My daughter has just moved into a 150 year old cob cottage in Devon. She wants to attach curtain rails and shelves directly to the cob walls but is concerned that conventional plastic plugs and steel screws could cause damage.
Any recommendations about fixings for day-to-day needs like these? Are there specialist products avalable?

I think you would have to pilot drill, for that type of fixing on a solid wall. drill the same size as the inner dia of the fixing and all should be good.
tom

Thanks for these comments - our concern is that the expansion of the plug as the screw is driven home may cause cracking of the cob. I have read one article which suggests that a plastic insert is glued into a drilled hole to provide a housing which will hold the screw without exerting radial pressure on the cob. However the article did not specify any named products.

First posting on a forum
I've been renovating and living in an old cob cottage in wiltshire for the last 9 years. I took tuition from a lime plasterer for the care of cob walls. I believe the old technique (which I have used successfully) is to drill out a pilot hole and drive in a suitably sized wooden peg. For a reasonably secure fixing eg for a mirror or electrical socket I reckon it needs a square shaped peg about 5cm by 5 cm and about 20 long. The key is to knock in gently and if it seems to be holding and filling the hole snuggly carry on knocking it home. If you need anything bigger than a standard hammer your hole is too small! You can cut off any excess peg left sticking out when it's in far enough to hold firm. The cob will 'accommodate' the peg as it's driven in.
The other approach for really serious fixings (that I used to attach a wall beam) was bolts set in resin. Screwfix stock the type of product but I haven't used their brand: Fischer Hybrid Mortar Resin V 360
hope this helps