How would you repair brick plinth?

[AndrewB]

Hey guys,

Ive been doing some repairs and improving drainage along the side of my property. I've been in contact with some builders and plastered and frankly give up. Can't get anyone to do the job. I usually take on most things but previously drew the line at plaster and bricks... Guess I'm going to have to do it myself!

The level of the drive was way too high so going to tidy it all up and add a French drain.

Anyway, my question is about the brick plinth (think that's the name). As you can see, it's in bad shape in a few areas. The bricks which used to stick out are completly crumbled away at the front of the house. Those that remain 'under the wall' are crumbly and cracked also.

I'm wondering; can I make some sort of lime mortor and remake the plinth with layers of mortor? If so, what would the recipie for the mix be?

Do I need to replace the bricks first by digging out the old ones? If so, what would the recipie for the mortor between the bricks be? (same as the 'render'?). But scared of removing bricks! Any advice appreciated!

I just has another area repaired by a proper Brickie, so have half a bag of nhl 3.5 and 3 bags of plastering sand at the moment.

Thanks for the help!

 

[malcolm]

It's worthwhile getting rid of the rest of the concrete plinth. The bottom of the outside walls should be breathable - if you let the water out to the outside there will be much less left in the wall to cause damp inside. If the outside is ventilated to a couple of bricks lower than internal that would normally be enough to dry the wall before it gets above internal ground level. Careful not to prevent that ventilation with french drains. They are a water management system not a damp management system.

Choice will be repoint the bricks with lime and leave them exposed or add a lime render plinth. I would tend towards leaving the bricks exposed.

You can remove stretcher bricks easily by working around the mortar with a hammer and screwdriver until they become loose. Pull them out, clean up the rest of the old mortar, put a big dollop of lime mortar in the hole then tap the brick in and let the mortar come around the edges. Use a pointing finger to force lime around the brick until the joints are fully filled.

Looks like your place has suffered cement repointing so there aren't many clues to the mix. I tend to use 1 part NHL 3.5 to 2.5 parts sand, and the sand I use is itself a 50:50 mix of builders sand and sharp sand.

Bricks, pointing and rendering are very much DIYable and are quire rewarding.

 

[AndrewB]

Thanks Malcom, much appreciated. Would the lime mix be the same for repointing and rendering?

I've a bit to think about here.

I don't think the top row of bricks are actually stretcher bricks. Will take a closer look tomorrow, but I think those bottom rows are all offset 'normal' bricks and the angled bit at the top is render. Not sure that matters, but thought I'd mention.

I think I'd like to ultimately have a rendered surface to match the front of the house (although, colour matching is going to be another problem... Sandtex type stuff on the front and other side of the house).

If so... Should I still repair the bricks and have a thin layer of render... Or is it generally OK to have a deeper render (e.g. 50mm in places)?

Suppose I could do the worst of the bricks

Probably worthy of another post, but pretty sure the pebbledashed render is concrete also...fizzes just a little in vinegar...

 

[malcolm]

Render would be OK. Worth knocking the cement out of the pointing and re-pointing first but you could use the render mix for the pointing. The choice of sand dictates the surface finish (finer sand for a fine finish) and the depth you can apply on one go. It's common to use a sharp sand to build up thickness in 1/2 inch increments then finish with a finer sand.

Sands can be a lottery from builders merchants. I bought some rendering sand (a finer sharp sand) which turned out to be a washed sand (no small bits). The render failed on my first attempt and I ended up mixing it with builders sand to get the mix of grain sizes needed.

Breathability will be more important than strength so a lime putty based mix might be worth considering. NHL wouldn't be quite so breathable but a lot better than cement.

 

[a twig]

Very good point on sand Malcom, the stone mason working on our ashlar brought his own range of sieves and drying trays and would painstakingly sort out the grades he needed at the start of each day

 

[AndrewB]

Thanks both.

I remove the cement down that side of the house and give a small area a go with my nhl 3.5 and plastering sand to see how it goes.

Got my loft to sort out first (see other thread lol). Will report back with how it goes.

Do I just send a stamped addressed envelope to claim my level 1 lime certificate once I've posted the photos?