Suitable clay lump fixings.

[Bogart]

What do people use to secure items to clay lump? Ineed to affix a few outside wall lights, not heavy, and am considering using decent wall plugs unless others have better ideas.

 

[Feltwell]

Never had a house made from the stuff, how solid is it? Rather than plugs, which put an expansive force into the clay, it might be worth trying masonry screws - these are designed to cut in with no plugs, so they don't put much of an expansive force inside the material. They're also much longer than normal plugs, more chance of getting a decent purchase maybe?

https://www.screwfix.com/c/screws-nails-fixings/masonry-screws/cat840054

The other non-expansive one would be resin fixings, but that sounds very OTT for a wall light!

 

[philpjuk100]

lengths of threaded rod (4 or 5mm) through the wall with a plate on the inside? then hang a picture or plate over it, or fasten the light switch to it? only a suggestion never owned a "mud hut".

 

[Bogart]

Never had a house made from the stuff, how solid is it? Rather than plugs, which put an expansive force into the clay, it might be worth trying masonry screws - these are designed to cut in with no plugs, so they don't put much of an expansive force inside the material. They're also much longer than normal plugs, more chance of getting a decent purchase maybe?

https://www.screwfix.com/c/screws-nails-fixings/masonry-screws/cat840054

The other non-expansive one would be resin fixings, but that sounds very OTT for a wall light!

I did think of the resin ones but like you thought a bit over the top for a light fitting weighing next to nothing. Am not sure the screws you suggested wiuld work as the clay lump is shall we say not the a very dense material and such screws assume that having small minor diameters.

 

[Bogart]

lengths of threaded rod (4 or 5mm) through the wall with a plate on the inside? then hang a picture or plate over it, or fasten the light switch to it? only a suggestion never owned a "mud hut".

Added expense of purchasing pictures.

 

[Flyfisher]

I did think of the resin ones but like you thought a bit over the top for a light fitting weighing next to nothing.

Part of our house is built with chalk block, which I'm guessing is harder than clay lump but is still fairly soft and I've found that when fixing an outside light it's best to use a fairly long fixing to spread the load, something like 3-4 inches, compared to a 1-2 inch fixing that would be perfectly adequate in a brick wall. The other problem is that any form of expansion fixing (e.g. rawlbolts or even wall plugs) risks fracturing the soft material near the surface. This is less of a structural problem if long fixings are used, though it might be a decorative problem depending on the design of the light fitting. One method to avoid this is to only plug the bottom two inches or so, ie drill a 3-4 inch hole suitable for the plug then drill a slightly larger diameter hole to a depth of two inches. Insert and push the plug to the bottom of the hole and use a 3-4 inch screw to make the fixing. The bottom two inches of the screw should hold firm and being deeper within the wall means less chance of breaking off any material near the surface, where there should be almost no pressure from the fixing.

For a more substantial fixing, I've used resin-fixed stainless coach bolts to fix a piece of oak to the wall and then fixed the lamp to the oak. Resin fixings might sound a bit OTT but they are effective at spreading loads within the wall with little risk of damage to the wall material. I've used this stuff, which is cheap enough and doesn't require a special application tool unlike some of the more 'professional' resins: https://www.screwfix.com/p/easyfix-kem-psc-175-ef-chemical-resin-175ml/5650J

 

[philpjuk100]

If you "chase" the wall for cables what do you fill it with? mud?

 

[Me!]

I've not tried this in clay lump, but we have some wattle and daub where the daub seems to be mainly clay, where it works well.
Drill a longer hole than you would use for a normal wall plug, about 3" or 4" and which is just a bit smaller than the outside diameter of the screw. Then fill the hole with a good squirt of water-based no-nails type of adhesive and gently insert the screw whilst the glue is still wet. The no-nails seems to soak in to the daub enough to stop it crumbling and to give a surprisingly good fixing.

 

[Bogart]

I did think of the resin ones but like you thought a bit over the top for a light fitting weighing next to nothing.

Part of our house is built with chalk block, which I'm guessing is harder than clay lump but is still fairly soft and I've found that when fixing an outside light it's best to use a fairly long fixing to spread the load, something like 3-4 inches, compared to a 1-2 inch fixing that would be perfectly adequate in a brick wall. The other problem is that any form of expansion fixing (e.g. rawlbolts or even wall plugs) risks fracturing the soft material near the surface. This is less of a structural problem if long fixings are used, though it might be a decorative problem depending on the design of the light fitting. One method to avoid this is to only plug the bottom two inches or so, ie drill a 3-4 inch hole suitable for the plug then drill a slightly larger diameter hole to a depth of two inches. Insert and push the plug to the bottom of the hole and use a 3-4 inch screw to make the fixing. The bottom two inches of the screw should hold firm and being deeper within the wall means less chance of breaking off any material near the surface, where there should be almost no pressure from the fixing.

For a more substantial fixing, I've used resin-fixed stainless coach bolts to fix a piece of oak to the wall and then fixed the lamp to the oak. Resin fixings might sound a bit OTT but they are effective at spreading loads within the wall with little risk of damage to the wall material. I've used this stuff, which is cheap enough and doesn't require a special application tool unlike some of the more 'professional' resins: https://www.screwfix.com/p/easyfix-kem-psc-175-ef-chemical-resin-175ml/5650J

Yes think will give this a go as it seems a fairly cheap method of fixing with no expansive forces.

 

[Bogart]

I've not tried this in clay lump, but we have some wattle and daub where the daub seems to be mainly clay, where it works well.
Drill a longer hole than you would use for a normal wall plug, about 3" or 4" and which is just a bit smaller than the outside diameter of the screw. Then fill the hole with a good squirt of water-based no-nails type of adhesive and gently insert the screw whilst the glue is still wet. The no-nails seems to soak in to the daub enough to stop it crumbling and to give a surprisingly good fixing.

As I have got 6 of these lights to affix to the outside of various clay lump outbuildings so will get the resin and also try your suggestion of no nails type stuff as well.

 

[Bogart]

If you "chase" the wall for cables what do you fill it with? mud?

As they will be fitted to outbuildings the inside look is not paramount so will use mini trunking, if self adhesive does not work which it might struggle to do , will dab it with the no nails stuff.