How to re-attach box gutter to rendered wall?

The box gutter has detached itself from the rendered wall. I tried a similar screw which was a little larger than the original but it didn't hold. It seems impossible to find the stud behind the render so I'll need to drill into render and blueboard(?). Are there special screws that will work in this instance, is there another way to attach this gutter?

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JacobZ

Hi @tigerzen,

I reckon it's fairly likely that they have just screwed the end of the gutter to the render or blueboard, and that there is no actual stud behind that location. If you've tried a longer and larger screw without any effect, then this helps to confirm my suspicion.

My suggestion is to apply a bead of silicone to the back of the gutter, then use Ramset M4 x 8mm Hollow Wall Anchors to fix the gutter back in place.

You'll have to use a masonry bit to create a pilot hole for this anchor. If, while drilling your pilot hole, you hit something solid, like timber, we can always adjust the approach and install a Green Wall Plug, then screw it in place with the same screws that were used previously.

Let me know what you think and if you have further questions, please don't hesitate to ask.

Jacob

tigerzen

https://www.workshop.bunnings.com.au/discussion/comment/57513#Comment_57513

Hi Jacob,

Thanks for the quick reply. There's no stud that I can feel, the drill easily drills through the render, looks like it will be Ramset anchors. The anchors your link refers to states plasterboard, I assume that they will be fine for outside use as well? Also, just a general question, on a rendered surface, how does one find where the studs are, internally I'd use a stud finder, look for nail holes etc., what do you do with a rendered surface?

JacobZ

https://www.workshop.bunnings.com.au/discussion/comment/91096#Comment_91096

Hi @tigerzen,

Hollow wall anchors will work the same in fibre cement and plasterboard as long as the wall material is around the same thickness.

It's not an ideal solution because hollow wall anchors aren't galvanised, so it will be a weak point in terms of rust, but in this situation, unless you could get access behind the rendered wall to install some timber, it's about the best you can do.

If you sprayed the anchor with a protective coating like this Dulux Metalshield Zinc Galv Spraypak before installation, then dab some silicone over the screw to protect it from moisture, this should help to protect against rust, but there is still a chance.

In saying this, it looks like the original screw they used was gold passivated, so it would be much the same as what was already there.

Finding a stud would be much the same as indoors. A scanning type studfinder, if calibrated correctly, should be able to pick up studs in the same way. Personally, I prefer using a magnetic stud finder like this Trojan Magnetic Stud Finder to locate the screws or nails used to secure the sheets in place. Screws and nails mean there are studs behind the sheet.

Let me know what you think.

Jacob

tigerzen

https://www.workshop.bunnings.com.au/discussion/comment/111506#Comment_111506

Thanks again Jacob, I've got at least a couple of studfinders, I didn't know they could work through render.

JacobZ

https://www.workshop.bunnings.com.au/discussion/comment/123192#Comment_123192

Hi @tigerzen,

It really depends on the quality of the studfinder. They might be effective, they might not, but higher-end models tend to perform better with things other than plasterboard.

They work by picking up changes in density. Some studfinders might struggle because the render is denser than the plasterboard that they are marketed for and are typically used on.

That's why I prefer the magnet style of studfinder. As long as there is a screw or nail within about 30mm, they will react to it regardless of the density of the material in front of it.

I'd just give your studfinder a try and see how it goes. If you can't pick anything up, try a magnet style studfinder.

Let me know what you think.

Jacob

tigerzen

https://www.workshop.bunnings.com.au/discussion/comment/130856#Comment_130856

Just another question, I've noticed that the downpipes have all been installed with self-tapping screws as well and have come loose a little. Again they're installed into the rendered surfaces. Are there any other options beside the anchors, it seems there could be a few to replace?

JacobZ

https://www.workshop.bunnings.com.au/discussion/comment/135571#Comment_135571

Hi @tigerzen,

Unless there is something behind the wall that can be screwed to, then the anchors are likely your best option.

The only other thing I could think to do is spray some expanding foam through a pilot hole in the render, insert a Wall Plug while it is still wet, allow it to dry, then screw into the wall plug.

These aren't perfect solutions, but they should hold better than simply screwing into the render.

Allow me to tag @Nailbag, @R4addZ and @Noyade to see if they have any ideas.

Jacob

tigerzen

https://www.workshop.bunnings.com.au/discussion/comment/138764#Comment_138764

Thanks again Jacob, some interesting ideas and thanks for reaching out to the others.

R4addZ

https://www.workshop.bunnings.com.au/discussion/comment/140890#Comment_140890

Hi @tigerzen

You can get Nylon cavity fixings and coupled with a Galvanised or good quality stainless steel screw you shouldn't need to worry about corrosion. The weight limit of the ones in the link below is 10 Kg so you may need to add more depending on expected load over the length of the gutter, they should be ok for the downpipes as the water doesn't particularly add much weight to the load as it is simply falling down the pipe.

https://www.bunnings.com.au/ramset-8-x-12mm-ramtoggle-4-pack_p2260486

As a guide, a litre of water weighs a Kilo so say over the length of 1 metre you expect a maximum of 10 litres in the largest down pour (I can't say these are real figures as I don't know the capacity of your gutters) each metre should have at least 3 fixings (you have to allow for the weight of the actual gutter). And don't forget to silicone over the screw heads to ensure no water can seep through or better still use rubber washers.

