Solid floor vs suspended floor

[macadonald]

Hi Guys,

I have an architect (technician) popping over tonight to discuss a rear extension that I want to start building shortly. As this will be largely self build/project managed, when chatting with him on the phone he mentioned some cost saving options that we could consider. One was solid aerated blocks with insulation on the inside (which we both agreed was not ideal because of the soft inner surface). Will probably do double skin cavity instead. The other saving he mentioned was a suspended floor instead of solid one. I understand the basic difference between the two, but is there a definate advantage to solid over suspended? The rest of the existing house is suspended.

Off the back of the above question, I'm also curious what is required from a building point of view with a suspended floor. It's not open to the ground below the joists is it? Is there essentially a thin slab with damp proof membrane and insulation or nothing at all?

Thanks

 

[securespark]

Mods

Can you move this please to building?

 

[ban-all-sheds]

I have an architect (technician) popping over tonight to discuss a rear extension that I want to start building shortly. As this will be largely self build/project managed,

What do you plan to do about the electrics for it?

 

[macadonald]

Ban-all-sheds, I'll certainly be getting a sparky in for this as well as a few other specialist trades such as plastering..

The question here is a general question about the floor though, so not thought much about electrics yet. Only meeting with the architect tonight as explained.

 

[Chri5]

From a trades view point a suspended floor gives routes for gas, water, ch and cabling (tv, phone, cctv, alarm, data and electrics).

So guess which is trade preferred.

Strange post for the DIYnot UK electrics section

 

[macadonald]

Sorry moderator and anyone else I confused. Had just been viewing another thread in 'Electrics' and simply posted. Was meant to be in the Building forum.

 

[theoldun]

macadonald

Without going into a lot of detail, which we will if you wish, concrete slab is better all round, faster, easier and cheaper than suspended floor. Just remember to throw some air ducts under for existing house floor.

QUOTE. a suspended floor. It's not open to the ground below the joists is it?
No

QUOTE. Is there essentially a thin slab with damp proof membrane
Yes.
Regards oldun

 

[^woody^]

Generally, a suspended floor may have advantages of speed, ease of construction and prevents the need to import lots of fill if you have high floor levels

Suspended floors can be either concrete beam and block or timber, but I can think of any advantages of using timber other than for DIY and easy to lift/move materials

With a suspended floor you would have a concrete oversite (slab) over the ground beneath the floor or you could lay a ground sheet and gravel

For an extension I would not even consider a suspended floor unless there where significant reasons why you could not form a traditional slab.

You just need to duct air via pipes to the existing floor void, but your designer will sort that out

 

[jeds]

Ground bearing slabs tend to be cheaper if there are no complications. But you do need to have somebody look at it for you because there may be technical reasons why a ground bearing slab isn't appropriate - e.g. soil conditions, trees etc.

 

[macadonald]

Hi Guys,

Thanks for the posts. I must say, I thought the suspended timber floor would be cheaper than the concrete slab, but appears I'm wrong. We actually have an existing half of the extension (which I will need to demolish), with it's own slab about 30cm above ground level and the other half of what will be the extension is a raised patio at the same level. I'll have to dig all of this out, but doubt I'll be short of any fill material.

Had the architect over last night and his view was that either are perfectly fine and doable, but suspended would be easiear from a self build point of view and for running the services, such as central heating pipes. He said his plans wouldn't dictate the choice of floor and that I could decide what to do at a later stage. I may just wait until I've dug out the existing structure and trenches and then make the decision.

My gut feeling still seems to think that suspended timber floor would be easier, but then again, I may have to remove too much material for this to be beneficial.

Generally speaking, other than the air vent ducting and perhaps some drainage, would anything else like central heating pipes be set in the slab. I obviously wouldn't want pipes running along a wall and being visible.

 

[jeds]

Run your pipes in a screed. Timber floor is perfectly fine but the additional excavation will probably be more than the saving. Remember that with a suspended floor the sub-floor should be above surrounding ground level or otherwise might need to be drained.

 

[geraldthehamster]

With a suspended floor you would have a concrete oversite (slab) over the ground beneath the floor or you could lay a ground sheet and gravel

Woody, would you have time explain in a bit more technical detail, please, how the ground sheet and gravel method is done? I have to make a similar decision to the poster, for an extension I hope to build next year.

Regards
Richard