Will soon be laying 25mm thick limestone flags on a 2metre wide patio it will have very light use and there is approx 75mm of compacted type 1
But due to levels and other factors to maintain the 150mm below DPC I need to make the bedding layer about 20mm thick will this be OK? Also will a ratio of 5 to 1 be OK or will it be best to add some building sand to make it more mortar based? Your suggestions as always will be much appreciated.
Thanks Ian
wideboy neither your base or your bedding are deep enough. If thats what you've got to work with then i would either reduce the base so you would have more bedding or pinch an inch off the dpc. Regardless of what you do you need 40mm of bedding under the flags.
Paplo
Thanks for the reply but I'm confused just looked at Tonys guide to layer flags and it states. "Bedding layer
Flagstones can be bedded directly onto either:
a coarse, grit sand bed, approximately 40mm thick
a cement bound bed approximately 20-40mm thick"
and that a base layer is not necessary if the sub soil is firm.I can't really pinch any of the base as there is the footings of any old wall running across the base about 3/4 of the way out and short of dynamite I don't think it's going to come out bloke that laid the old patio must have built bomb shelters going by the size of it!! Help please!!Dont want to cock it up but dont really want to breach the 150mm DPC rule.
Cheers Ian
Hi Ian the paving you are laying requires a mortar joint so it must be laid on a sand and cement bed. There are flags that can be laid without a mortar joint and they can bedded on sand although for most domestic jobs it's best to lay them on sand and cement just for peace of mind. Because your subbase is so thin it's best to go with a thicker bedding 20mm isn't strong enough. With regards your DPC without looking at your house it's hard to tell but 99 times out of a 100 you will be perfectly ok to lessen it to 120mm which would give you a decent bedding thickness. If you can fall the water away from the house all the better but if you can't then you could do with an acco type drain to keep the water off the bricks.
Paplo thanks for the advice.I was planing on using geofix or marshalls to joint up will be using 25mm calibrated limestone and can get away with 1 in 80 fall just a bit worried about DPC thats all is the 150mm rule cast in stone or just good practise? what would be the absolute minimum you would recommend?
Cheers Ian
Wideboy wrote:Paplo thanks for the advice.I was planing on using geofix or marshalls to joint up will be using 25mm calibrated limestone and can get away with 1 in 80 fall just a bit worried about DPC thats all is the 150mm rule cast in stone or just good practise? what would be the absolute minimum you would recommend?
Cheers Ian
Wideboy wrote:Paplo thanks for the advice.I was planing on using geofix or marshalls to joint up will be using 25mm calibrated limestone and can get away with 1 in 80 fall just a bit worried about DPC thats all is the 150mm rule cast in stone or just good practise? what would be the absolute minimum you would recommend?
Cheers Ian
GEOFIX is total rubbish,not even good landfill,
Marshalls weatherpoint 365 is no problem on patio's i've used it alot MSH
Right Ian listen up. Increase your bedding to 40mm and the paving side of things will be fine. If your base bedding and flag depths added together bring the finished level to your 150 DPC then adding 20mm to the bedding to make it 40mm will give you 120/130mm below DPC and that should be fine. The DPC rule is best practice but sometimes your hands are tied and you have to break it and like I said it's almost always going to be fine. If you're going to use a ready mixed pointing compound then I'd recommend Rompox or GTFK over the Marshalls. If you can post a picture of the house it may be easier to tell what your options are.
Paul.
Cor Paplo you sound just like my Mrs "Right listen up"!Have just had a remeasure and can work to your sizes without compromising the 150DPC Rule! .
Thanks for your advice mate Cheers Ian
