Underground blockwork

[elMuppito]

Afternoon

 

My first questions for you all.  Hope you can help

 

 

1. We have concrete poured and now need to build up to DPC.

 

Our foundations are quite deep as there are oak trees close by.   Very sandy (as in pure sand) ground conditions

 

So I have to build up exactly 1m in foundation blocks (300x275x140mm) to match the first course of facing bricks below DPC.  Foundation needs to be this way as I have waste water which needs to pass through the underground blockwork.

 

Problem is I can't see any combination of foundation blocks/engineering bricks which will give me exactly 1m whist retaining a sensible thickness of mortar join.

 

Am I going to have to cut blocks in half longways to hit the right height, or does anyone have any tips.

 

Figures are:

 

6 courses of 140mm foundation block as with 10mm join will leave me with 100mm for the last course

 

With highdsight, another £100 or so of cement would have brought the base up to a level where it isn't a problem, but not much I can do about that now.

 

 

2. Can I assume that most merchents can get anything.  Want to use MKM but they don't have some of the things I need listed.  If I give them a list are they likely to be able to source everything?

 

 

3. Related to the above, A cannot see a lintel listed which will be the same width as the foundation blocks, for the waste water to pass through.  Would it be OK to buy 2 or 3 narrow ones and lay side by side, or do I just need to look harder.

 

Thanks 

 

 

 

[PeterW]

Why are you using foundation blocks ..? And have you bought them already ..??

 

Use standard 7N medium blocks, 215x100 and you need to just cut the first one to take out your camber or roughness in the foundation. So I would cut the first block to 150mm, lay it on a 25mm bed and get it all square and level. 
 

3 standard courses of block will give you 850mm total, last two courses laid in std engineering’s gives you the 1m. Weak mix back fill as you go will be fine. 
 

If you’re not sure about cutting the blocks lengthways then lay 140mm blocks on flat on a fatter bed assuming you have 450mm width to play with. 

 

 

[Mr Punter]

Use a slightly thicker bed and a course of bricks.

 

You can use multiple lintels to get the width.

[Conor]

Use 100mmx140mm soap bars to lay a half height course.

[Oz07]

Is your dpc really tight to 50mm? 1050 is guage so is 975. I'd be suprised if this couldn't be lost underground. 

[elMuppito]

7 hours ago, PeterW said:

Why are you using foundation blocks ..? And have you bought them already ..??

 

Honestly, I just thought that solid blocks seemed like a good idea.  I was also matching the existing part of the house which was built on foundation blocks.  But if it makes no difference from a strength perspective then I suppose there's no point matching something which won't be seen.

 

I've not bught anything yet.  Just working out my quantities so I can go and see the builder's merchant.

 

7 hours ago, PeterW said:

Use standard 7N medium blocks, 215x100 and you need to just cut the first one to take out your camber or roughness in the foundation. So I would cut the first block to 150mm, lay it on a 25mm bed and get it all square and level. 
 

 

Just priced this up.  Even with the extra for the mix, I reckon it's half the cost.

 

Thanks for this, I think this will do it.  Will run past the BCO tomorrow.

[elMuppito]

7 hours ago, Mr Punter said:

You can use multiple lintels to get the width.

 

Great, thanks.

[elMuppito]

6 hours ago, Oz07 said:

Is your dpc really tight to 50mm? 1050 is guage so is 975. I'd be suprised if this couldn't be lost underground. 

 

Could be my maths.  I looked at an extra course which should be 1050, but worked out I'd need a 2-3mm bed for that to work at exactly 1m.

 

You can see the first two courses of facing bricks, and I just wanted them to line up perfectly.  Really wish I'd just have poured the foundation to the same height now

 

Def going to look at using standard blocks and backfilling though, I think that will do it.

 

Thanks

[Brickie]

Have you checked the levels right round with a dumpy or laser? 
if it’s just 10 mm lower then a block laid flat to kick off would give you 110mm,leaving 900mm. If the footing rises up in places,the Brickie can switch to laying engineering or concrete coursing bricks in those areas for the first course. 

 

[PeterW]

7 hours ago, elMuppito said:

Just working out my quantities so I can go and see the builder's merchant.

 MKM do a self build account and they also do decent pricing when they know you want quantity. Get a full list sorted, go meet the branch director over a coffee and show them your plans. 

I have accounts with MKM, TP and Buildbase and probably put 90% of my stuff through MKM as they out price and out deliver the others. 

[elMuppito]

6 hours ago, Brickie said:

Have you checked the levels right round with a dumpy or laser? 
if it’s just 10 mm lower then a block laid flat to kick off would give you 110mm,leaving 900mm. If the footing rises up in places,the Brickie can switch to laying engineering or concrete coursing bricks in those areas for the first course. 

 

 

Thanks.  I haven't yet but it seems pretty level with the pins all round and they were perfect.  That said a rise or fall of a few mm would be impossible to see without measuring.

 

I'll check tonight - need to go on hedgehog duty in the trench anyway, all the hedgehogs around here are either adrenaline junkies or are very bad at parkour

[Pocster]

46 minutes ago, elMuppito said:

I'll check tonight - need to go on hedgehog duty in the trench anyway, all the hedgehogs around here are either adrenaline junkies or are very bad at parkour

Hedgehogs are pricks ??