Nov 2015
Over the past couple of weeks I've been learning a few lessons.
a) Moving Koi from their home is a pain.
b) YouTube training videos make things look deceptively easy.
c) G4 sealant bonds very well to concrete, brick, mortar and skin.
d) I'm getting too old for this.
To set the scene.
We have a pond in the garden, full of koi. The picture gives you an idea of the pond ... it holds 4000 litres of water and a number of koi, each of which would easily serve a family of 8.
a) Moving Koi from their home is a pain.
b) YouTube training videos make things look deceptively easy.
c) G4 sealant bonds very well to concrete, brick, mortar and skin.
d) I'm getting too old for this.
To set the scene.
We have a pond in the garden, full of koi. The picture gives you an idea of the pond ... it holds 4000 litres of water and a number of koi, each of which would easily serve a family of 8.
The pond is a quarter circle of about 1.6meters radius and is 1.4 meters deep, with half of it below ground. It's a brick and concrete construction (base is concrete, walls are brick) with a lining of fibre glass. It's about 12 years old.
Correction .. it was 12 years old.
Correction .. it was 12 years old.
In August one of the slabs covering the top of the walls came loose and dropped into the pond. We thought nothing about this until we noticed the water level slowly dropping. We did a visual check of the bottom of the pond where the slab had hit (bit difficult to do with 1.4 m of water in the way plus some rather curious koi) and established that the slab had punctured the base in two places. Normally this wouldn't be a problem .. the fibre glass should be bonded to the concrete and as long as the concrete hadn't cracked there shouldn't be much of a leak .... but there was.
So, we had to drain the pond. This is not easy. For a start the occupants object to being left high and dry (or even low and dry). They react like .. well, like fish out of water. So they had to be found a temporary home. In the end we rented a show vat (basically a thick vinyl swimming pool) that could take the fish and about 1500 litres of their home. We also had to redirect the water going through the filters (for those who don't know, keeping koi is basically maintaining a sewage farm - they go to the toilet in the water and you have to process that water back into something fit to breathe - nice).
We managed to do all this, the fish were rehoused (reluctantly ... chasing a koi around a pond with a fishing net is not as easy as it sounds) and we were ready to drain the rest of the water from the pond.
Once the water was gone it became clear that the fibre glass was not bonded to the base .... or to the sides. The entire base had lifted, and the sides gave off a hollow noise when knocked. We then found a few more holes in the base and stepping on the base was like stepping on glass ... the base shattered.
We managed to find someone to repair the pond .. the sort of repair where the guy stands there, sucks his teeth and says "well I could do a bodge job but ...". In the end we went for the full repair .. that hollow sound in the walls worried me.
Sure enough, when it came to removing the fibre glass from the walls we found that the walls had been rendered in plaster, not concrete, and unlike concrete which is relatively waterproof, the plaster had turned to mud. We also confirmed that none of the fibre glass was bonded to the underlying base or walls and had pulled away, and that the lining itself was not fibre glass mat but a kind of spray on finish .. very VERY thin. Small wonder it had cracked when the slab hit it.
The discovery of plaster instead of concrete set us back. The walls had to be rendered in concrete, and we couldn't find a builder to do it quickly. With the fish in a tank a quarter of the size of their normal home and only running on half a sewage farm we couldn't wait three weeks for someone to come in and do it .. so I said I would do the rendering.
I know, I know .. but at the time it sounded sensible.
Now, my previous experience of wall rendering was .. well .. nil. Nevertheless, I watched a few YouTube videos and it looked really easy. So, I got my mortar mix (yeah, I chickened out .. I know it's 5 parts sand to 1 part cement but didn't want to buy in bulk) and started the job.
It wasn't as easy as it looked.
For a start, all the YouTube videos showed how to do it on a straight wall. The front wall of the pond was curved. Secondly they had had years of practice in smoothly applying the render. This compares to theyears months days experience that I had.
By the end of the day I had got the walls rendered. It didn't look quite like the videos. However, a bit of studying that night suggested that the first render wasn't usually smooth .. they allowed it to partially set and then cut it back and smoothed it off. I hadn't had that luxury .. the cold weather meant that the render took a long time to set.
