Expert help required please. - Noobie asking questions before new patio

[Splinx]

Hi Everyone,

Please can you help me. I have an existing patio that falls 1:80 towards the house and has a 50cm pea-shingle bed against the house. I believe that the DPC line is 75cm above the shingle (1 brick lower than the air-bricks).

The missus has never liked this as it looks unsightly and get's filled with mud and has asked for paving right up to the house.

From reading this excellent article on dpc, I believe that I can have a 20-30cm shingle with paving sloping away from the house OR an ACO drain against the house.

What I do not understand is that the article explains that the reason for the paving gap is primarily to stop rain splash-back and so I don't understand how an ACO dxrain that is just 12.5cm wide is okay.

My ideal preference, for various reasons, would be to have a small 10cm bed decorative stones around the edge of the house with the new patio sloping 1:80 away from this to a new ACO drain that runs between the patio and new lawn. Alternatively, as shown in the picture below, we could put an ACO drain next to the house but due to the conservatory, there would be lots more labour involved (and I cannot even contemplate 45 degree cuts on ACO drains - headache!).

Many other builder websites seem to suggest that having a 4" (10cm) shingle bed against the house wall is sufficient. I'm also seeing absolute tons of pictures where paving seems to not consider drainage at all - are they all mad or am I missing something?

Thanks in advance for you time to read this and any advice you can give.

Sincerely,
Splinx

=== IMAGES ========

* What we have now
* An example of what we would like to do

[Tony McC]

"Many other builder websites...." - so: not paving specialists, then?

The Splash Strip notion has limited potential and relies on it being cortrectly constructed which, sadly, is rarely the case. These "builders" seem to believe that the presence of a scattering of any old gravel over the top of any old crap will somehow magic away any surface water sent in its direction.

A properly constructed splash strip ( https://www.pavingexpert.com/splash_strips ) may be able to cope with a smal vloume of surface water, but it is no replacement for a properly designed and constructed drainage system.

The use of a linear channel (Aco is a brand name) against the house is a drainage system - it intercepts any surface water approaching the property - and, as explained on that page quoted above, it is the invert (base) of the channel that is very conveniently if a little contentiously regarded as 'surface level' for the purpose of Building Regs compliance.

Installing a linear channel is actually a lot easier than you might think. There is a guide on the website and even a 45° mitred angle is not all that difficult if you set up a jig or similar of a workbench (or one of the WorkMate type yokes) to help ensure you get the angles correct.

[Splinx]

Thanks Tony,

Yeah, I by no means profess that the other sites are anywhere near to the level of expertise found here, it's just confusing as a noobie and I thought that I would highlight the varied and conflicting information.

So, you are saying that it's NOT the width of the pea-shingle that prevents the splash-back onto the wall above the DPC line?

The article linked suggests that pea-shingle of 300-400mm from the wall is required but it's unclear if this is for drainage, to prevent splash-back or both.

Ultimately, my main concern is that the a linear drainage solution next to my wall will not prevent splash-back onto the wall above the DPS line if it's only 75mm above the patio.

Has anyone got any direct experience of this type of install and if so, do you have any tips please?

For example, when the DPC is only 75mm above the patio should I implement >

Patio > linear drainage (110mm) > Wall
Patio > linear drainage (110mm) > shingle (200mm) > Wall

Something else entirely?

Cheers,
Splinx

[diyamateur]

Hello David, I have been looking at drainage arrangments myself and i had bought the ACO hex drain kit including down pipe connector, sump unit, and 10 meters of channel just to then string up and get levels and found out my level will be against the house which i tought would not be otherwise as thats how my garden slopes towards the house but as you're i am a noobie myself and didnt consider my kitchen sits way higher than garden level so i could have my patio fall against the house to i am having to return all the channel drain, and i would say you can get the corner unit for ACO hexdrain and theres no need whatsoever for cutting just fits right in and will give you 90 degree angle.
Feel free to have a read through my post :p :pClick here

P.S. if yo do order channel drain make sure you order from right place i had to cancel my order from online store who claimed they're in stock for immediate dispatch but waited 2 weeks then asked for refund and i even asked them if you guys are struggling with ongoing corona virus issue please let me know I;m happy to wait as long as i know whats going on with my order or so but kept saying will be dispatched today evening for 5 days straight.

[Tony McC]

So, you are saying that it's NOT the width of the pea-shingle that prevents the splash-back onto the wall above the DPC line?

Not quite - the so-called splash strip was originally devised as a method of minimising splashback (which was never really much of a problem) and as a cheap way of draining rekativeloy narrow areas of paving, such as access paths.

If it's splashback that worries you: forget it. Even in the torrential showers we've been having this week, the amount of splashing is so minimal, a standard, well-built wall will just laugh it off.

The key purpose of the 150mm below DPC rule to to protect that DPC (and thereby the house interior) were there to be a small flooding incident. The use of a linear channel between paving and property (with no splash strip involved anywhere at all) performs that function (more or less).

So, for your build, all you need is paving:linear channel:house ...no need for any splash strip at all.