DIY conservatory

[Richespurs]

Now, I know I am on the topic of conservatories and if I was to look on here I'm sure I could find some answers to my queries, but I thought I would start a new topic and I really hope you can help.

I'm looking to have a lean to conservatory on the back of my house, about 2700 mm deep by 3200 mm wide. I have had various builders giving me differing advice and quotes for bases and construction. My main question is

I have been quoted £1300 for a concrete slab as a base by a builder who tells me this will be enough as conservatories are very light. Is this correct? Would this be ok? Does this base need to be screed? Will it need insulation and damp prevention? As this was not part of the quote?

Many Thanks.

 

[Karis]

Are you having dwarf walls? If so you really need a strip foundation or it could start moving around very quickly; with a screed slab inside. The slab MUST have a damp membrane &, ideally, at least 75mm of floor insulation if you intend to use it for any other reason except storage or regularly in the autumn; forget using a cons in winter.

Price for slab is expensive; I’ve just laid a 6m x 3.2m x 20cm, fibre reinforced Redimix garage slab with DPM (but no insulation) for £380, job done in an hour.

 

[Richespurs]

Thanks for reply. No, I was not thinking of having a dwarf wall. Just a conservatory with white panels at the bottom. Do you think a slab with insulation/DPM would be ok for this? Would this need to be screed or not necessary as no dwarf?

So for a concrete slab, with insulation and dpm approx 2700 x 3200 mm what price should I be looking at? Is your £380 a job you have done for yourself though?

Thanks again and sorry for all my questions.

 

[^woody^]

I’ve just laid a 6m x 3.2m x 20cm, fibre reinforced Redimix garage slab with DPM (but no insulation) for £380, job done in an hour.

So you have excavated 6m3 of soil and disposed of it, imported nearly 2m3 of hardcore, and then laid nearly 4m3 of concrete, and done all the setting out/formwork etc, and all this for £380 labour and materials and you did it all in one hour exactly?

 

[EB1caneyeB]

Are you doing the conservatory base yourself ? I built my conservatory base with a 600mm high dwarf wall around (thermolite blocks to inner leaf). I fixed kingspan insulation boards in the cavity'. I did a concrete base for floor, with membrane under and lapped onto inner leaf, followed by 100mm of kingspan then a 65mm screed finish.

My conservatory is too hot to enjoy in the summer. And it is unusably cold in the winter.
I wish i'd built an extension (same size) with a large panoramic window in it. Being a Bricklayer it wouldn't have cost me any more than my glorified unusable greenhouse. But she had to have one.

 

[Karis]

So you have excavated 6m3 of soil and disposed of it, imported nearly 2m3 of hardcore, and then laid nearly 4m3 of concrete, and done all the setting out/formwork etc, and all this for £380 labour and materials and you did it all in one hour exactly?

Hmm I see what you mean! The idea was to show the OP what it can be done for but I can now see that it’s a bit misleading. The £380 was the cost of the redimix delivery & roll of DPM. There was an old carport base there already which had been previously broken up & whakered as a hardcore base. External walls were already built up on a previously laid strip foundation so setting out had effectively already been done. Only shuttering required was at the each end (it’s a drive through with two roller shutter doors) & done in 20 minutes along with laying the DPM before the Redimix lorry arrived. Redimix was pumped in so leveling out was as quick as me, two laborer’s, three pairs of wellies & some shovels could manage, tamped down after; it actually took us less than an hour! I already had the 2 laborers on site but if you allow £300 for a day’s labour to dig out & shutter, another £200 for a skip & some crushed concrete you should still be under £1000.

Probably best if the OP gets some more quotes but a DPM is essential (extra cost is minimal). Add floor insulation if you want but it will be more expensive &, as EB1 Posts, if you want year round use you really need an extension. Conservatories are a bit of waste of time in winter months & can be expensive to heat to an acceptable level.

 

[^woody^]

Also, it's not just a case of whacking a slab down with a DPM, as thought needs to be given to how the DPM is going to stop moisture getting into the edge of the slab

 

[Karis]

Also, it's not just a case of whacking a slab down with a DPM, as thought needs to be given to how the DPM is going to stop moisture getting into the edge of the slab

Obviously; on the open ends of my garage there are two separately cast concrete ramps & the DPM was brought up between the two just behind the door line.

Not usually a problem if you have a perimeter strip footing with an internal screed slab which most cons with a decent spec will have but if the OP’s just having panels then it needs to be covered somehow.