Laying ground plastic under house question

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#2694308 17-Apr-2021 21:30

I think it is only required if the pile/bearer interface is lower than 300mm from finished ground level (150mm min).

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Eva888

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#2694383 18-Apr-2021 12:53

House is 1978. Yes I think that silver stuff was called malthoid.

Slightly off topic though in the same space, the malthoid will need to be removed to put in underfloor batts. Under the house wires are attached to bearers and joists so I foresee difficulty in placing the new batts. I suspect that’s when the real danger would be in accidentally stapling onto a wire. He’s coming to prep the area tomorrow to remove sharp stones etc and I’m thinking it would be a good time to also raise some of the heating ducting that’s hanging onto the ground in places. I objected at the time of installation but got the rolling eyes look and was told it was no problem where they were touching the ground. Am truly not looking forward to any of this.

Kickinbac

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#2694391 18-Apr-2021 13:53

Eva888: House is 1978. Yes I think that silver stuff was called malthoid.

Slightly off topic though in the same space, the malthoid will need to be removed to put in underfloor batts. Under the house wires are attached to bearers and joists so I foresee difficulty in placing the new batts. I suspect that’s when the real danger would be in accidentally stapling onto a wire. He’s coming to prep the area tomorrow to remove sharp stones etc and I’m thinking it would be a good time to also raise some of the heating ducting that’s hanging onto the ground in places. I objected at the time of installation but got the rolling eyes look and was told it was no problem where they were touching the ground. Am truly not looking forward to any of this.

Malthoid is a black tar type paper, used between concrete and timber to stop moisture getting into the timber. These days called damp proof course (DPC) and now commonly a dimpled plastic strip.
Silver paper is just silver paper.
For hanging the ducts, you can use the blue plastic carton straping. If you are resourceful and know where they deal with packaging you can recover lots of it for free. Lets just say the dumpster behind your local harvey norman etc. Often they have the metal or plastic buckles too. Can be bought at warehouse stationary too. We usually use a silver cardboard saddle to spread the load to stop the duct crushing.

Eva888

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#2694409 18-Apr-2021 14:50

Kickinbac:
Eva888: House is 1978. Yes I think that silver stuff was called malthoid.

Slightly off topic though in the same space, the malthoid will need to be removed to put in underfloor batts. Under the house wires are attached to bearers and joists so I foresee difficulty in placing the new batts. I suspect that’s when the real danger would be in accidentally stapling onto a wire. He’s coming to prep the area tomorrow to remove sharp stones etc and I’m thinking it would be a good time to also raise some of the heating ducting that’s hanging onto the ground in places. I objected at the time of installation but got the rolling eyes look and was told it was no problem where they were touching the ground. Am truly not looking forward to any of this.

Malthoid is a black tar type paper, used between concrete and timber to stop moisture getting into the timber. These days called damp proof course (DPC) and now commonly a dimpled plastic strip.
Silver paper is just silver paper.
For hanging the ducts, you can use the blue plastic carton straping. If you are resourceful and know where they deal with packaging you can recover lots of it for free. Lets just say the dumpster behind your local harvey norman etc. Often they have the metal or plastic buckles too. Can be bought at warehouse stationary too. We usually use a silver cardboard saddle to spread the load to stop the duct crushing.

Thanks for the pictures, that looks very sensible, unlike what my installers did which was use thin cable ties that crushed the ducting and in some places they shoved it above the joist totally crushing it. You have to wonder about some trades. I like the cradle idea and could also make some out of yoga mat material. Wish I had more time to prepare as he comes tomorrow. I will show him the picture so he gets the idea. Many thanks for that.

My silver stuff has black in between the silver layers. Must take a photo under the house to show the before. Am also slightly concerned about the way the piles are wired to the joists and wanted to add those z fixings everyone talks about. Sure it’s been standing fine through so many quakes but now that I’m down there all the time, I’m noticing everything with new eyes. Eternal optimist Mr E says not going down there is the answer. ~_^

Bung

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#2694491 18-Apr-2021 16:30

Are they timber or concrete piles? If timber any wires would be doing the job of z nails already.

larknz

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#2694499 18-Apr-2021 17:03

The silver stuff is called Sisalation and is a bit more than just silver paper. The main purpose was to reflect radiant heat. It's insulation value was not great.

