Make my own dished chanels

[fryups]

Hi,

Am planning to dig around the perimeter of my house and install perimeter drainage with precast dished concrete channels. I will obviously be taking care not to go too low and am doing this as currently the external floor level is about 500mm above internal ground level and we have damp problems.

I have about 40 linear metres to do and prices I am finding are about £10 per m for precast sections. Therefore looking into to pouring them myself in molds. Has anyone tried this? Am trying to work out if it will be at all cheaper.

One section is approx 250mm *100mm*1000mm in volume, can anyone advise on the volume of concrete from one ready mix bag or will i be better off buying sand, cement, aggregate in bulk and mixing?

Any thoughts would be appriciated.

 

[john4703]

I made channels using a length of gutter in a wooden box, the gutter was upside down and screwed to the base of the box. I quickly realised that it was far easier to make sections of precast about 500mm long and set these with some 2 meters between them and cast the 2 metre length in situ. I set the short lengths of channel and used them as a form to screed the lengths between.
For corners and angles I took ages making a box and cutting plastic gutter exactly as needed and it worked well. I could not see any way of casting a corner in situ.

 

[fryups]

thanks, did you bed this just on a little mortar? Some advice says casting a concrete base to then bed the channel on which seems a little ott to me?

 

[john4703]

thanks, did you bed this just on a little mortar? Some advice says casting a concrete base to then bed the channel on which seems a little ott to me?

I just bedded them on a thick mortar bed. The ground underneath was well compacted. You do not want anything sinking after it is laid.

 

[jay679]

Would you not be better off fitting a french drain all round and running it off to a soakaway?

 

[fryups]

Hi,

My worry with a french drain right next to the house is the danger of drying out the ground too much and causing movement.

The house is a 16th C cob/rubble construction so foundations are likely to be little to non existent - one job i need to do asap is dig a trial pit and find out exactly what is going on with foundations.