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Cheap and easy way to insulate underfloor of weatherboard house

Hi,

I have an old weatherboard house and would like to get under the house and install insulation under the floor.

I have very little headroom (less than 1m) under the house so I think struggling with stiff boards is not an option.

So I am looking for a simple and cheap method to do this. It does not have to be super insulation - just enough to take the edge off somewhat and something I can buy in-store.

Also, hints on what tools I would need would be greatly appreciated too,

Many Thanks

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Building and Construction

Heating and Cooling

Flooring

Comments

MitchellMc

Hi @TimD,

What type of internal flooring do you have? Knowing this will help our members determine what type of underfloor insulation will help take the edge off and allow them to offer some great solutions.

It sounds like you have a very similar situation to mine as there is not much headroom to work in either. I have old timber floorboards, and the gaps in them allow the ambient air to flow through into the house. In my case, GI Building Sciences 1.35m x 22.5m x 4mm Reflecta Cell Floor Insulation or Ametalin 500mm x 60m ThermalFloor Reflective Underfloor Insulation would be effective as it would block that airflow. However, if your floor structure is conducting the cold and heat through it, then Bradford R2.5 1160 x 415 x 90mm 4.2m2 Optimo Underfloor Insulation - 8 Pieces might be a more viable solution.

I'll be keen to hear what type of floors you have. I might join you on this project as I'm not looking forward to the cold temperatures that we'll see shortly.

Mitchell

TimD

https://www.workshop.bunnings.com.au/discussion/comment/12948#Comment_12948

Hi Mitchell,

Thanks for the quick reply. Sorry I should have said...

It is old timber flooring and similar to your situation by the sound of it. They sit less than 1m above the ground, ie there is nothing between the floorboards and the bare earth. There are small gaps between the boards which do let the cold breeze in also.

The Reflecta cell floor and Ametalin look like the kind of thing I would be interested in however they appear to be special order only. If I went for this solution, I'm guessing I would also need to purchase a staple gun? I assume an office stationery staple gun would not do the trick and would need to be more heavy duty for the joists?

Thanks - any further recommendations from you or the community would be most welcome.

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/68949#Comment_68949

These products are available through our Special Orders, and I would be happy to assist you with the ordering process @TimD.

I would suggest using an Arrow T50 Heavy Duty Staple Gun as lighter-duty units will have difficulty penetrating the hardwood joists. I recently used a budget-friendly staple gun to fix into softwood, which caused plenty of frustration, so I would advise using a premium product instead.

You might be interested in reading through these previous discussions: Insulating an old house on a budget by @JDE and Underfloor insulation by @Diannelin.

You should find these step-by-step guides useful: How to install underfloor insulation batts and How to install underfloor foil insulation. You'll be positioning your insulation from underneath, but there is still plenty of helpful information within them.

Mitchell

JDE

https://www.workshop.bunnings.com.au/discussion/comment/97442#Comment_97442

TimD

We recently did this. Yes it definitely had an effect. Not as much as doing the ceiling. As Mitchell said watch some of the bunnings videos https://www.bunnings.com.au/our-range/brands/e/earthwool. I was on similar height restrictions. Just some things we found.

Make sure you wear long sleaves , gloves- long ones and a face mask/ goggles (safety glasses didnt cut it) you will be laying up close and under the bats. If you do get the itch cold shower first not hot you dont want to open pores any more than necessary

Unless you are particularly strong in hand I suggest an electric stapler we bought a ryobi one stapler excellent - you will be putting in hundreds of staples.

Knee pads were great the builder left me lots of rubble

A good flood light and a decent pair of large scissors

Floor insulation is different to ceiling bats they are stiffer to reduce sag and some have a membrane on one side (we used this and got it from Bunnings)

Make sure you use plenty of strapping as it will ensure less sagging as bats swell

Dont forget insulation comes in different widths so make sure you get the right one to reduce wastage.

Not a fun job but in our case definitely helped

JDE

tibz_timber

https://www.workshop.bunnings.com.au/discussion/comment/115387#Comment_115387

Hi @JDE

Were your floor joist hardwood or treated pine? Interested in knowing how the Ryobi stapler handles hardwood.

Tibz

TimD

https://www.workshop.bunnings.com.au/discussion/comment/115387#Comment_115387

Thanks @JDE for the tips.

I have just ordered the GI Building Sciences 1.35m x 22.5m x 4mm Reflecta Cell Floor Insulation (thanks for the tips @MitchellMc )

JDE, yes i was thinking I would just buy the Arrow stapler. I did consider the Ryobi to add to my "collection" but I am not sure I would get much use out of it after this job. I may yes still change my mind. With the Ryobi, do you just buy ordinary T50 staples like these Arrow? https://www.bunnings.com.au/arrow-8mm-t50-staples-1250-pack_p5911777 I am thinking as the Reflecta cell is only 4mm thick I probably only need the 8mm staples. The joists are 100 years old and rock hard, so I don't want too long staples to drive in I would think.

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/125559#Comment_125559

Hi @TimD,

The Ryobi 18V ONE+ Cordless Stapler is designed to be used with T-50 Staples, which have a staple size of 10 mm (3/8”) and a length of 6 mm - 14 mm (1/4” - 9/16”). The Arrow 8mm T50 Staples would be suitable for use in this tool.

Mitchell

JDE

https://www.workshop.bunnings.com.au/discussion/comment/125559#Comment_125559

Tim

The ryobi uses standard staples I ended up buying Ithink they were craft light ones from Bunnings. Sorry my wife has pinched it as she uses it when upholstering chairs etc. We used 8mm stapes from memory and yes it was into 50 year old cyprus worked well if you turned it up (it has adjustable drive) and held it tight against timber

JDE

tibz_timber

https://www.workshop.bunnings.com.au/discussion/comment/132401#Comment_132401

@JDE

Was asking as my Ryobi 18GA brad nailer struggles with Australian hardwoods? Yes, it will handle hardwood if it is clean and properly adjusted for a couple of hundred nails but then it needs maintenance and adjustment again. Can get a little frustrating at times. Just hoping the stapler was less temperamental.

