Slab colour change

[edisonuk]

Why have the slabs changed colour. I had them laid 5 months ago. They are the cheaper brand of the marshalls.

Also, you will see that the bottom of the garage below DPC gets wet, during prolonged rain. It is slowly drying out now. It has acos fitted. Any ideas how I can stop this problem? Here's the pic:


https://photos.google.com/share....VdDdWt3

I am not very good at adding photo's to this sight. Seems tricky

[country boy]

tony you answered your own question about discolouring(cheap concrete flags) and patio should be 150mm below dpc,but looking at your picture i woud'nt worry too much as its only single skin garage with dpm in concrete floor
jim

[edisonuk]

Do you know why the bricks appear to be wet there?

Thanks for the reply. I was thinking of sealing them.

[edisonuk]

Oh and why does parts of the pointing stay wet, even when it has been really dry.

[country boy]

It could be a number of reasons as long as dampness stays below dpc i woud'nt worry about it,as for pointing staying damp it can sometimes take a while to dry out in certain areas especially in shade, again don't worry about it as long as water is not pooling. I have identical patios front and back one in sun one in shade the one in shade takes far longer to dry and has damp areas most of the time.
jim

[edisonuk]

Thanks Jim. Great feedback. Appreciate it.

[lutonlagerlout]

as said those bricks are below DPC so likely to be a bit wetter than the ones above,this is common
the slabs look alright
cheers LLL

[Tony McC]

The colour variation is differential curing - See FAQ - and it's uncomfortably common with these cheaper flags. Manufacturers spend good money on special additives to keep it to a minimum in their premium products, and that's part of what you're paying for with such products, so, with the so-called "budget lines" this is what you have to expect.

The previous posters have addressed the questions about damp and pointing. It's less than ideal but, on such a project, nowt to worry about too much.

[edisonuk]

Thanks for the link Tony. Really interesting. I plan to seal this today.

I had someone out to look at the paving and they said that the base maybe holding moisture as the ground below is clay. This is likely the cause of the wet bricks below DPC. They said? Like you guys, that there was nothing to worry about and that it will dry out overtime.

Hopefully my slabs will go back to the original colour Nd those bricks dry.

[edisonuk]

Last question Tony. I know everyone has said not to worry about the wetness against the garage wall below DPC. However, it does worry me. I need to stop worrying however...

I know the ground is clay. I thought the acos would solve the problem. What is the resolution to this as clearly the acos have not worked?

It happens when it rains heavy. But takes a while to dry out. So whilst everyone else has seen wet bricks dry out on the estate after the weekend. Mine are still wet.

[Tony McC]

If the damp in the bwk is coming up through the concrete floor of the garage, then I'm not sure how the installation of a linear channel drain would resolve the issue. They can only take in water from the surface, whereas your damp is coming from the ground.

Only a filter/fin/interceptor drain could help in that situation.

[edisonuk]

Hi Tony thanks. I think it is definitely coming from the ground.

Will these bricks be able to cope with the long spells of wetness?

Otherwise I will have to take remedial action.

Cheers.

[Tony McC]

That would be a question for Mr Lout. He'll probably know just what type of brick that is (LBC?) and it's permeability rating. Over to you, Mr Lout....

[lutonlagerlout]

if they are LBC London Brick Company then you could have problems as their facing bricks are not rated for work below DPC and will spall given time
hard to tell from the photies
generally we try to use LBC commons or class B engineering bricks below ground as these are rated F1

same reason mortar below DPC must be 3:1 as opposed to 5:1 above ground

LLL

[edisonuk]

Thanks again. This is very useful.

I had a really good chance to study what was happening yesterday as it was raining a lot here!

Although I thought it was a myth before, I am almost 95% certain that the wetness found along that bottom row of bricks is caused by splash back and water tracking along the concrete at the back of the acos. The wall is facing the driving rain, so it always rains heavy towards this wall.

You could see on the drier bricks the rain splashing and getting wetter. Internally the brick is dry (inside the garage), so it is the external face which is wet. I would expect damp from the ground to effect the front and back???

Finally - the wall is dry under the door sill. This is the same under the patio doors too. Which would suggest that the overhang is protecting the bricks below from the rain falling and then splashing.

So final questions - Would you conclude something similar to me? And would a brick sealant be an appropriate course of action?