A few questions

[mattrgee]

Everyone here seems to know their stuff, hope you can answer the following few questions

1. I will be laying a sub base of MOT1 with a final compacted depth of 75mm. By how much will MOT1 compact by? i.e. do I need a depth of 100mm to achieve my final compaction depth of 75mm?

2. Can I lay the MOT1 in well advance of the bedding layer and flags? With the weather being so bad I was going to lay the sub base one weekend and then the bedding layer and flags on the next available weekend. Will the sub base come to any harm exposed to the elements?

3. Should I leave the sub base uncompacted and compact it the day before a begin the bedding layer, or does it not really matter either way? Will leaving the sub base 'loose' for a couple of weeks do any harm? There won't be any traffic on it during this time.

Well thats about it, 3 questions each with various sub questions!

Thanks in advance.

[Tony McC]

1 - read the sub-bases page

2 - read the sub-bases page

3 - guess what? Read the sub-bases page

[mattrgee]

Although there's a lot of useful information of the sub base page, I can't find any direct answers...

Any help appreciated.

[Tony McC]

1 - it's impossible to give a definitive answer because different materials compact in different ways. Further, the moisture content and the force of the compacting equipment can make a significant difference. 100mm of gritstone Type 1 may well compact to 75mm, but maybe you only need 90mm of a granitic Type 1, or 110mm of a limestone. Trial and error is the only way to find out what's needed on your site.

2 - yes.

3 - compact immediately after laying. Leaving it uncompacted invites all sorts of crap into the voids. Immediate compaction tightens the surface and gives the whole structure some degree of protection from contamination.

[mattrgee]

Thanks for your time Tony, I really appreciate your help.