Tibz

TimD

Hi All,

A quick update. After several weekends, I have now completed my insulation!

A few lessons learned :-

Don't underestimate the amount of material needed - I had to double my order. Also staples - will need more than you think. I used GI Building Sciences 1.35m x 22.5m x 4mm Reflecta Cell Floor Insulation. The good thing about this was its like material, easy to cut and flexible and easy to staple. It was special order, but took less than a week to arrive
It will take longer than expected! Don't try and do it in one go. The space under my house was very limited - in some places less than 0.5m - so a lot of crawling on my back for hours at a time
Watch out for electric cables - there are more cables under your house than you expect and of course be very careful
Buy a battery electric stapler. I did hesitate at first thinking it was extravagant for one job, but there is no way I could have done it with a manual stapler. I used the Ryobi 18V ONE+ Cordless Stapler and Arrow 10mm T50 staples. It did jam a few times at the start but later not at all. Maybe it was my technique
Remember goggles and mask - a lot of dust under the house
Remember ear protection - the electric stapler is not particularly loud, but you are in an enclosed space stapling for hours and could cause damage
Wear a cap or other head protection. You will bump your head!

Other tools:

Sharp knife and metal ruler to cut the insulation before going under the house
Scissors to cut around pipes, cables etc.
Tape to join/seal the pieces - don't allow gaps for the draft to get in
Tape measure - measure between each joist - I was surprised just how much the gaps between them varied from joist to joist - some were also not parallel (old house)
Marker pen to mark the size of each strip. The more you can plan before going under the house the better
Chalk to label between joists and their sizes
Torch and headlamp so you can see clearly any obstacles especially cables hiding in corners and along joists. Check, then check again
Box to take all the tools you need at the start of the job so you don't have to keep crawling back out from under the house. Use tool, put back in box, not on the ground. I lost 2 pairs of scissors by not doing that (found them again)
Use an old yoga mat to lie on - lots of rocks and rubble under the house
Old clothes you don't mind ruining
Probably most important - Bath salts. These are for a long soak after a day of crawling around in dust, dirt, rocks and cob webs 😀

Thanks everyone who contributed to my post and special thanks to the moderator @MitchellMc who provided the list of suggested products. Without tips and suggestions from everyone, I probably would not have had the confidence to embark on this little project,

Thanks again

Tim

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/13412#Comment_13412

It's fabulous to hear that your project was a success @TimD! We really appreciate the time you've taken to thoroughly explain the steps you took and the equipment needed. They will be extremely beneficial to the next member considering a similar project.

I now look forward to your feedback on the difference the insulation has made. I suspect we might need to wait a little while for that update.

Many thanks for sharing your success.

Mitchell

Jason

https://www.workshop.bunnings.com.au/discussion/comment/13412#Comment_13412

Just wanted to add my thanks for coming back and sharing your experiences and lessons learned @TimD. I'm sure Bunnings Workshop members will find this extremely helpful when tackling a similar job in the future.

Thanks again,

Jason

Sally8

https://www.workshop.bunnings.com.au/discussion/comment/69220#Comment_69220

I have read this thread and think the advice in it is great. I too have an old house with a timber floor and a ~600mm crawl space underneath and I am trying to resolve an issue. I am just not sure which product to use and would love some advice. The ground underneath is bare earth which does get slightly damp in high rain, the floorboards are hardwood. Inside the room(s) it is very cold in winter and damp. The pillows on the bed are often damp and the ceiling has mould and the clothes in the wardrobes get mouldy too. Would I be better off using the foil or insulation bats (Earthwool) and if so what rating? Sound proofing is not an issue. Many thanks in advance for any advice.

StevieB

https://www.workshop.bunnings.com.au/discussion/comment/97825#Comment_97825

Welcome to the Bunnings Workshop community @Sally8 and thanks for reaching out with your question. It's great to see you jump straight in and contribute to this discussion.

Let me tag @TimD and @JDE who may be able to offer suggestions. Our resident D.I.Y. expert @EricL will also be happy to help when he's back on the site on Friday.

Stevie

TimD

https://www.workshop.bunnings.com.au/discussion/comment/115598#Comment_115598

Hi @Sally8,

I can't advise on which would be the better option for you. Our house too has bare earth underneath. If it rains the first 20cm or so of the soil is damp but once under the house proper the earth is very dry. Yes, if we are having a rainy period the house feels a little damp but luckily we don't have mould. The big thing for me was that the foil was very easy to install. It is very flexible, easy to cut (knife) and easy to install with a staple gun.

I imagine (though an expert could better advise) the bats would give you better insulation than the foil.

Since we installed it, we have definitely felt the foil has helped quite a bit. I wouldn't call it cosy, but we no longer have the bitter cold we used to have, we use the heater less and we no longer need it on full blast.

Hope this helps,

Tim

Sally8

https://www.workshop.bunnings.com.au/discussion/comment/125707#Comment_125707

Thanks Tim! Regards Sally

Jason

https://www.workshop.bunnings.com.au/discussion/comment/125707#Comment_125707

Important note for our New Zealand readers:

The New Zealand Ministry of Business, Innovation and Employment (MBIE) issued a ban on the use of foil insulation in July 2016. The ban applies to the installation and/or repair of foil insulation in residential buildings. More information is available here: Foil insulation ban | Building Performance.

Thanks,

Jason

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