Wet conditions wet screed sand effect on compactin - Setting a 45- herringbone & jointing

[nobby]

Hi all, would love some direction on the following.

I am block paving a 6 x 4.5 metre section of my drive to stand cars on with 60mm blocks. I have put kerbs in and the base of MOT type 1 with a TDP geo-textile membrane over a sub grade of light clay soil. I will be doing the screed and laying of the blocks this coming weekend (weather permitting). I have put up a cover to keep the wet out, so can do some work if raining.

· As the weather conditions are generally wet and sand deliveries are quite wet, could you advise when pre compacting what affect the damper sand could have. I am using a medium wacker plate i.e. 84 kilo 16.5 kn with a plate size of 600 x 400 mm. Would I pre compact with just 1 pass, 2 passes, or even more.
My drive slope at 330 mm over 4 metres then 90 mm fall over last 2 metres to dished gully all with a fall of 75mm to the right and the drain. 50 x 150mm kerbs to the 3 sides and gully forming 4th kerb at boundary wall of house a d door entrance, On the 3 kerbed sides it does not matter if the finished level is high or low, but at the gully end level or high is OK but not low. So I don’t mind pre-compacting slightly more the laying bed.

· Jointing, in the site you mention that if it is damp or wet when the jointing is done, that there is a method of wet jointing. Could you explain this, as I have not found it on the site?

· Setting out a 45-degree herringbone. In the site you give a measurement of 215mm from the side base line to start the first course. Is there a set measurement from the bottom base line kerb to start from?

· My sub base has been down now for just over a week, and the weather as been wet over the last week. The other day I topped up the Type 1 to the correct level and run the wacker plate over the whole area again today, this produced a few wet patches form through the vibration of the plate bring water / fat (as in concrete) to the top. Should I let the base dry out fully (as the type 1 moves on the top a little within these wet patches) before I screed and lay the blocks
???

[matt h]

more passes better compaction, once rain stops if ever compact again before sand then compact again, again you'll know when its compact enough as the sand will quit moving. There is no need to let the base dry out fully imho, as the passes should resolve that issue, the sand will take up any discrepancies, and as you are using 60 mm block thre shouldnt be a problem. You'll need a rubber mat to vibrate over the blocks to prevent dragging on the block surfaces. tony does good plans for block /slab layout , which will ultimately save you a lot of agrevation imho see main site for details:)

[nobby]

Hi Matt
Thanks, should I pre compact bedding layer once, twice or more before levelling the screed to be sure of being level or high by a few mm so water will flow into the dished gully.

[matt h]

Better to be slightly high, i ALLOW ABOUT 7-8MM ABOVE GULLY FOR FINISHED BLOCK HEIGHT. iT SETTLES DOWN AFTER ABOUT 6-12 MONTHS JUST FINE. cOMPACT AS MUCH AS YOU CAN, YOU'LL KNOW WHEN ITS RIGHT BY THE RUN OF THE COMPACTER.. REMEMBER MORE PASSES THE BETTER THE END RESULT. BEST OF LUCK, AND MAY THIS WEATHER END SOON!!!:D

[Pablo]

2 passes at the most with the plate on the bedding sand. Too many passes and the sand is harder to screed. If your boots make a light impression in the sand then thats enough. Then plate the hell out of the blocks once finished and all will be tickety boo.