DPM AND DPC

[chirpychippy]

Can I start by saying that I am not to thrilled with the bricky that is doing the ground works and bricklaying for the conservatory we are having built, "the brickies a friend of the family" I have read some posts on this site regarding bricks and blocks for coming out of the footings and up to dpc.

Our bricky has placed one row of concrete blocks internal and external, followed by one row of engineering also internal and external. On the outer skin he is coming up to dpc with four rows of lbc commons flitton to take us up to dpc height. On the internal wall above the engineering brick to make up the distance to dpc he is proposing to use celcon blocks, Now can Celcon blocks be used under DPC or should they remain engineering or concrete, and can the commons be used to bring us up to DPC on the external skin?

Thank you

 

[^woody^]

Most aerated blocks are frost resistant so should be OK.

In any case, the inside leaf does not get frost

For commons, apparently there are different versions of commons around the country (see other threads). If these are LBC commons then they should not be used. In fact, I would not use any LBC facings either, as they are just as bad, although are rated for frost resistance.

Otherwise, FNT should be OK to carry on with the conservatory, and he can post here if he gets stuck

 

[gangman]

He may even get the brickwork finished in time for the coronation.

 

[Shytalkz]

FNT last heard of pointing up some cracked brickwork over a replacement window with no lintel. Several times....

 

[Mr M]

Why doesn't everyone just use either foundation blocks or Engineering brick below DPC. It would save a lot of confusion

 

[chirpychippy]

back to my original question being the one i didn't ask, but thank you for your advice regarding the lbc commoms etc.

I am not having a concrete slab put in the conservatory, the problem is is we live in the middle house of a long terrace, access is a nightmare to the rear and impossible from the front for say, having the concrete pumped in or for the "we mix you lay" option, therefore I have opted for floor joists. Initially i was going to suspend them from the new walls of the conservatory unitl I discovered they would be below dpc, therefore to remedy this I am having sleeper walls built for the joists to sit on. However, from what I have read the dpm would normally lap into the dpc on the internall walls, but now I am installing sleeper walls, do i need to lap the dpm with the dpc on the underside of the wall plate for the joists and then into the dpc of the internall wall. I actually haven't got a clue, lest to say this may be plainly obvious, could someone put me out of misery, thank you once again.

 

[^woody^]

therefore I have opted for floor joists.

You are proposing a suspended timber floor and this does not have a DPM.

It relies on there being a void under the joists which is ventilated to prevent mould and rot to the timber. A DPC is placed on the sleeper wall and under the joists at their bearings if necessary. In any case, you need either a concrete oversite slab or gravel and a membrane to cover the soil below the floor.

There was a recent post which had more details of this type of floor - do a search

Edit:

Why not just size the timber joists sufficiently, so that you don't need an interim sleeper wall - they can just span the width of the floor?

 

[chirpychippy]

I am a carpenter, I have very little experience in groundworks and bricklaying as it isn't my chosen proffesion, I put my trust in a friend of the family to do the groundworks and the walls, whom may I add reckoned they had more than enough experience. Despite having little knowledge when a person with such a supposed wealth of experience gets the fundamentals wrong, that there is a possibility they are spinning me a yarn. Now I came onto to this sight to ask some questions relating to the works he has already carried out, not to be patronised by way of calling me a DIY newbie, ever considered I am asking these questions for clarification.

 

[chirpychippy]

Woody, As it did stand I was going to build the new floor joists into the internal walls, I have since been told that I cannot do this because they will be under the dpc height. I was then informed my other option was to build sleeper walls which would have there own dpc under the plates to span the span but without touching the internal walls, I don't need a middle wall as I am using 7x2's over a 3m distance. I know I need to put a dpm down and there is ample room for ventilation for the joists. From what I understand, the dpm would normally lap into the dpc of the internall walls, but obviously because I am putting in sleepers then this route will be obstructed on the left and right handsides.

 

[^woody^]

This thread has more info on suspended floors //www.diynot.com/forums/viewtopic.php?p=830263#830263

There is no DPM on a timber floor

You either hang the joists off hangers and felt/polythene the ends against the wall, or you construct a sleeper wall to support the bearings.

If you do a sleeper wall, then it has a 100mm DPC on the wall, then a wallplate then the joists - keep a 25mm gap between the joist ends and the external wall. Thats it, no DPM

 

[gangman]

If you do put a DPM in you can lap it under the DPC on the sleeper walls. Also use a wide enough DPC to sit under your timbers and up the back of the joists against internal wall.

I wouldn't really want a DPM, any water that gets in should be able to soak away. But if you're in a radon area there's not much you can do about it.

 

[chirpychippy]

Cheers all of you's that have given constructive advice/ Spoke to a local builder "next door neighbour to be exact" he said, treat the oversite with weed killer and what not. Use a DPM covered in sand and lap into the dpc under the plate's on sleeper wall, also get extra wide dpc and lap under the dpc of the internal wall so that it drapes behind the ends of the joists. hopefullt at the end of this weekend all the brick, block work will be done and they can come and fit the conservatory and I can relax in it with a big joint and a bottle of pop, cheers

 

[fastneattrowel]

Cheers all of you's that have given constructive advice/ Spoke to a local builder "next door neighbour to be exact" he said, treat the oversite with weed killer and what not. Use a DPM covered in sand and lap into the dpc under the plate's on sleeper wall, also get extra wide dpc and lap under the dpc of the internal wall so that it drapes behind the ends of the joists. hopefullt at the end of this weekend all the brick, block work will be done and they can come and fit the conservatory and I can relax in it with a big joint and a bottle of pop, cheers

why not a big joint and a can of stella

 

[^woody^]

.... Use a DPM covered in sand and lap into the dpc under the plate's on sleeper wall, also get extra wide dpc and lap under the dpc of the internal wall so that it drapes behind the ends of the joists.

Doing this, you are effectively tanking the floor void and sealing in any moisture.

 

[chirpychippy]

.... Use a DPM covered in sand and lap into the dpc under the plate's on sleeper wall, also get extra wide dpc and lap under the dpc of the internal wall so that it drapes behind the ends of the joists.

Doing this, you are effectively tanking the floor void and sealing in any moisture.

I assume the last sentence implies this is a bad thing then