Patio to wall junction - help please on building regs

[Hilldes]

Hi all,

 

Need some help please to interpret building regs.

 

This relates to a problem I have with a warranty provider in this thread.

 

The warranty provider is quoting this:

 

"The Building Regulations Approved Document C – Site Preparation and Resistance to Contaminants and Moisture includes ways in which internal and external walls must be designed/ constructed in order to resist moisture from the ground. Section 5, Clause 5.5b confirms ‘if the wall is an external wall, the damp-proof course should be at least 150mm above the level of the adjoining ground (see Diagram 8), unless the design is such that a part of the building will protect the wall;’"

 

I want to ensure that any furniture purchaser could have reduced distance between DPC and finished external ground level for a patio or level threshold to Bifold doors for example. With the trend for level thresholds at patios, there must be something in the building regs that support this option? For example, with suitable linear drainage channel at the patio to wall junction.

 

I believe there is also a reg on the maximum step down from and external door to external finished ground level - is this less than 150mm?

 

Help would be much appreciated to close off this saga with the warranty provider that has been ongoing for months.

 

 

[nod]

If you haven’t started a get a new warranty provider Some ask ridiculous questions and set unreasonable conditions 

 

The level threshold is an easy one 

Where there is a level threshold you simply step the dpc up the wall at either side 

[Canski]

and providing a cavity tray to this area is recommended

[Radian]

1 hour ago, Hilldes said:

Clause 5.5b confirms ‘if the wall is an external wall, the damp-proof course should be at least 150mm above the level of the adjoining ground

Like @nod say's, step up the DPC either side of the doors. Some knuckle heads think a door is a wall. It isn't and it's not bothered by rain splashing up unlike masonry.

[Hilldes]

Thanks @nod @Canski and @Radian. Please could you point me at the relevant text in Approved Documents, or LABC, NHBC etc. so I can quote back to warranty provider.

 

On changing the provider, my only option I think would be a retrospective warranty as the build is complete and this one condition is the last one to resolve - although it has taken a number of months so far to try and resolve it.

[Mr Punter]

Can you drop the level of the paving adjacent to the doors so it is 150 below DPC?

[ETC]

1 hour ago, Radian said:

Like @nod say's, step up the DPC either side of the doors. Some knuckle heads think a door is a wall. It isn't and it's not bothered by rain splashing up unlike masonry.

Absolutely - the door isn’t a wall. The DPC should be 150mm above the ground to EACH side of the opening. This is achieved by the brick layers stepping the DPC up at external each door location. When they forget to do this an acceptable solution is to install an ACO linear drain across the door location.

 

A patio is a different story - where a patio is retrospectively built at FFL the DPC needs to be 150mm - minimum - above the level of the patio in the external wall. I see this all the time when the builder doesn’t know where a patio is going and the DPC is put in too low.

Edited December 10, 2022 by ETC

[Hilldes]

19 hours ago, Mr Punter said:

Can you drop the level of the paving adjacent to the doors so it is 150 below DPC?

 

Thanks @Mr Punter I don't plan to do this - I will keep all paving >150mm below DPC. I just want to ensure the warranty condition does not exclude reasonable options for potential future purchasers. I see Paving Expert has some 'work arounds', but I think not technically compliant with building regs.

[SBMS]

I’m not sure if I completely understand your detailing but thought I would add that I asked my BCO (and combined warranty auditor) about this today, as we are building a level threshold for our patio and 8m of sliding doors on rear of our build. His

response was that the 150mm below DPC was not relevant for a door aperture and that an acceptable detailing of a slot drain abutting the doors would be written up in his report as satisfactory. He did however say that it wasn’t his call as to whether the warranty provider imposed a restriction on the policy - though he’s not aware of ours doing so as it is a common detailing. He said with his building regs hat on he was more than happy signing this detailing off. 
 

I asked what would we do if there was a limitation imposed with a future house sale and he said it’d be relatively cheap to get an indemnity to cover this as it is now such a common detailing. 
 

 

[Hilldes]

20 hours ago, SBMS said:

I’m not sure if I completely understand your detailing but thought I would add that I asked my BCO (and combined warranty auditor) about this today, as we are building a level threshold for our patio and 8m of sliding doors on rear of our build. His

response was that the 150mm below DPC was not relevant for a door aperture and that an acceptable detailing of a slot drain abutting the doors would be written up in his report as satisfactory. He did however say that it wasn’t his call as to whether the warranty provider imposed a restriction on the policy - though he’s not aware of ours doing so as it is a common detailing. He said with his building regs hat on he was more than happy signing this detailing off. 
 

I asked what would we do if there was a limitation imposed with a future house sale and he said it’d be relatively cheap to get an indemnity to cover this as it is now such a common detailing. 
 

 

 

Thanks @SBMS

 

On the detailing I think the most challenging part is not the threshold to the door it is the patio to wall junction either side of the door. As others have said the patio can be level with the door threshold either side of the door provided the DPC in these sections of wall is move up my 150mm. I can picture how this works with block and brick built houses but not with timber  frame inner skin with render board outer skin.

 

Thanks for the note on the indemnity option on the other thread - given we all know this is common detailing much better for warranty provider to acknowledge this is established practice (with the right measures in place such as drainage) and add not a highly visible policy exclusion that is clearly just for this property. This may not affect you though if you patio is completed before the BCO completion visit. In my case there is temporary landscaping and the patio will be added later.