Removing and rebuilding hemp walls

During our absence from the building site for almost three weeks there was a severe storm and a large branch from a neighbour's gum tree fell onto the fence and into our yard. The fence was dented, but thankfully it missed the house - one of the reasons we deliberately did not locate the house under the gum trees. The storm also moved the hardwood pallets off the plastic they were holding down covering the pallets of binder. The pallet fell into the hemp wall but hardly damaged the wall, leaving only a 3mm deep line where it hit the wall.

Fallen tree branch and dented fence

The walls of the drier mixes we had done had been left to dry for three weeks, but were very soft and crumbly. Further inspection showed that the dryer mix had not solved the problems of the hemp wall pulling away from the timber frame around the doorways or the cracking. The dryer mix had both vertical and small horizontal cracks, however there was no cracking between rises, showing that wetting down a bit more between rises made a difference. The problem with the dryer mix was that it appeared that it had not bound together properly, when you ran a hand across it, in parts, the wall just crumbled away. The top of the window sill was also loose and crumbled when touched. This was in contrast to the wetter mix that had only been done the week before which was solid and did not crumble at all. Some parts of the dryer mix wall were more solid than others, but the mix where we had used 10 litres rather than 9 litres of water was more solid and much less crumbly than the 9 litre mix, although it was still weather than the wetter mixes we had done.

Video providing a comparison of the walls.

Horizontal crack mid rise in dryer mix

Vertical crack in dryer mix

Vertical crack in wetter mix

Marks showing where the wall has crumbled when rubbed

Worried that the render would not be sufficient to hold together the crumbly walls with out cracking we decided to demolish the walls we did with the dryer mix and redo them with a wetter mix. The ease with which the walls were able to be removed confirmed that we made the right decision to demolish them. It was also very obvious when we got the the walls that had been made with the wetter mix, they were hard and we could not easily remove them by hand.

Wall removal

Wall material taken out

 It had taken one day, 17 mixes, to do the dryer walls. It took half a day to remove the section and another day to rebuild them, and with the extra half a day we had we did the next rise in the main bathroom. This time we used an in between mix of one and a third buckets of water. Not as wet as our previous mix of one and a half buckets, but wetter that the too dry one bucket mix. This time we also made sure that we sufficiently wet down the joint between the rises. We used a child's watering can.

Kitchen wall redone

Wall solid even when form work just removed

New walls done too

 I followed Rodney Gregg's recommendation and got some washers used to attach Styrofoam and used these to put screws in to pull the wall back in where it had pulled away at the door edges. A large chain hardware store did not carry the washers, so I looked on the Internet for Styrofoam walling suppliers. Just when I thought I would have to drive a long way or get the  mail order. I found on the Internet that Culburra Beach Hardware was a distributor for Ezywall Styrofoam products, one of the accessories for which are the plastic washers I needed. So I purchased a box of 500 and have using them to pull the walls back to the studs where they have come away. It has worked a treat.

Ezy washer and screw

Hemp wall pulled in to stud

Wall pulled back in