insulate an enclosed veranda

[mlewin]

 

Hi, unfortunately I had termites in the enclosed veranda of my bungalow in Sydney and they ate all the old battens and lining boards.  I now want to insulate it before lining it back with Gyprock. This includes insulating the floor, which has dirt under it. I will be removing the floor as that has been damaged too and replace it with yellow tongue and carpet. What is the process for doing this for the walls and floor? Do I need a vapour barrier? 

[MitchellMc]

This is a fairly involved project @mlewin, and getting the insulation right before you line the veranda is really important for comfort and durability. For the walls, you’ll first need to rebuild the framing where the old battens and lining were removed. The stud framing needs to be deep enough to fit the insulation you plan to use. Typically, R2.5–R3.0 batts for external walls in Sydney. Once the studs are in place, you can place the insulation between them, then fix your plasterboard over the top. You’ll also need to think about how the top of the wall meets the windows or verandah framing. You can either install timber sills along the top of the studs or have the plasterboard carried up with rebates to create a neat finish.

For the floor, since the joists are close to the soil, a vapour barrier is strongly recommended. If you can access under the floor, you can install insulation batts between the joists and hold them in place with string lines or wire mesh. Once that’s in place, you’d lay a vapour barrier across the subfloor before installing your new yellow tongue boards. This helps prevent moisture from the soil affecting the insulation or floor finish. If access under the floor is limited, you may need to consider foam board insulation laid between the joists before fixing the flooring,

In summary, the key points are: proper stud depth for wall insulation, ensuring the insulation is held securely, and installing a vapour barrier under the floor to protect against moisture. Doing these steps carefully now will give you a warm, dry, and termite‑resistant veranda once it’s all lined and finished.

Please let me know if you have any questions.

Mitchell

[mlewin]

Thanks @MitchellMc. So have I got this right that the thermal layer is attached to the top of the joists directly over the insulation and then the yellow tongue flooring is directly on top? I have access to the area below the joists.

Since removing the floor today,  I have realised that a couple of the joists have been also eaten and they will need to be replaced. I also need to raise the floor level because previously there was yellow tongue flooring, floorboards then carpet. Can I just apply two levels of yellow tongue on top of each other to raise the height? 

I believe now that insulating the small amount of wall below the windows is going to encroach too much on already small room (1.9m x 3.5m) so I will concentrate on the floor and maybe just add some thermal curtains. Given this, will it be ok then to just batten out the room and directly add the gyprock? I will add the window sills on top of the battens.

[JacobZ]

Hi @mlewin,

Since you have access to the crawl space beneath the subfloor, the better option would be to install a vapour barrier directly against the dirt and then ensure that this subfloor cavity has adequate ventilation. Check out this discussion on How to add a subfloor ground moisture barrier for some guidance.

There are instructions for installing double-layered Yellowtongue on Page 5 of the STRUCTAflor Install Guide. Otherwise, you could just add 19mm strips of timber to the top of the joists to raise the height without the additional load or cost of using full sheets of Yellow tongue.  

You should be fine to battens out the walls instead of going with full frames. 

Allow me to tag @Nailbag, @Dave-1 and @R4addZ to see if they have any additional advice they can add to the discussion.

Let me know if you have any further questions.

Jacob

[mlewin]

Thanks. That black plastic is a cheaper solution. I will need to raise the floor by 28-30mm then add the 19mm yellowtongue. It will need to be timber that is at least H3 treated to go on top of the joists just to make it termite resistant. Any suggestions?

[R4addZ]

Hi @mlewin 

Whilst I can't comment on the timber side of things and not knowing the future use of the room, have you given thought to whether you need additional power, data or antenna connections in the room as now would be a good time to address that too.

If you are just going to batten the walls for the gyprok would it be worth using some spray foam as a thin insulation between battens. That said have you considered just glueing the gyprok to the walls?

[mlewin]

The veranda is off the main bedroom and was previously and will be again used as a walk in wardrobe/dressing room. It has always got notoriously cold in winter and boiling hot in summer (faces west). Condensation has been an issue too and I run a dehumidifier for most of winter removing a couple of litres of water every couple of days. 

I’m not sure why I haven’t considered glueing straight to bricks. Makes sense. Thanks!

[Nailbag]

Hi @mlewin 

I had an old 50's home that I was helping prepare with a builder mate of mine and from memory the scenario was very similar throughout most sections of the house.

We stapled builders plastic to the underside of the joists after replacing a few rotting ones and repairing salvageable ones. We ripped our own strips of timber to sit on the joists to compensate for an issue in one area that the floor finish wasn't going to match a different covering. Insulation batts were then laid within the joists resting on the plastic barrier. We are add additional sub-floor brick replacement vents for increased airflow.

When lining brick walls with plasterboard, unless the wall is way off and needs battens to straighten sections, then simply glue the sheets straight over. A few photos below show my last home I did this to.

Nailbag

[mlewin]

Wow! That looks great. I put a brick vent in today to try and increase some airflow. I was thinking that stripping down some timbers would probably be the cheapest and best solution. 2 layers of 22mm termite resistant yellow tongue is a bit pricey. Thanks for the tip on the black plastic and I am definitely going to just glue the plasterboard on. 

[mlewin]

After fully removing all the rubbish, I put strong plastic on the ground and only ran it up the brick footing a little bit. Should I have extended it further to cover the footing or will this suffice?