Noyade

https://www.workshop.bunnings.com.au/discussion/comment/140890#Comment_140890

Afternoon @tigerzen

I'm not expecting you to own an orthopaedic screw depth gauge, seen below, but you can replicate something similar with a length of wire and a sharp small bend at the end.

Remove the Tek screw seen in your photo.

Start probing.

See if you can find 'wood' inside. Anything that could accommodate a screw and also noting the direction and length required.

If just an empty cavity - rest the bent end on the inner surface of the wall - mark the wire.

Depending on the length - I'd then start looking at hollow wall anchor hardware.

If any of that makes sense.

Cheers.

R4addZ

https://www.workshop.bunnings.com.au/discussion/comment/142470#Comment_142470

Hi again @tigerzen

I decided to go looking for something that could take more weight. Again I would replace the supplied screws with galvanised or stainless but with these, according to the weight they supposedly can take, I would expect the blueboard to give way before the fixings. Bunnings special order team may be able to get them in for you.

https://shakespearesolutions.com.au/products-page/wall-fixings/geefix-cavity-wall-fixings/?srsltid=AfmBOoqJRidPulwWlQTbihcCExlFxPG9UUq7WpVSBlLOxjcubeISBmSt

A bit more work to fit but a massive increase in weight handling!

Nailbag

https://www.workshop.bunnings.com.au/discussion/comment/135571#Comment_135571

Hi @tigerzen

A stud finder definitely wont work through render unfortunately. And I suspect its possible that behind the render is actually foam board not anything solid such fibre cement blue board. The original screws have given way because they were only screwed carefully just into the render itself being less than 100mm thick.

You can test this by making a small 4mm hole just through the render itself. Then see if you can push through an open ended coat hanger wire, If you can then its foam board, which traditional fasteners wont be effective.

You might need to fix a metal plate to the back of the header (box gutter) with screws or rivets. Then apply a Sika-flex adhesive to the back of the plate and then put a prop hard up against the head over night to all the adhesive to dry.

Nailbag

Screenshot 2025-09-28 at 6.24.05 pm.png

tigerzen

Thanks Noyade and R4addZ for your thoughts, I appreciate your input. I did probe around the holes and I didn't detect anything solid. Looks like it will have to be some sort of cavity fittings, from what I can tell every fixing has used these self-tappers so could be a few to replace but I'll wait until they're a problem before I change them, atm it's just the box gutter.

tigerzen

https://www.workshop.bunnings.com.au/discussion/comment/138767#Comment_138767

Nailbag, you're right, it's foamboard, not fibre-cement making it worse than what I thought. I contacted a plumber today who wasn't sure what attaching method to use, he said he'd need to research it further.

EricL

https://www.workshop.bunnings.com.au/discussion/comment/140894#Comment_140894

Hello @tigerzen

I propose following @Nailbag's suggestion as there are no studs or solid fixings behind the foam board.

Eric

tigerzen

Thought I'd give an update on this. We engaged a plumber who promptly gave us the bill and said it was fixed. I went up to have a look and it's in exactly the same shape it was before ie not connected and with some silicon patches which were used to try and attach the gutter to the rendered wall. Now it's worse as there are repeated attempts at screwing fasteners into the rendered wall which have now left some bigger holes in the wall. I have no idea how to plug these holes (builder's bog perhaps?). I have since discovered that the exterior walls are polystyrene panels with a few layers of render so not sure how to fill the gaps. Back to square one, finding a prop to hold the gutter to the wall seems difficult as it's high up off the ground.

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/58474#Comment_58474

Hi @tigerzen,

I'd be inclined to fill all the holes with exterior silicone to prevent water ingress, or you could use mortar and paint over it.

For the fixings, as Jacob mentioned, I'd go for an expanding toggle. However, if they are long enough for the thickness of your sheets, go with Ramset 3/16" x 100mm Round Head Spring Toggles as the wings will capture the back of the sheets. However, if you have 100mm thick sheets, these likely would be long enough. The other option is to potentially try Wallmates. When fixing lightweight objects to foam board, a similar style of screwed fixing is used.

Mitchell

tigerzen

https://www.workshop.bunnings.com.au/discussion/comment/91603#Comment_91603

Thanks Mitchell for the advice. After poking around in the polystyrene walls it feels quite thick, do you think the toggle bolt would still work? Also I thought Builder's bog would be a better filler as it can be screwed into therefore creating a place to hang the gutter to.

EricL

https://www.workshop.bunnings.com.au/discussion/comment/111802#Comment_111802

Hello @tigerzen

Are you referring to the Ramset Super Wallmate Toggle Anchor? Did you have another toggle in mind? If it is the Super Wallmate, it's important that there is enough space for the toggle itself to swing loose in order to operate properly.

If you need further assistance, please let us know.

Eric

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/111802#Comment_111802

You could use Builder's Bog if you need to drill into those sections again @tigerzen. The only way to know if a Ramset 3/16" x 100mm Round Head Spring Toggles will be long enough is to try it or measure the thickness of the cladding somehow.

Mitchell

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