Eva888

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#2694514 18-Apr-2021 18:34

Bung: Are they timber or concrete piles? If timber any wires would be doing the job of z nails already.

Concrete with a wire either side.

Bung

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#2694532 18-Apr-2021 20:12

The Wellington city council was promoting a Pryda earthquake resilience kit for concrete piles that appeared to be repurposed concealed purlin cleats. They don't seem available now, probably weren't a big seller but you could get the bits separately.

Eva888

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#2694789 19-Apr-2021 13:30

Fantastic chap seems to know what he’s doing and is finding all sorts of issues. One causing water is the heating unit's outflow hose just left to pour out over the dirt. That explains why winter when the heating is always on there must have been quite a bit of water and thus the musty smell. I have no idea how much water it would be, but for the moment will have it going into a bucket until a plumber can attach more hose and send it out of the under house area. It angers me that installers can do such things. Does anyone have any idea of the amount of water that comes out of a unit?

Much of the ducting is lying on the ground so I’ve bought yoga mats $6 from the Warehouse to cut up for cradles and cable ties can go over the cradles to lift them.

The best news...he came upstairs and showed me a beautiful ring I had inherited and that had been lost for years. He saw it lying on the ground glittering from his torchlight and we have no idea how it got there. Will definitely give him extra as a reward for being so honest. He could easily have pocketed it.

neb

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#2694820 19-Apr-2021 14:59

Eva888: I have no idea how much water it would be, but for the moment will have it going into a bucket until a plumber can attach more hose and send it out of the under house area.

It's normal for it to drip a bit when heating, but shouldn't be running continuously... if it is, get the plumber to take a look when they do the other work you're referring to. In particular to check for a pressure issue, turn of the power for a bit (i.e. stop the heating) and see if the flow stops. If not, get it looked at sooner rather than later.

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#2694833 19-Apr-2021 15:50

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.

Yip. In our first house we did Expol. What a PITA, especially when the house moved and sheets fell out. TPS doesn't like it at all and you have to wrap it in paper.

The second house we had done with polyester. It's great stuff and has the benefit of being easy to move and work with.

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#2695200 20-Apr-2021 11:10

I need that beating head against wall emoji! Went downstairs job almost finished. He has put the plastic barrier over the top of aerial cables and the latest white fibre one chorus put in, so the cables are under the plastic and on the ground where I’m concerned moisture can build up. Unless he undoes all the work from one end of the house to the other, the only way is to pull them both out from the source and start over.

Meanwhile...before the ground barrier idea, I had bought 17 meters of that heavy clear 1 meter wide plastic carpet protector which I was going to have laid over the ground so that plumbers etc could slither on that instead of on the dirt. It’s really low to the ground don there. Now we have laid the black plastic which is joined in places and sure you can slither over, but it will get pulled at the seams and damaged from stones underneath. So...I want to lay the carpet protector over the plastic on a path taken by the tradies.

Problem is, it has little spike grips underneath which was perfect on the dirt but now these would need to be flattened first so they don’t poke into the black plastic on the ground. Any ideas what I can use to flatten them. Am thinking of my iron, over tinfoil over the spikes. Not the greatest thing for my iron though. Any other suggestions?

Eva888

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#2695208 20-Apr-2021 11:23

Nope...that idea didn’t work. Flattened spikes got jagged edges after ironing and were just as rough. Would have to lay something over the underside and spikes, some sort of thin firm foam material which also may add some grip. Any thoughts on what could be used?

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#2695517 20-Apr-2021 23:08

Eva888: Nope...that idea didn’t work. Flattened spikes got jagged edges after ironing and were just as rough. Would have to lay something over the underside and spikes, some sort of thin firm foam material which also may add some grip. Any thoughts on what could be used?

There is a rubberized mesh that you put under rugs and mats that are placed on wood or vinyl floors to stop them slipping and sliding.
Also used in kitchen utensil drawers to stop utensils sliding about.
Comes in rolls 60cm wide. Maybe not a Bunnings product.
I think I got our last batch at a 2$ shop.

neb

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#2695526 21-Apr-2021 01:20

In terms of limiting how much more money you throw at it, tarps are about the cheapest material you can buy in large sizes that probably do what you want, just get one of those and cut it into strips. I looked at this problem for drip protection for painting and anything else, including stuff you'd think was cheaper, costs more than that. To hold them in place, use masking tape if you need to remove them later, otherwise duct tape.

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