blocking on an awkward fall

[deefa]

Hi Tony, ive got a bit of an awkward job on at the moment, we are block paving a front driveway that slopes from the road down to the house at an angle of about 25 degrees, this in itself poses no problems as we have set down the fall from road to house accurately to within 2-3 mm the headache is that the drive also slopes away from left to right about three quarters of the way accross due to a difference in dpc,s between the garage and the house itself, in other words if you stood near the top left of the drive and placed a ball on the ground it would roll towards 2 o,clock so we are dealing with 2 seperate falls!...im concerned about the screeding and making sure the joints on the blocks are even and tight where the difference in slopes are so pronounced?? is this just a case of sweetening the changes in the screed?? we have installed 2 pot drains to take care of water run off in the low spots but the slopes Tony the damn slopes !! any advice for me on this one??

[84-1093879891]

It's not uncommon to have to deal with non-orthogonal falls (falls not square or a parallel to the base line) but preparing the screeded bedding layer isn't all that difficult.

You have certain fixed points, such as the dpc level and the threshold level at the footpath/roadway, so these dictate what's possible. I find the quickest way of dealing with this scenario on a private driveway is to establish the soldier edgings/kerb, making sure they are aligned and profiled correctly and then to prepare the bedding layer by using these edges as a guide. Keep standing back from the screeded layer, and checking its profile, levelling or feathering as required to create an acceptable profile.

Only when you've 'sculpted' the bedding layer into a decent looking profile should you start the block laying. Unless there are severe changes in falls, it should be straightforward enough, covering the ground with all the full blocks and then cutting-in as required. However, if you do have sudden or pronounced changes in level, then keep checking the alignment of the blocks as you lay, to keep an eye on any pattern drift that may develop.

The key thing is, as ever, the preparation of the bedding layer. If you get that right, the blocks will follow, with the minimal of persuasion. An extra 10 minutes spent preparing the screed can save hours of frustration later. :)

[deefa]

Hi Tony, thanx for the quick reply..i thought that would be the case but i thought id check if you had a more scientific way of going about it!!...i,ll make sure ive got my specs with me on monday when i start the bedding layer screeding!!!!...this has been one of those tricky jobs so far but after getting in the gulley drains and pot drains today it feels like weve turned the corner and should be finished to schedule by the end of next week...as always we have taken before/during/after pics so i,ll send a piccy when done and you can see if i need to call in on the optician over christmas..eyes dont fail me now

[84-1093879891]

Watch out for frozen sand come Monday - the hard overnight frost that's expected will freeze a crust onto bedding sand, and you can't screed or lay blocks until all that frozen material is gone - either thawed out or scraped off and replaced with unfrozen sand.

[suki]

hi tony im looking to buy a 3 pronged gas burner the type they use for felt roofing this would help out with such frost issues also hopefully drying blocks out so i can get some kiln down and get off a job however finding a burner for the job is proving tough can u recommend a make and model??

[84-1093879891]

I've no idea what make/model ours is, and there's no way I'm going out there to clean off all the pitch and crap that's become encrusted upon it over the years, but I know we got it from Greenham Trading - or was it AG Strachan?
Anyway, you should be able to get one at a Contractors' Merchant or try a Roofing Merchant, as those burners are a popular item with the roof monkeys.