just go over it?

Eva888

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#2694138 17-Apr-2021 11:10

Now am worried because of the tight space and the wires for heating and other wiring under the house, yes will definitely turn off the power which means pitch black under there. Thank goodness this was mentioned. Will need to buy some sort of portable lighting. Am so glad I asked about this as the young guy doing this is not a professional firm per se but has been doing it for a few people we know. He’s coming on Monday so I need to have the lighting bought. Any suggestions for this?

mdf

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#2694139 17-Apr-2021 11:40

Eva888: Now am worried because of the tight space and the wires for heating and other wiring under the house, yes will definitely turn off the power which means pitch black under there. Thank goodness this was mentioned. Will need to buy some sort of portable lighting. Am so glad I asked about this as the young guy doing this is not a professional firm per se but has been doing it for a few people we know. He’s coming on Monday so I need to have the lighting bought. Any suggestions for this?

I've been the person tasked with crawling under my relatives' houses and in claustrophobic spaces (can't crawl, can't roll over, drive forward with your toes). First hand experience: having the light go out deep in the bowels of darkness is no fun at all.

Head torch is by far and away the best option. Doesn't use up an extra hand and it will shine where you need to see. These ones are really good and competitively priced: https://www.bunnings.co.nz/arlec-300-lumen-led-head-torch-with-hard-hat-compatibility_p4410939

I would imagine anyone that has done this more than once has his/her/their own kit already, but FWIW my under the house kit is:

- kneepads - crawling on rocks is no fun otherwise

- work gloves

- overalls

- beanie - you will want to lie your head back at some stage and you don't want to have to figure out what will end up in your hair as a result

- safety glasses - if you're looking up, I guarantee dust will fall in your eye, especially from existing insulation

- head torch

- pull along - I use a sturdy shallow bin with a bungee I can clip and unclip. Way better than a toolbox or toolbelt for the tools you will need.

- mask/respirator (depends what you're doing)

- leaf blower - for de-filthing and un-bugging afterwards.

BTW, +1 for what others have said about polythene generally. Dirt being dry isn't a good sign - it means the moisture is going somewhere which is almost certainly your house.

Jase2985

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#2694143 17-Apr-2021 12:05

also tape up your leg and arm sleeves with electrical tape. stops crap going up there.

Eva888

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#2694144 17-Apr-2021 12:12

@mdf thanks for the great list. The young chap is still at Uni and I don’t think he has all the stuff you suggest so I will get it for him. Didn’t think of safety glasses. For other tradies that have to slither I bought a number of meters of plastic carpet protector from Bunnings that has grips underneath so they could slide on that instead of the dirt. I will be glad when this is over and look forward to no more musty smells.

Bung

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#2694145 17-Apr-2021 12:31

Worth reading. Includes the underfloor plastic.

NZS 4246:2016
CURRENT SPONSORED Date published: 30/08/16

Energy efficiency - Installing bulk thermal insulation in residential buildings

Standards New Zealand offers this standard in hard copy, or as a PDF with a single user, single print licence to download and save onto a personal computer. Tenancy Services have available the option to view and print a single copy at no charge, on their website at www.tenancy.govt.nz

Kickinbac

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Ultimate Geek

#2694273 17-Apr-2021 18:41

+1 for the head torch. Plus have a strong led torch for general illumination. You can pick up a dolphin torches for about $30, these now have led bulbs.
If your neighbours are close enough you could ask to run a power lead and plug in a worklight.

If the earth is smooth, lay out the polythene in the easiest areas first, cloest to entrance. Its easier and cleaner to slide around on this. You just dont want to risk puncturing it on sharp stones etc. any holes can be taped up if you know where they are.

P.S. a few years ago I installed Expol under my 60’s house. It had unevenly spaced rough sawn joists. I’d never do that again as was such an awkward PITA. If it had dressed joists it would have been easier.
I’d look at polyester roll insulation like greenstuff.

mdooher

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#2694288 17-Apr-2021 20:00

Eva888: Now am worried because of the tight space and the wires for heating and other wiring under the house, yes will definitely turn off the power which means pitch black under there. Thank goodness this was mentioned. Will need to buy some sort of portable lighting. Am so glad I asked about this as the young guy doing this is not a professional firm per se but has been doing it for a few people we know. He’s coming on Monday so I need to have the lighting bought. Any suggestions for this?

Don't worry yourself too much. Those that got shocks installing the foil lined stuff shot staples through the foil and into the wiring. 😲 That was only ever going to be bad. I actuality installed some of that back in the day and you just had to do a good survey before starting.

Anyway it is extremely unlikely that if the stuff is not live now that it will become live while you are under there. But having said that if you feel better turning off the power then do it.

Back to the membrane... I had a house that was so wet underneath we jacked each bearer off the pile and slid in ether a bit of ice cream container or a bit of malthoid. Did it help? who knows but everything sure dried out, I got good at fixing squeaking floor boards as the place dried out.

Matthew

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#2694297 17-Apr-2021 20:37

Add to the list: A can or two of bug spray. Having swarms of ants crawling all over you as you try and work is not fun.

neb

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#2694302 17-Apr-2021 21:02

mdooher:
Back to the membrane... I had a house that was so wet underneath we jacked each bearer off the pile and slid in ether a bit of ice cream container or a bit of malthoid.

I assume it's an older house, because any newish build would have to have the malthoid already fitted?

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