Child Item

How to add a subfloor ground moisture barrier?

Hello,

I want to place black plastic polythene under my subfloor. The plastic needs to go on top of the ground to keep the moisture from effecting hardwood floors that we are planning to install. I have no idea if there are companies in Sydney that are able to do the installation? I've started laying one row but the space is quite tight and probably needs someone a bit smaller that has the patience to do the work. Any ideas how I can 'google' and find tradies / companies that can do the work?

Link to a site in New Zealand that speaks to the works I need to do:
https://www.ecodesignadvisor.org.nz/resources/ground-moisture-barriers-guide-installation/

Thanks so much!

Find more posts tagged with

Tools and Materials

Renovation

Building and Construction

Flooring

Comments

JacobZ

Hi @Chrismichael,

Welcome to the Bunnings Workshop community, it is great to have you with us.

The three types of businesses that I can think might be able to assist you with this kind of job are handymen, landscapers and water proofers.

While none of these specialise in this exact style of project, I'm sure they would undertake similar work and would have the knowhow to be able to help.

You might like to use a service like Hipages or Airtasker to search for someone to do this job. I would advise taking some photos and giving as much detail as possible to ensure someone answers as quickly as possible.

If you wanted to try and take on the job yourself, I'd suggest getting GRUNT 2 x 100m Black 70um Multi Use Plastic Film, Grunt Builders Film Tape, and a headlamp.

If you have any other questions, please feel free to get in touch.

Jacob

Chrismichael

https://www.workshop.bunnings.com.au/discussion/comment/36689#Comment_36689

Thanks Jacob for your suggestion,

I reached out to a few companies and heard back from one that specialises in waterproofing and subfloor ventilation. The moisture barrier is something they have installed in the past and are familiar with, just not something they advertise.

Thanks for leading me in the right direction!

Chris

farnie

https://www.workshop.bunnings.com.au/discussion/comment/80585#Comment_80585

Did you find that the moisture barrier was effective at reducing moisture in your house? I am considering doing the polythene barrier myself

JacobZ

https://www.workshop.bunnings.com.au/discussion/comment/109592#Comment_109592

Hi @farnie,

A warm welcome to the Bunnings Workshop community, it's wonderful to have you with us.

Please allow me to tag @Chrismichael so they are notified of your question.

If done well, I am sure the moisture reduction would be fairly significant, but hopefully, they will respond shortly with their experiences.

Jacob

Chrismichael

https://www.workshop.bunnings.com.au/discussion/comment/109592#Comment_109592

Hello, I did get a hold of a company that could place the barrier but they declined because of the tight clearance height in the crawl space. Unfortunately I had to complete it myself. I used the heavy black sheeting and taped the overlaps.

I also had ducted ventilation installed that runs on a timer. The ventilation probably does alot to remove the moisture below. We haven't had any issues with our hardwood floors expanding or cupping and its been nearly a year since installation.

I wouldn't say that the barrier noticeably stopped moisture coming into the house however. It reduces the moisture that otherwise would enter the floorboards and the hardwood floors directly above it.

Hope that helps

EricL

https://www.workshop.bunnings.com.au/discussion/comment/122147#Comment_122147

Hello @Chrismichael

Thank you for providing that extra information in regards to your ground moisture barrier. Let me tag @farnie to make them aware of your answer.

Eric

FrivolousPanda

https://www.workshop.bunnings.com.au/discussion/comment/122147#Comment_122147

Hi @Chrismichael,

I am looking into doing the same with my subfloor.

What did you do at the wall? Run the plastic up 50mm and tape it? What tape did you use?

Thanks

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/130209#Comment_130209

Welcome to the Bunnings Workshop community @FrivolousPanda. It's brilliant to have you join us, and many thanks for your question about moisture barriers.

Let me tag @Chrismichael so they are alerted to your question.

Have you considered stapling a moisture barrier to the underside of your floor joists?

Please let me know if you have any questions.

Mitchell

Chrismichael

https://www.workshop.bunnings.com.au/discussion/comment/130209#Comment_130209

Hello, I used the same products that Bunnings recommend earlier in the thread..I ran the plastic up the wall and around any posts etc...by about six inches or so. The tape I used is below.

Tape

Thanks

EricL

https://www.workshop.bunnings.com.au/discussion/comment/135199#Comment_135199

Hello @Chrismichael

Thank you very much for providing that information. Let me tag @FrivolousPanda to make them aware of your recommendations.

Eric

FrivolousPanda

https://www.workshop.bunnings.com.au/discussion/comment/135195#Comment_135195

Hi Mitchell,

Regards to your idea of stapling the plastic to the joists, I have a double brick house with some brick vents on the external walls. If I stapled the plastic to the joists it would cover these vents up or at least prevent the air under the floorboards circulating with outside air.

I'm not sure if that is a good or bad thing.

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/138522#Comment_138522

I guess that depends on where the moisture is coming from that you want to exclude @FrivolousPanda. The air vents are to allow the area under the house to dry out, rather than the floorboards themselves. If you do a lot of wet mopping of the floorboards, it might not be a good idea to seal under them. However, moisture barriers come in one-way designs. So, moisture can't penetrate through them from underneath to reach the joists, but any moisture in the joists can penetrate out into the area under the house, allowing them to dry.

Mitchell

Child Item