The Brew Cabin

Posted: **Tue Feb 24, 2009 3:26 am**

Gentleman,

I have a dilemma. PLEASE help.

I have spent a considerable amount of time looking through the pages on the site, in particular, screeding and related pages. I am not sure if I know the answer to my own question, or not. With everything renovation or building, generally speaking, if there is a harder way to do something, I will do it, in the interests of getting a better quality, or better looking, job. But I am looking to make a compromise on paving and I am not sure if it is only a compromise or a silly mistake that I will regret.

Here is my situation.

I have been building a storage area underneath my house, around 5 metres x 8 metres, and only a bit over 1 metre (4 feet) high. So no standing. It is only accessible through the lounge room. I have spent some time levelling, rendering, and painting, and now plan to lay some cement pavers, 450x450x50.

Here are some pics of the area: http://wagnon.net/pavers/index.html

The house is old, and the entire suburb in Australia is a sand pit, 2 or 3 miles from the beach. So the sand is course, I believe (ie as compared to building sand).

My issue is that I am loathed to remove the sand that is down there, put a base down, and then replace it with new sand. As I say, there is already sand there, and it is only accessible via the lounge room. There are also a number of other special circumstances, as compared to most paving situations I believe.

The area is technically "inside" and so will never be exposed to rain.
You can't stand up (as I say it's less than 4 feet), moving around is on hands and knees, and so there will never be a lot of traffic down there.
It is impractical (and I not sure even if it would be possible) to get a compacter down there.

Laying the pavers is going to be physically demanding. So I want to get this right. I have asked one contractor to look at it, but he walked away.

My compromise is that I am considering screeding off the sand that is there, and laying the pavers. I have a very good laser level and with the advice so generously provided here on this site, I believe I can do a good job. But that means no sub-base, or aggregate underneath the sand, which I think is in greater depth (to hard compacted sand) in some places than others. But the outer walls will certainly prevent any "spreading".

It really is a hard thing to advise on, I suppose, unless you see it. But I am not sure.

This is a long request. Sorry. Any response, however short, will be greatly appreciated.

Regards
Nic

PS. As an aside, the only other issue I have is whether my circumstances would suggest an obvious answer as to whether to use a cement based grout, or a treated pointing sand, or something like romex. The pros and cons of this are well discussed on the site, but then this is mainly considered in "external" applications I believe. I suppose in the back on my mind I'm worried that a paver will sink somewhere, and the non-cement based solution will be easier to remove if I have to lift some pavers. (I just can't see the pavers sinking. They are so solid and heavy.)

PPS. Regarding the site: what an extraordinary achievement this communication is. Voluminous knowledge, imparted with such detail and sophistication, is wondrously inspiring. I am sure it has made a positive impact on the quality of paving work worldwide. I don't just mean in terms of DIY, but with enabling "clients" to ask better questions, or be better specifiers perhaps, thereby motivating paving professionals to do better work (or stopping them cutting corners!). Hearty congratulations to you. One last point. I am sure you have considered and rejected the notion, but I would be very happy to see some Google AdSence ads on the pages. I wouldn't compromises the entity of the communication at all, I don't think.

Posted: **Tue Feb 24, 2009 5:49 am**

was wondering if money was an issue, because maybe you could pump in some self levelling screed? if not i would be tempted to lay on that sand. going to be a difficult job, good luck

Posted: **Tue Feb 24, 2009 7:21 am**

if its virgin sand and well compacted naturally, i.e if you can't push your finger in more than an inch then you'll be fine.

water makes a very god job of compacting sand, probably not got much of it in oz but done jobs where we have left the tap on all night on sand back fill and it has made it like concrete.

if not then hire a small whacker like this one use with the handle folded down

its nasty work but it'll get the job done,

gi

Posted: **Tue Feb 24, 2009 11:37 am**

Well-compacted, naturally-occurring sand normally has a relatively high CBR, and the coarser the sand, the higher the CBR. I'd hazard a guess that you have a CBR in excess of 20, which would be wonderful if this were a standard external paving application.

However, this is internal, so highly unlikely to take any vehicular traffic, which means the construction strength need not be as high as that for a typical external application.

I'd go with Sean: if the sand is 'stiff' and difficult to penetrate with a finger, I'd be happy enough to use it as a sort of combined sub-base/laying course. I'm assuming there is some form of robust restraint at the edges which will limit the potential for movement or rotation, so with that in place....screed away!

As for the jointing, I'd just use a standard KDS. Lay the blocks, scatter the KDS, brush in what you can, then use a rubber mallet to 'settle' the blocks and persuade the sand into the joints. As this is merely a storage area with not real traffic (either foot or vehicular) there's no great pressure on the pavement, and if there happens to be a couple of millimetres difference between two blocks, it's hardly critical!

Posted: **Tue Feb 24, 2009 8:08 pm**

Sorry just had to add a quick note. Do not use any Petrol/Diesel engined machine in a confined space like this. Danger of death!!!! The fumes produced are toxic, only use in a well ventilated area.

Posted: **Tue Feb 24, 2009 10:16 pm**

Yes, I was about to mention that Clive; a guy lost his life at a Rugby Club not too far from me running an engin/pump indoors. The invisible killer.

Posted: **Wed Feb 25, 2009 12:34 am**

Gents,

Thanks to all. Much appreciated.

Unfortunately, the sand is not as stiff as would prevent me sticking more than a finger well down into it. In *some* places, generally toward the middle. (I expect because near the walls the sand has gotten wet at various points over the years.)

However as there are walls on all sides, spreading is certainly prevented. (As per the above URL/pics.)

I think I've certainly got what I need though, ie with a bit of trial and error, common sense, laying on what I have is not irresponsible.

I did find a small compactor at a hire place nearby, and you know, I never thought for a second about the petrol issue. It is a petrol engine. If I can't get a result I'm happy with, I might give it a go with some ducting and a fan that I have, and a see what happens.

Tony McC: KDS (presumably with one of the additive products to make it go hard) is excellent advice and will be much easier. The alternative would have been, for me, to treat the exercise like grouting tiles. And the KDS option makes for much easier application, and easier repair if any sink slightly, too!

Thank again gents. Much appreciated!!!!!!!

Regards
Nic

The Brew Cabin

Screeding in difficult inside application