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How to replace exterior wall wood panels?

Andrew14

Hey Team,

I have a timber extension that was built with thin wood panelling as walls (non-bearing, simply filling the gaps in the timber frame). Some of the panels are starting to get damaged due to exposure to the rain. I'd like to replace them, and take the opportunity to do a better job than the original build (if I can manage!).

The panels are probably 6 or 7 mm thick, so thin that some tapping on a sodden area produced a hole (taped over as you can see in the pics - black tape inside; silver tape outside).

The frame around them seems solid enough, albeit there's a small leak somewhere: I can see water slowly dripping inside on very rainy days. I also had to patch some rotten wood on the outer timber frame (black spot in the exterior photo, at the bottom of the timber frame - that's bitumen).

Question 1: if I where to simply replace the panels, keeping the same design, what could I use? I'm definitely open to some texture or even a stacked washboards look rather than the fairly plain panels I have.

Question 2: if I wanted to upgrade the setup, would it make sense to stick some insulation in, sandwiched between an exterior and an interior panel? The frame is relatively thick.

Thanks in advance!

Andrew

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EricL

Hello @Andrew14

Before you begin, I propose having your walls tested for asbestos for health and safety. If the test is positive, you'll need the services of an asbestos removal specialist. If the test is negative, you can continue with your repairs.

Thank you for sharing your question about your exterior wall panels. I propose using either https://www.bunnings.com.au/1217-x-607mm-x-12mm-plywood-hardwood-marine-aa-grade_p0320031 (on the condition that it is big enough) or https://www.bunnings.com.au/2440-x-1220mm-12mm-plywood-hardwood-marine-aa-grade-12mm_p0320024 if it needs to be bigger. It is well-suited for outdoor use because it features waterproof A-bond glue and high-quality defect-free veneers, but you must properly seal all the edges and faces before exposure to weather. The same goes for the timber moulding you'll be using outside.

If you are thinking of using https://www.bunnings.com.au/james-hardie-4200-x-180-x-16mm-linea-weatherboard_p0710203 or https://www.bunnings.com.au/james-hardie-4200-x-230-x-7-5mm-fc-woodgrain-hardiplank-weatherboard_p0716249 . It is possible to use these boards; however, they will stand out and be totally different to the design you currently have on your wall.

However, before you begin taking things apart, I propose tracking down the source of the leak and fixing the issue first. In this manner you won't get any water travelling down and gathering in that spot of your wall. In regard to the insulation, on the condition that there is enough space for batts, it is always a plus when you have insulation in your wall.

Let me call on our experienced members @Nailbag, @DIY4Knuckleheds, @diy_hausdesigns and @Dave-1 for their recommendations.

If you have any other questions we can help with, please let us know.

Eric

Dave-1

Good Evening @Andrew14

I like the marine ply that @EricL has suggested, it stays true to your original design and also will be more heat tolerant to transferring the sun from outside to inside.

The water leak tho and where its rotted is what I would be looking at first. If your remove the tar and see how far the rot (if any) has spread and then use Earls Wood hardener if the timber isnt in too bad a condition.

@EricL has a good point in checking for asbestos as the era the panels were installed might have been used.

Dave

Andrew14

Thanks @EricL and @Dave-1! I'll start with some flood tests and see if I can figure out the leak. The extension is relatively new and I'm confident there won't be asbestos, but thanks for flagging.

For insulation batts, any recommendations?

And should I layer any plastic sheet in between the wooden panels?

Thanks

EricL

Hello @Andrew14

I suggest measuring the gap between the panels first so that you can determine which insulation will fit. If you are only filling in a small portion, I suggest looking at the https://www.bunnings.com.au/earthwool-r2-5hd-multi-use-roll-90mm-x-430mm-x-8500mm-3-7m-1-pack_p0524197 . I recommend looking at the https://www.bunnings.com.au/ametalin-1350mm-x-10m-silverwrap-ld-reflective-wall-insulation_p0811067 to cover the timber frame.

Here is a link to the Ametalin brochure: Ametalin Brochure

If you have any other questions we can help with, please let us know.

Eric

Andrew14

Thanks @EricL , appreciate it.

Dave-1

Good Evening @Andrew14

Do you know what the timber panels are made of? As @EricL has mentioned measuring the width of the studs will give an indication. But I am thinking of the two different types of paneling material might slow down the ehat transfer.

Dave

Andrew14

@Dave-1 they are about 850W x 700H. From the water-damaged part I can see that they look like plywood.

I also found (at least one) source of the leak. From flood tests, it seems to come from gaps in the timber frame at the bottom corners of the window. See photos. The water then makes its way inside the frame and into the house. See interior photos (cornice removed). I was thinking of selling the gaps with silicone and waterproof tape, and also add draft excluders on the side of the windows (that's where the flood tests showed the water was getting into the sides and down to the bottom corners, where the gaps are). Would that be good enough?

Thanks!

JacobZ

Hi @Andrew14,

Silicone sealant and waterproofing tape can be effective at preventing water from entering when they are applied in the correct location. It certainly can’t hurt to seal off that area, but there is no guarantee it is the sole cause of the leak, as water can enter higher up and travel along the framing before becoming visible.

Once the area has been sealed, test it with a controlled hose test, working from the bottom upwards, to confirm whether the repair has been effective.

If you find other entry points, let us know and we can look at how best to address them.

Jacob

Dave-1

Good Afternoon @Andrew14

I am always hesitant on waterproof tape. Mainly because I dont trust it will stand up to the test of time.

Some of those stud ends look like that may have a bit of rot in them? Can you push a flat head screwdriver into them? If you can then that needs to be looked at first.

