Fixing things to EPS EWI and render

[canalsiderenovation]

Likely to be our builders problem not ours for when he comes to fitting the downspouts back on but what sort of fixings should he be using to attach things like the downspouts and meter box cover (he has another over box thing here as the old one got damaged) and the extractor fan covers in the bathroom/utility (I known fans are better out of the roof but the rooms are have a flat roof and I didn't want it in the GRP roof).

 

Our rendered walls have 50mm of EPS and then the mesh stuff, base coat and silicone Ecorend render.

 

Also have things like outdoor wall lights to go up and obviously want to make sure they don't fall down either. 

 

And yes before anyone says that it would have made sense to put some ply etc or have prepared this before rendering I did mention it and asked these questions before hand but they know better ......

 

Edited July 12, 2021 by canalsiderenovation

[Adam2]

Up to 5kg per fixing with these ewi store

[canalsiderenovation]

1 minute ago, Adam2 said:

Up to 5kg per fixing with these ewi store

 

Perfect thank you.

 

Would you be so kind and let me know if there is something similar on Toolstation (I'm about to place an order). I saw these not sure if they are the same https://www.toolstation.com/dewalt-aerated-concrete-anchors/p80640?utm_source=googleshopping&utm_medium=feed&utm_campaign=googleshoppingfeed&mkwid=s_dm&pcrid=513183106262&pkw=&pmt=&gclid=Cj0KCQjw0K-HBhDDARIsAFJ6UGjYtIhFHvBBLhqOkF4gm7PzZaeKnYXH3Ksf4x7sdvbLfRQlbuE3qPIaAhWkEALw_wcB&gclsrc=aw.ds

[Adam2]

Not sure if they will work, maybe get some and test if you like on an offcut  but why not buy from EWI?

[canalsiderenovation]

35 minutes ago, Adam2 said:

Not sure if they will work, maybe get some and test if you like on an offcut  but why not buy from EWI?

 

The delivery cost from EWI is more than the cost of the item and I needed to make my Toolstation order up to £25. That said I'd rather get the right thing.

 

 

[Onoff]

@MarkyP might be your man for advice on this 

 

Think it's the norm to affix timber "strong points" to the wall pre mesh and render. The small area doesn't compromise the insulation too much. 

 

If not then you can get stand off plastic "tube" type fixings.

[canalsiderenovation]

4 minutes ago, Onoff said:

Think it's the norm to affix timber "strong points" to the wall pre mesh and render. The small area doesn't compromise the insulation too much. 

 

Too late! 

 

 

[tonyshouse]

If it is only 50mm thick then long screw into the masonry. QED

[Conor]

Use 120mm concrete screws for anything heavy or need to be secure, like sockets or handrails.

[Onoff]

18 minutes ago, Conor said:

Use 120mm concrete screws for anything heavy or need to be secure, like sockets or handrails.

 

Cold bridging surely? Or is it that it's minimal?

[Conor]

18 minutes ago, Onoff said:

 

Cold bridging surely? Or is it that it's minimal?

Minimal, unless you are using hundreds of them over a small area. 

[ADLIan]

The U-value should be corrected for the mechanical fixings securing the insulation & render system to the wall. A few extra fixings will have little, if any effect, but could be included in the correction if you want to be really critical

[MarkyP]

you can get some fat EPS plugs but I treid them and didnt get on very well with them, they made a bit of a mess of the render and pull out resistance wouldnt be very high. https://www.fastco.co.uk/fischer-fid-50-insulation-fixing-art-no-48213-pack-of-50.html?kw=pla-59448214701+c&fl=1000&ci=144812953870&network=pla&gclid=Cj0KCQjw6NmHBhD2ARIsAI3hrM1TU-dVJiD8hMpChoejXGQjU8m9s8xEtg47TpU_4l6u9GTLvhqfn78aAiEHEALw_wcB

 

my EWI is quite thick so came up with a way to avoid going all the way through, for things like lights I used long rawl plugs, drill a hole in render and EPS about 70mm deep, air spray to clear the hole, fill hole with squirty foam PU glue (mask face of wall first!), insert long rawl type plug watching for PU being splurged out, leave to set, then screw in with a relatively thin screw that only just bites the plug so as not to put too much rotational pressure on it. Worked well and the plug held without spinning and took a pretty strong fix but dont ask too much of the render.

 

otherwise fix right through to solid substrate, with a plastic rawl plug the thermal bridge won't be too bad, barely worth worrying about. watch for point loads on the render face and dont overtighten

 

 

[MarkyP]

I'm probably strating the obivous but use stainless screws otherwise you'll get a rust streak down your render face.