What to put below render (over DPC)

[justins]

Hello!

 

Been lurking around here the last 14 months while we converted out 60's bungalow into a modern 3 storey house, with as much passive house spec as we could get (but not even close!). A lurker more than contributor being that I don't know much about much, so it's mostly been researching things. Though realised I've learned a lot over the last year so plan on doing a little post on things I've learned in case it might help others in the same situations!

 

Anyways... requesting some help...

 

We're nearing the end of the project and are struggling with what to put between the ground and the render (is it called a plinth?). It's not all easy straight lines either - some stairs to figure out and a few different types of surface.

 

Builders are suggesting bitumen paint. Looks kind of ok, but means there is no insulation on those areas.

 

We's love to brick or board it but then that would bridge the DPC... so thought maybe batons and then insulation board on the batons... keep air there so there's no DPC bridge... but not sure if that works. Then either render or paint on the board?

 

Brick slips might be good but will be a tedious job around the stairs and would still need the boards and insulation.

 

Assuming we'll have a kind of french drain around the outside up against this plinth.

 

What have others done in this situation, must be a common thing?

 

Anyone with experience of the bitumen paint in this situation? Something about it doesn't sit right...

 

Much appreciate any help and thanks to everyone posting on here with stuff that's helped on our build thus far.

 

Cheers, Justin

 

 

 

 

 

[Radian]

Hi. I used PS cladding to finish my plinths. This cladding was used on other elevations so it made sense in the overal design. It also meant that I could pack the horizontal battens to bring it out to the edge of the sills. I understand that the PS is  made from recycled CD cases!

[Gus Potter]

Much will depend on the amount the finish above overhangs the base course.

 

Will something like this suit you?

 

 

 

 

 

Edited December 8, 2021 by Gus Potter
improved detail !

[nod]

I often put a thin coat of render 

[justins]

12 hours ago, Radian said:

Hi. I used PS cladding to finish my plinths. This cladding was used on other elevations so it made sense in the overal design. It also meant that I could pack the horizontal battens to bring it out to the edge of the sills. I understand that the PS is  made from recycled CD cases!

 

This looks great. Can't find anything looking like that when I just searched for PS cladding. Do you recall where you got it? And you built it out on batons and then onto a concrete board? or the cladding fixes to the batons?

 

Thank you!

 

 

 

[justins]

11 hours ago, nod said:

I often put a thin coat of render 

Does it not just blow after a winter freeze? We were thinking that but the people doing the main render on the house refused to do it because they said it wouldn't last!

 

Thanks!

[justins]

12 hours ago, Gus Potter said:

Much will depend on the amount the finish above overhangs the base course.

 

Will something like this suit you?

 

 

 

 

 

This looks expensive - and complicated as we have a bunch of levels and steel plate I imagine would be difficult  and expensive - just like the upside down render bead idea!

 

Thank you!

 

[Temp]

I think there are special renders approved for use below DPC but i've not used them.

[Radian]

59 minutes ago, justins said:

This looks great. Can't find anything looking like that when I just searched for PS cladding. Do you recall where you got it? And you built it out on batons and then onto a concrete board? or the cladding fixes to the batons?

 

Kedel.co.uk was the place I got it from

I secured short vertical battens every 400mm onto the blockwork with then fixed horizontal battens on top of those. You can get plastic battens to make this last a lifetime or if you're on a tight budget (like me) use recycled roofing battens. ?

 

 

[nod]

2 hours ago, justins said:

Does it not just blow after a winter freeze? We were thinking that but the people doing the main render on the house refused to do it because they said it wouldn't last!

 

Thanks!

 

Often brick slips have been intended below the bead But there isn’t always room I normally use a base coat 7 mil

and sponge it to a smooth finish 

That gives a very hard durable finish 

Your dilemma is more common than you think 

 

[Radian]

8 hours ago, nod said:

 

Often brick slips have been intended below the bead But there isn’t always room I normally use a base coat 7 mil

and sponge it to a smooth finish 

That gives a very hard durable finish 

Your dilemma is more common than you think 

 

I used that to trim another gap I had. I added dye to black it out. Got some sexy black vents in there too but you can't see them...

 

Time will tell if it stays put.

[Gus Potter]

10 hours ago, justins said:

This looks expensive - and complicated as we have a bunch of levels and steel plate I imagine would be difficult  and expensive - just like the upside down render bead idea!

 

Thank you!

 

It's not a metal plate..metal lath.. it is a lightweight mesh, easliy cut, bent and fixed. We often use this on base courses where there is a risk of frost and wet masonry below DPC level, proven to work, no significant bridging of DPC etc.

 

Anyway, glad you have ruled it out. Often part of the design process is identifying what you don't want and this makes it easier to narrow the field.

 

Let us know what you go for at the end of the day as interested.

 

 

 

 

[justins]

16 hours ago, Gus Potter said:

It's not a metal plate..metal lath.. it is a lightweight mesh, easliy cut, bent and fixed. We often use this on base courses where there is a risk of frost and wet masonry below DPC level, proven to work, no significant bridging of DPC etc.

 

Anyway, glad you have ruled it out. Often part of the design process is identifying what you don't want and this makes it easier to narrow the field.

 

Let us know what you go for at the end of the day as interested.

 

Ahh - I misunderstood. Appreciate the input! And yes, figuring what you don't want is often as helpful as figuring what you do!  Cheers!

[justins]

On 09/12/2021 at 11:45, Radian said:

 

Kedel.co.uk was the place I got it from

I secured short vertical battens every 400mm onto the blockwork with then fixed horizontal battens on top of those. You can get plastic battens to make this last a lifetime or if you're on a tight budget (like me) use recycled roofing battens. ?

 

 

 

We've gone for this - just ordered the black v boards from Kedel  now just hoping we can get the urgent bits done before the builders all break for xmas!

 

Thanks for the suggestion! J.

 

[Radian]

You're welcome. What's their delivery going to be?

 

The best way I found to cut it was with a TCT blade with lots of teeth otherwise spec'd for aluminium. Obviously chop saw flies through it but you can easily saw by hand or any other kind of tooling you would normally use with wood. For scribing to irregular butt-joints the jigsaw is OK but has to be variable speed set to almost the lowest. Any faster and the kerf of cut just melts back together - as though you'd never cut through it! Oh, and WD40 (or other kind of silicone spray) is good for keeping blades lubricated and polishing the plastic if it gets scuffed.

 

I like this stuff because it's 100% PS, unlike some composite cladding and because its colour is all the way through not just a surface wrap like all the UPVC alternatives I found. The only downside is its fire performance which I'm sure is absolutely dismal.