Laying a patio (for a novice)

[rh2205]

We have some sandstone paving we are laying, we are also building up the threshold to be more in line with the DPC so there isn’t such a drop from the patio doors, as such we were thinking of putting in some kind of aco drain to prevent damp, is this the best way or is there a cheaper/easier to install alternative to this option? Do we literally just set this aco drain in concrete once we’ve hopefully got the right levels? The house is 16m wide so it’s quite a wide patio!! Probably making it even harder for novices to lay correctly..

 

Any tips or pointers most appreciated as whilst we might not start until the weather thaws a little now we do want to get everything we need ready and have a bit of a plan on how the hell we do this.

Edited December 6, 2021 by rh2205

[Dave Jones]

you really need 150mm below DPC unless you have a tray.

[rh2205]

@Dave Jones So there is no way to achieve this it would be like a 250mm drop from the flush floors inside if we used 150mm below as bench mark. We were hoping to bring it up just below dpc to get the drop nearer to 150mm. We have some very wide bi parting doors and I don’t see how a step would work. Just to add it’s a refurbished 1960s place.

Edited December 6, 2021 by rh2205

[Dave Jones]

doors are generally ok to flush upto  as there is no cavity above dpc to let the wet in, as its a door! Although you do need to pay attention to the door/wall junction.

 

Some use a gravel channel next to the house, as its splashing water your trying to avoid soaking the brickwork above DPC and therefore letting damp into the cavity. You can get some paint on waterproofer as well.

 

We allways have a tray 600mm above dpc on our last two homes that way you can safely lay patio flush to finished floor level inside and have no worries about damp getting in. 

 

 

[Radian]

20 minutes ago, Dave Jones said:

you really need 150mm below DPC unless you have a tray.

What's the thinking behind the use of tray in this case? I understood that the 150mm below DPC was to prevent rain splashing up or being wind-driven up to the wall above DPC.

Does the tray simply act like moving the DPC up to the recommended height?

Of course, in level thresholds, the door itself isn't bothered by any of this and a linear drain at the threshold is the standard solution.

If all you were trying to do is, say, bring the patio level up to 100mm below DPC then might not a linear drain suffice? This would positively drain the sensitive area and while not eliminating splashing entirely, it would reduce it considerably.

Quote

 Do we literally just set this aco drain in concrete once we’ve hopefully got the right levels? The house is 16m wide so it’s quite a wide patio!! Probably making it even harder for novices to lay correctly..

I've put in 10m as a complete newbie and I'd say it's quite doable. I also laid 106m2 patio over the course of the year and was actually a bit sad when there was no more left to do!!!

[Dave Jones]

a vertical cavity tray effectively moves the level of DPC higher. Very handy if your on sloping ground for example and you want to bank up against the building.

[Radian]

12 minutes ago, Dave Jones said:

doors are generally ok to flush upto  as there is no cavity above dpc to let the wet in, as its a door! Although you do need to pay attention to the door/wall junction.

 

Oops, didn't see your post go in before mine. I see we are in agreement.

[Marvin]

1 hour ago, rh2205 said:

We have some sandstone paving we are laying, we are also building up the threshold to be more in line with the DPC so there isn’t such a drop from the patio doors, as such we were thinking of putting in some kind of aco drain to prevent damp, is this the best way or is there a cheaper/easier to install alternative to this option? Do we literally just set this aco drain in concrete once we’ve hopefully got the right levels? The house is 16m wide so it’s quite a wide patio!! Probably making it even harder for novices to lay correctly..

 

Any tips or pointers most appreciated as whilst we might not start until the weather thaws a little now we do want to get everything we need ready and have a bit of a plan on how the hell we do this.

In my humble opinion it's worth checking info on A J McCormack  paving expert site before you start. look up "sandstone paving",  "patio drainage" and so on for tips 

[rh2205]

So we wanted to bring the patio to about 50mm below the DPC and was thinking of using an aco drain (or linear drain). We can’t change the cavity tray the building works are done plus it sounds pretty costly on an existing house, we had initially considered painting some dpc stuff on the brickwork with a 100mm wide pea shingle channel but then didn’t think this would be as effective at preventing damp as a linear drain. One of my relatives just had a damp survey (admittedly on a older property with solid walls) and the surveyor said do not reinstate with a french drain but use a linear drain as they often cause damp and lead to more water sitting against the wall (their ground levels are already raised and cannot change them). The garden slopes away from the house.

 

So will an linear drain lead to more likely chance of damp than pea shingle? I mean I guess this work isn’t recommend but our EWI insulation is overhanging by 110mm so maybe the splashing thing is quite low risk on the brickwork below that is exposed?

 

I should add if we can’t bring the patio up to 50mm below dpc along the back of the house (we have a lot of not very far away from each other patio doors) then it will mean quite a drop when going outside as it’s already 150mm as it stands if we go with 50mm below dpc.

Should add also our 50mm cavity is filled with eps beads, maybe the overhang with the EWI and the number of openings makes this level change all very low risk.

Edited December 6, 2021 by rh2205

[Dave Jones]

150mm below dpc (2 bricks).

 

Maybe easier to make a feature step for the doors ?

 

a linear drain wont stop rain splashing above the DPC, you may be ok and it not get too much weather  on it to worry about then again you may not.

[rh2205]

So we have 3 fairly big (one huge) opening on this face I don’t think we can make a feature out of steps! The EWI is set 100mm above dpc (I know this is totally wrong but it one part of the house dpc was set at a different level due to an extension). 

Edited December 6, 2021 by rh2205

[rh2205]

We can live with 1 brick below dpc and the floors are set at dpc level. Is a linear drain or pea shingle the least risky as I don’t think we can move to a step option so we will have to hope for the best. That means the patio will be just below the silver door strip on the image.

Edited December 6, 2021 by rh2205

[rh2205]

I know we should have mouldy skirtings anyway from the EWI issue haha, but these seem fine so far this winter but then maybe the filled cavity has helped… or we could go digging crazy and try and put in a small amount of foundation EWI in before we do this work if that’s further likely to negate the risk of damp. But I don’t think we are willing to budge too much on the patio levels as our large garden has already had levels adjusted to meet this patio level

Edited December 6, 2021 by rh2205

[rh2205]

Actually scrap the foundation EWI our cills won’t work with it and we aren’t going to pull out all our doors now, I think if we do a brick and a half the drop is about 200mm from internal floor as I’ve just measured which we can live with so then its just whether the linear drain is the best method to minimise damp risk. Hopefully our lawn has sunk a bit since being levelled…

[Roundtuit]

I used aco galvanised slot drains in front of bifolds leading on to the patio (only a ~4m run), 1 brick below dpc. I ran a bead of sealant between the slot and the brickwork afterwards to stop surface water going down between. Seems to do the job. 

[Radian]

Galvanised up to the sills would suit those doors which should be OK with splash, it's just the underside of the EWI. Maybe you could build up to the underside with more black bricks (flush with EWI) but leaving gap to foundation at rear & EWI above for sealant? Probably a daft idea!