Concrete screws for cladding batons ?

[Nick Laslett]

I like these screws from Swiftfix. These are the same screws @Chanmenie used. 

https://www.swiftfix.co.uk/7-4-x-180mm-TX40-Blue-Power-Timber-to-Masonry-Screws-Box-of-100-p141442218

 

https://www.swiftfix.co.uk/7-4-x-200mm-TX40-Blue-Power-Timber-to-Masonry-Screws-Box-of-100-p141878417

 

Strong, have good corrosion resistant coating. I think these are the ones I used to fit the battens for my cladding, but would have to check. 
 

I alternated my fixings between the web and the concrete. Also did a few holes with the spiral fasteners. Rawlplug 80mm SPIRAL FIXING FOR EPS. 

 

https://shop.rawlplug.co.uk/facade-insulation-fixings/facade-insulation-accessories/iso-plug-plastic-screw-in-fixings/r-iso-plug-insulation-fixings/spiral-fixing-for-eps-80mm-box-of-40-r--iso--plug--80

 

So for example a 2 metre batten, with 400mm spacing would have 3 concrete screws, 3 in the web, or 3 spiral if not on a web point. Batten spacing would be 400mm, but for where boards joined, I would double batten. 

 

Edited October 4 by Nick Laslett

[Gus Potter]

On 03/10/2024 at 20:10, Firsttimer said:

We are using Izodom - 100mm EPS on the exterior, 25mm vertical batons, 25mm horizontal batons and 20mm cladding.

There will be a way of fixing this.. 9 times out of 10 at least.

 

What cladding do you want to fix? Is it timber or a cement based material or something else? It all starts with the weight of the cladding. Next is where are you in the country and what is the site altitude as we need to consider if there is any onerous wind loading that could peel the cladding away at the corners of the building say. I may sound a bit.. odd.. but all this info is essential to maintaining your cladding warranty and making the building perform say for 50 years.

 

To design the fixings I would start with the cladding weight and the wind load. From this I calculate the tension and bending force in the fixing. I then find a fixing that will do what I want it to do. Now from time to time depending on the timber strapping arrangement and how the cladding is mounted I may use heavier fixings at larger spacings to carry the weight of the cladding and other ones that take less work to install elsewhere and these are just designed to resist the wind loads.

 

I would fix into the concrete and not the web. The web is plastic and not suitable technically for this application. Aim for the large concrete area which is easy to hit. You need more fixings around say openings.. aiming for the web is not practicable. Also fixing into plastic has implications in terms of fire protection as the fixings heat up.

 

Post a sketch and some extra info if you can.

 

 

 

 

 

 

 

!

[Chanmenie]

Good post @Gus Potter I used Hardie VL Plank, they have installation instructions for weights and wind loads, which I used when designing my install 

[Firsttimer]

WE

On 05/10/2024 at 21:24, Gus Potter said:

There will be a way of fixing this.. 9 times out of 10 at least.

 

What cladding do you want to fix? Is it timber or a cement based material or something else? It all starts with the weight of the cladding. Next is where are you in the country and what is the site altitude as we need to consider if there is any onerous wind loading that could peel the cladding away at the corners of the building say. I may sound a bit.. odd.. but all this info is essential to maintaining your cladding warranty and making the building perform say for 50 years.

 

To design the fixings I would start with the cladding weight and the wind load. From this I calculate the tension and bending force in the fixing. I then find a fixing that will do what I want it to do. Now from time to time depending on the timber strapping arrangement and how the cladding is mounted I may use heavier fixings at larger spacings to carry the weight of the cladding and other ones that take less work to install elsewhere and these are just designed to resist the wind loads.

 

I would fix into the concrete and not the web. The web is plastic and not suitable technically for this application. Aim for the large concrete area which is easy to hit. You need more fixings around say openings.. aiming for the web is not practicable. Also fixing into plastic has implications in terms of fire protection as the fixings heat up.