The fibre glass guy came round and reckoned it was good enough to line ("Just don't try doing the walls of your house", he said), so he arranged to come round on the Monday.
They duly turned up and did the works .. bonding sealant on the walls, followed by two layers of fibre glass matt and a tissue layer all soaked in resin and finished off with a black resin coat. The only downside is that we turned the entire neighbourhood (and their cats) into glue sniffers
The final result looked great .. a bit lumpy (someone should have shot the renderer) but OK.
They left me to finish off the top .. reseat the slabs on the walls and this time make sure that they couldn't get knocked into the pond. Once again, I learned on the job ... my excuse is that the spirit level had been sniffing glue all day and its bubble was all over the place.
The final touch was to waterproof the mortar bedding the slabs so they didn't leach lime into the water. I used a product called G4 bond for this .. really good stuff. I carefully painted the mortar with it, trying to avoid drips. Unfortunately there were some, so I wiped them off with a sponge. This had the effect of spreading a thin film of G4 onto the fibre glass (and because I wasn't wearing any gloves .. a thin film onto my hands).
I can attest that firstly,'clear' G4 is more a milky white when it sets and secondly, it dries to a nice hard finish that bonds really well to the substrate .. in this case my palms and fingers.
It took two days before I could peel the bulk of it off.
Still, the fish are back home. They are not dead yet and fingers crossed, the pond isn't leaking.
Sure enough, when it came to removing the fibre glass from the walls we found that the walls had been rendered in plaster, not concrete, and unlike concrete which is relatively waterproof, the plaster had turned to mud. We also confirmed that none of the fibre glass was bonded to the underlying base or walls and had pulled away, and that the lining itself was not fibre glass mat but a kind of spray on finish .. very VERY thin. Small wonder it had cracked when the slab hit it.
The discovery of plaster instead of concrete set us back. The walls had to be rendered in concrete, and we couldn't find a builder to do it quickly. With the fish in a tank a quarter of the size of their normal home and only running on half a sewage farm we couldn't wait three weeks for someone to come in and do it .. so I said I would do the rendering.
I know, I know .. but at the time it sounded sensible.
Now, my previous experience of wall rendering was .. well .. nil. Nevertheless, I watched a few YouTube videos and it looked really easy. So, I got my mortar mix (yeah, I chickened out .. I know it's 5 parts sand to 1 part cement but didn't want to buy in bulk) and started the job.
It wasn't as easy as it looked.
For a start, all the YouTube videos showed how to do it on a straight wall. The front wall of the pond was curved. Secondly they had had years of practice in smoothly applying the render. This compares to the
The fibre glass guy came round and reckoned it was good enough to line ("Just don't try doing the walls of your house", he said), so he arranged to come round on the Monday.
They duly turned up and did the works .. bonding sealant on the walls, followed by two layers of fibre glass matt and a tissue layer all soaked in resin and finished off with a black resin coat. The only downside is that we turned the entire neighbourhood (and their cats) into glue sniffers
The final result looked great .. a bit lumpy (someone should have shot the renderer) but OK.
They left me to finish off the top .. reseat the slabs on the walls and this time make sure that they couldn't get knocked into the pond. Once again, I learned on the job ... my excuse is that the spirit level had been sniffing glue all day and its bubble was all over the place.
The final touch was to waterproof the mortar bedding the slabs so they didn't leach lime into the water. I used a product called G4 bond for this .. really good stuff. I carefully painted the mortar with it, trying to avoid drips. Unfortunately there were some, so I wiped them off with a sponge. This had the effect of spreading a thin film of G4 onto the fibre glass (and because I wasn't wearing any gloves .. a thin film onto my hands).
I can attest that firstly,'clear' G4 is more a milky white when it sets and secondly, it dries to a nice hard finish that bonds really well to the substrate .. in this case my palms and fingers.
It took two days before I could peel the bulk of it off.
Still, the fish are back home. They are not dead yet and fingers crossed, the pond isn't leaking.