I would keep in mind that the water will find the easiest path when you silicone. It kind of looks like the water entry is coming from further up if you look at the damp pattern?

Dave

Andrew14

@Dave-1 yes the whole frame and wall should be knocked down and rebuilt I reckon, but that's a huge job. I'm trying to patch up what I can until I can plan a potential renovation in the future.

There is indeed some rot at the end of the studs. I'll need to fill those gaps at least to continue flood testing further up the wall, so it's more of a diagnostic fix.

Dave-1

Afternoon @Andrew14

Sometimes jobs can feel immense. We all reach a point (I did with my storm water) but breaking it down as you are into doable sections works extremely well.

I have seen this product showcased in Facebook land (check out their Facebook page and also have a look at their putty)

Earl's 250ml Wood Hardener It really looks and sounds like it works for non intense rot.

Id be tempted to start up top and work my way down in searching for the leak, once found have a look at the other windows/panels as they were probably all installed the same way.

Its hard to be positive when something is hard to figure out, but the joy when you do :) Worth working towards for sure.

Dave

Andrew14

Thanks @Dave-1 ! Appreciate the positive boost. It can get overwhelming. I'll take a look at the hardener and keep up my leak investigation.

Andrew14

Update: I've ripped out most of the window casing to expose the frame (first picture).

I've done extensive flood tests by covering the window in plastic sheets to see if any water was leaking from above the frame and down the sides, to pool at the bottom of the frame. Nothing. I could only reproduce the leak by flooding the front-bottom of the window (when the casing was still on). So it doesn't look like a leak internal to the wall, but more localised to the bottom of the window.

My best guess is that water is getting in from both the sill corners and also leaking behind the bottom casing board from the sides. Water pools in 2 main areas (arrows in red in the second picture):

Window sill;
Gap in the timber under the bottom casing board.

Assuming that's correct, my plan is:

Use the wood hardener on all water-damaged timber;
Fill any holes in the timber with putty (e.g. circled in the second picture);
Cover the window frame with a bitumen membrane;
Re-fit the casing boards with more bitumen on the joints;
Re-paint everything.

Is that good?

Should I add any flashing?

Any gap that I should specifically NOT fill cause it serves a purpose (like the weep holes at the bottom of the window frame)?

Thanks!

EricL

Hello @Andrew14

That sounds like a good plan. I would avoid filling in the weepholes and any other channels that serve as a drain point for rainwater. I suggest using https://www.bunnings.com.au/selleys-430g-white-no-more-gaps-exterior-gap-filler_p1230161 where it's appropriate as bitumen surfaces can't be painted.

If you need further assistance, please let us know.

Eric

Andrew14

Thanks @EricL , what I wanted to do was to seal the unexposed timber before replacing the boards. I mentioned bitumen cause I have a can lying around, but perhaps it's not the best product? I could use the sealant I'll get for the marine plywood, or simply use primer + exterior paint? Essentially I want some redundancy Iayers protecting the underlying timber, as clearly the window is not greatly designed.

Cheers,

Andrew

Dave-1

Morning @Andrew14

A note of caution with bitumen paint. Its not really easy to paint, use glue or anything over it. Its great at waterproofing but dosnt look great if left on the surface.

Dave

MitchellMc

Hi @Andrew14,

Any quality exterior paint, such as Dulux Weathershield, provides a water-impervious layer. So, you can just use your exterior paint to coat the internal timber, for that extra layer of protection.

Mitchell

Andrew14

@Dave-1 I was looking at this Bondall sealant as an alternative (which I'd use on the marine plywood panels anyway), then add primer and paint on top. Thougths?

Dave-1

Good morning @Andrew14

I have not used that one so "hands up in a shrug" type deal :) Tho I think @MitchellMc was typing an answer at the same time as your question that will negate the sealant question. :)

Dave

MitchellMc

The sealant is certainly an option @Andrew14 and would add a second layer of defence. Ultimately, though, preventing water from entering the cavity in the first place is the priority.

Mitchell

Andrew14

A very good point @MitchellMc. I noticed that the trimming boards around the exterior side of the cavity are on the narrow side, not quite covering the frame on the sides, and exposing a large, unsealed cavity at the bottom (one of the entry points for the leak, actually).

Should I install a wider trim? Or add other guards under the original trim?

Thanks

JacobZ

Hi @Andrew14,

I'd definitely replace the architraves if they are leaving that seam exposed. You could simply seal them with silicone, but if you add a wider trim, then seal the seam between that trim and the wall, it is much harder for moisture to track around the corner and into the seam in your photo above.

How wide are the trims that are there now? How many mm off the seam are they?

I can certainly recommend something if you'd like.

Let me know what you think.

Jacob

Andrew14

Hey @JacobZ ! The side architraves are 60mm wide, but the whole seam, including the width of the boards, is 66mm.

At the bottom, the architrave is 100mm wide but to cover the gap fully I'd need at least 130mm. I'm constrained by the thickness of the architraves (about 12mm), as the top one needs to fit under the existing flashing. Any suggestions? Cheers

EricL

Hello @Andrew14

I could only find the https://www.bunnings.com.au/66-x-18mm-5-4m-moulding-h3-treated-pine-fj-primed-half-splayed-2-losp_p8423194 which I believe is too thick. There is one at https://www.bunnings.com.au/138-x-30mm-5-4m-f7-h3-treated-pine-primed-losp_p0053194 , again it is quite thick and not close to the 12mm you are after. The only other option that comes to mind is to change the flashing so that the thicker trims will fit.

Eric

Andrew14

Thanks @EricL really appreciate the search. I'll have a look.