Internal Floor construction questions.

phil380

Hi all,
I'm replacing my internal floors downstairs and planning on putting in underfloor heating. The house is a terrace in Dublin, pre 1880 construction and the current floors are just concrete laid on clay.
My question is how far I need to dig down to replace the floors correctly in terms of how much hardcore/sand/ etc I need to do a good job but not overkill.
Below is my plan and I would appreciate any advice/comments on what I have missed out.

Tile/Wood Laminate Flooring 10-15mm,
Screed Pour - 35mm covering underfloor piping,
Plastic membrane,
Kingspan Insulation 100mm,
Concrete Slab 80mm with steel mesh,
DPC/Radon barrier,
Sand 30mm,
Compacted Hardcore 200mm with a submerged radon sump in each room interconnected with piping.
Total dig depth 460mm.

In addition can anybody give me advice on the Radon barrier? Is there any point installing a one as it will not be able to penetrate the internal walls? Any advice on radon mix with cement?
Thoughts?
many many thanks in advance.

john_cappa

35mm screed won't cover much?

LennyandMo

Would want 65mm min floor screed id say. And not much need for the steel in the concrete either, what size area is it?

phil380

Hi,
The rooms are 15X15 ft. Is there no benefit to the steel in the concrete in such a size room?
The screed is only 35mm as it will be a liquid screed. It is the minimum recommended by the supplier.
Is there any reason why i should go deeper? Wouldn't a deeper screed take longer to warm up?
Many thanks,

bryaj

arch tech or arch should advise
generally

min 225 hardcore (certified for purpose - pyrite etc)
50 sand blinding
dpm or radon barrier
150 concrete reinforced with a142 mesh (engineer to advise)
min 100 kingspan or similar insulation (check with relevant technical department or ber/heating advisor)
500 gauge polythene
u/floor heating pipes
min 65 sand cement screed
note perimeter insulation to all walls

that makes a minimum depth of 590

phil380

Again thanks for the reply all but I have a few questions.
Can someone explain to me what is the maximum size a slab should be before you introduce the steel? Bearing in mind the house is well settled 150+years!
Any advise on the screed? If minimum is 35mm form the manufacturer why should you go deeper?
Thanks in advice I'm learning lots but lots more to learn!

Safehands

phil380 wrote: »

Again thanks for the reply all but I have a few questions.
Can someone explain to me what is the maximum size a slab should be before you introduce the steel? Bearing in mind the house is well settled 150+years!
Any advise on the screed? If minimum is 35mm form the manufacturer why should you go deeper?
Thanks in advice I'm learning lots but lots more to learn!

I think you have it about right. 35mm above the pipes will probably be a screed of about 50-60mm. Make sure you do get the 35mm above the pipes though. Spot check it during construction. Are you using an anhydrite screed? That can take a long time to dry out. Sand/cement could be quicker to get the wooden floors onto. Concrete needs steel such as A142 to control shrinkage. It's not structural. I'm not sure you need it in this situation, but it would do no harm, except to cost you more money. Ask your engineer for his advise on this.

phil380

Yes I do plan on using the Anhydrite screed as I think it will be best to get the floor level. A touch more expensive but easy to pour and I have no issue with the drying time. What is the concern with a thin screed? Cracking of the screed??
Thanks.

hexosan

Safehands wrote: »

I think you have it about right. 35mm above the pipes will probably be a screed of about 50-60mm. Make sure you do get the 35mm above the pipes though. Spot check it during construction. Are you using an anhydrite screed? That can take a long time to dry out. Sand/cement could be quicker to get the wooden floors onto. Concrete needs steel such as A142 to control shrinkage. It's not structural. I'm not sure you need it in this situation, but it would do no harm, except to cost you more money. Ask your engineer for his advise on this.

I was told by my concrete supplier that I could either use A98 mesh or add fibres to the mix to help with shrinkage.

Safehands

hexosan wrote: »

I was told by my concrete supplier that I could either use A98 mesh or add fibres to the mix to help with shrinkage.

Yes, but this is a subfloor on a stable, compacted base. Even if he does get a few shrinkage cracks it won't really matter too much.

BryanF

phil380 wrote: »

Again thanks for the reply all but I have a few questions.
Can someone explain to me what is the maximum size a slab should be before you introduce the steel? Bearing in mind the house is well settled 150+years!
Any advise on the screed? If minimum is 35mm form the manufacturer why should you go deeper?
Thanks in advice I'm learning lots but lots more to learn!

Phil, we don't allow discussion on structural items - please see the forum charter
http://www.boards.ie/vbulletin/showthread.php?t=2055036302

BryanF

Safehands wrote: »

It's not structural. I'm not sure you need it in this situation, but it would do no harm, except to cost you more money. Ask your engineer for his advise on this.

there you go

phil380

Ok Sorry! I'm interested in learning and taking the knowledge of others. I will not be rebuilding my house based on a discussion on this thread.
Moving on.....