 

Post a sketch and some extra info if you can.

 

 

 

 

 

 

 

!

We will be using Larch and going vertically. I believe the elevation of the site is about 165m. It's quite sheltered. 

 

Not got the time to do a sketch at the moment.

 

 

 

[Firsttimer]

On 04/10/2024 at 06:49, Conor said:

What a nightmare. I've looked at that systems photos and see what you mean. 

 

How are going to plasterboard the inside if you can't find webs easily?

You can see the webs from the interior.

[Chanmenie]

On 04/10/2024 at 06:49, Conor said:

 

 

How are going to plasterboard the inside if you can't find webs easily?

You can dot and dab onto EPS 

Plasterboard adhesive and Soudal Plasterboard adhesive foam both worked well on my EPS build

[Firsttimer]

@Nick Laslett @Chanmenie Hi both. What size batons did you use please ? The spec says a minimum of 30 * 50 mm , but I've already bought 25 *50 mm...

[Nick Laslett]

4 hours ago, Firsttimer said:

@Nick Laslett @Chanmenie Hi both. What size batons did you use please ? The spec says a minimum of 30 * 50 mm , but I've already bought 25 *50 mm...

I used a mix of 25x50mm and 25x30mm coloured roof battens. I followed the TDCA guidelines, but I was fitting thermowood timber. I actually bought the full book in the end, but I think the free one covers nearly everything. 
 

https://www.tdca.org.uk/publications/the-timber-cladding-handbook/

Edited November 4 by Nick Laslett

[Firsttimer]

21 minutes ago, Nick Laslett said:

I used a mix of 25x50mm and 25x30mm coloured roof battens. I followed the TDCA guidelines, but I was fitting thermowood timber. I actually bought the full book in the end, but I think the free one covers nearly everything. 
 

https://www.tdca.org.uk/publications/the-timber-cladding-handbook/

Thanks Nick. That's a great reference. Good to hear that you used 25mm deep, presumably without any issue. 

[SteamyTea]

On 03/10/2024 at 21:36, Gus Potter said:

So would I after say 3 months once the insulation has compressed / suffered from creep.. then you lose the friction that intialally makes it seem solid. Also if using timber battens the timber shrinks and that too further reduces the friction resistance.

 

After that you are relying on the bending capacity of the fixing alone..

Can you 'torque to yield' to overcome this problem.

Not sure if the yield needs to be the bolt (which is what is really being talked about here) or the insulation material that is taking the friction load.

Maybe some adhesive can come in handy.

[Chanmenie]

11 hours ago, Firsttimer said:

@Nick Laslett @Chanmenie Hi both. What size batons did you use please ? The spec says a minimum of 30 * 50 mm , but I've already bought 25 *50 mm...

I used 25 x 50, don’t think you can get 30 x 50  battens without having them specially made.

[Gus Potter]

On 04/11/2024 at 18:21, SteamyTea said:

Can you 'torque to yield' to overcome this problem.

Technically.. on paper maybe.. but you have such a mix of materials that it would just be a guess and probably too conservative.

 

The way to design it is to assume the fixing is acting like a short cantilever out from the wall.. like a dowel supporting say a flying shelf in you kitchen. You then add the wind load sucking the cladding off the wall which adds tension to the fixing.

[SteamyTea]

10 minutes ago, Gus Potter said:

Technically.. on paper maybe.. but you have such a mix of materials that it would just be a guess and probably too conservative.

Rubber washers, they can compress easily, spread load of a larger area and are very compliant if made from the correct compound.

[Gus Potter]

26 minutes ago, SteamyTea said:

Rubber washers

Just for you @steamy! Below is a knocked up (it's not prefect but hopefully gives you the jist) idealised model of some of the forces in the fixings. In real life they behave in a much more complex manner. Maths wise its pretty easy to solve this, quadratic equation or if lazy just use the goal seek function in excel. Now intially I would apply a lot of safety factors.. mostly to do with the local crushing of the masonry at the outside edge.. then wind them back by saying.. if I use a few more I can handle a few failures.. which is basically what a lot of builders do.. chuck in a few more if in doubt.

 

On 04/10/2024 at 22:18, Nick Laslett said:

I like these screws from Swiftfix.

For all the easy way if you are buying a lot of fixings is to contact say Hilti / Fischer et al and ask for advice. They may (and often do)  send out a rep.. to do a few load tests on site.. On something that is a bit out the norm I would take a fag packet approach (idealised model) as above so I don't end up with too much egg on my face = being wildly wrong and also as a second qualitative check in case the rep gets it wrong.. which is sensible.

 

[Nick Laslett]

@Gus Potter, thank you for the model.  If it is of interest here are some specifics from the data sheet for the Eurotec screws. 
 

https://app.nextpim.de/Cloud/6118eacef55a4834b44c3623/a3ba70a2-990d-432c-fb8c-08d79e6bb09c/Product_data_sheet_Blue-Power_Systemschraube_EN_06_2023.pdf

 

For fastening timber substructures to concrete. When the system is installed on façade insulation, the insulation absorbs a proportion of the transverse forces. The insulation product must therefore have a compressive strength of at least 50 kPa at 10% compression.

Static Values

For fixing in Concrete C20/25

Tensile load bearing capacity = 2.5kN

Shearing load bearing capacity = 0.75kN

 

The manual from the ICF supplier doesn’t really go into any great details about fixing external timber battens. The two biggest challenges were finding a concrete screw long enough to go through a 25mm batten and 100mm EPS, + 50mm minimum fixing depth, and the need for some kind of external weather rating. The Eurotec screws are rated for C4 environments and appear to be designed for going through 100mm+ of insulation, then affixing into concrete. One of the things I liked about the Thermohouse ICF blocks was the specification of the EPS, they have a compressive strength of 150 kN/m2 at 10% compression, EPS density of 24kg/m3. 

Edited November 7 by Nick Laslett

[Gus Potter]

54 minutes ago, Nick Laslett said:

The manual from the ICF supplier doesn’t really go into any great details about fixing external timber battens. The two biggest challenges were finding a concrete screw long enough to go through a 25mm batten and 100mm EPS, + 50mm minimum fixing depth, and the need for some kind of external weather rating. The Eurotec screws are rated for C4 environments and appear to be designed for going through 100mm+ of insulation, then affixing into concrete. One of the things I liked about the Thermohouse ICF blocks was the specification of the EPS, they have a compressive strength of 150 kN/m2 at 10% compression, EPS density of 24kg/m3

Nick (fixings) they won't commit to. This is not part of their design liability. This is completely understandable, they are just giving a representative example.

 

Fixings are rated in two not least general ways. One is the exposure rating.. your C4 wet dry.. near the sea (salt air for example) the other is strength. The ICF folk can't be expected to recommend fixings for all the different combinations of insulation and wall cladding.

 

For all. Most structural fixings these days are based on the Eurocode design and have what is call a European Technical Approval (ETC). Hilti et al have a link on their web site to which states how their fixings are tested and in what environment they are appropriate for. These are hard reading and difficult to navigate if you are not familiar with the terms and notation.

 

Your easy way around this is to treat the fixings like a dowel supporting a flying shelf. The compressive strength of the insulation can be neglected for the most part. The higher the compressive strength of your insulation the lower the thermal resistance.. think of insulation like cells in the body.. the cell walls are more conductive. A higher strength insulation needs more and smaller cell walls.

 

Now maybe you don't need millions of fixings? .. which technically could introduce repeating thermal bridges. Can you design the cladding like a curtain wall / rain screen panel where the panels are supported at the bottom ( carries the weight) and the top fixings just stop it pealing off in the wind?

 

Maybe look at this in a different way?