Sealing concrete prior to dpc

[bigegg]

I have just finished my new shed - 16ft x 16ft, built from firedoors standing on a dwarf wall (with a dpc)
Interior floor is a very rough + uneven concrete, without a DPC.

I'm going to pour a liquid DPM then a 50-70mm screed.
A sheet DPC isn't going to work as the floor is so rough - I'd have to use so much bedding sand, the screed would end up about 30mm thick in places.

I think I'm going to need some type of sealant to get the DPM to bond to the concrete sub base.

Will PVA work in this case? It's literally just to stop the dust until the DPM is poured.
(I have a 25L drum of PVA which I'll never otherwise use)

Alternatively what about (diluted) masonry paint?
(Again, I have 5-10L going spare)

I know SBR isn't expensive, but if rather use something I already have.

 

[Blobber]

When ive seen it done with synthaproof the screed was layed straight on top, no other bonding agents used

 

[Onoff]

I recall using a black liquid dpm then lightly dusting with sharp sand before screeding. Screed sticks to that.

Think it was from Wickes.

 

[Kram]

Pva disolves on water, it will be below your DPM. Thats not good!

SBR is not expensive and worth doing properly.

 

[Agroshield]

If it is only a sealant/dustproofer/hardener, sodium silicate is cheap and has a chemical reaction with the concrete.

You should check that your eventual DPM is compatible with whatever you apply now.

 

[Onoff]

That's a big area. I'd go wet concrete with fibres on A142 mesh on spacers.

What's going on top? You could go in "dry"

- blind with sand to level
- 25mm polystyrene
- dpm
- celotex - thickness to suit
- 22mm t&g V5 chipboard

Be toasty underfoot.

 

[brightspark]

Pva disolves on water, it will be below your DPM. Thats not good!

SBR is not expensive and worth doing properly.

correct pva re emulsifies sbr doesnt is totaly waterproof when dried and is ideal cheap enough to buy a gallon it goes a long way

 

[Onoff]

Some interesting mix info here ref using SBR:

"P.R. EPOXY - SBR POLYMER SYSTEM

TECHNICAL DATA SHEET

USES.
P.R. Epoxy - SBR Polymer System is used for screeds, floor repairs, waterproof renders, waterproof fine concretes and bonding.

DESCRIPTION
P.R. Epoxy - SBR Polymer System has been formulated to enhance the physical and chemical properties of cement mortars and concretes. It is compatible with most forms of cement, sands and aggregates. Together with the cement, it forms a powerful adhesive to bond the aggregates together, producing a tougher, waterproof and more impact and abrasion resistant floor, repair mix, render or bonding primer.

PROPERTIES
The properties of the cured mix will vary depending on the type of cement, sand and aggregates used.

COMPRESSION
AGE. N/mm²
1 day 14 – 18
28 days 40 – 50
(Strength is dependent on mix design)

PREPARATION
Surfaces to which P.R. Epoxy - SBR Polymer System mixes are to be applied must be clean, strong and free from oil, grease and with a rough profile. Best preparation is with a scabbler or power washer. If metal surfaces area to be covered they must be rust free and wire brushed or grit blasted. Cement based substrates must be damped with clean water and excess water removed. A primer coat of 1:1 P.R. Epoxy - SBR Polymer System/cement is brush applied to the prepared surface. Refer to relevant standards and codes of practice.

MIXING & APPLICATION
Hand mix or use a forced action mixer. The components of the selected mix are measured by weight or volume and dry mixed. The P.R. Epoxy - SBR Polymer System and water is added to give the desired consistency. In an efficient mechanical mixer, mixing should continue for 2-3 minutes. When hand mixing, mix the cement, aggregate and sand dry then add sufficient of the P.R. Epoxy - SBR Polymer System/water until a homogeneous consistency is achieved.
The mixed mortar is applied to the prepared and primed surface whilst the primer is still wet/tacky, using conventional screeding, rendering and concreting techniques. Apply as required on to wet or tacky primer, compact well and finish. If the primer dries, crosshatch scratch and reapply. If necessary apply mortar in multiple layers to achieve total thickness, priming between layers with P.R. Epoxy - SBR Polymer System :cement primer.

STORAGE
P.R. Epoxy - SBR Polymer System must be stored unopened in dry warehouse conditions between +5°C and 25°C and out of direct heat and sunlight. In these conditions P.R. Epoxy - SBR Polymer System should have a shelf life of approximately 12 months.

PACKAGING
P.R. Epoxy - SBR Polymer System is available in 5, 25 and 240.0litre containers.

HEALTH & SAFETY
There are no emissions of noxious or offensive fumes, P.R. Epoxy - SBR Polymer System is alkaline when mixed with cement and sand; do not allow prolonged contact with skin. Health & Safety information is available.

OTHER INFORMATION
Mix Design’s

1. Floor Screeding and Screed Repair (min. 6mm)
by weight by volume
50kg cement 1 pbv
150kg medium sand 2.5 pbv
10 litres SBR (1:1 SBR:water
9 litres water* (add to consistency
Yield approx 0.1m³

2. Heavy duty floor toppings (min. 12mm)
by weight by volume
50kg cement 1 pbv
75kg medium sand 1.25 pbv
75kg 6-3mm grano chips 1.25 pbv
10 litres SBR (1:1 SBR:water
9 litres water* (add to consistency
Yield approx 0.11m³

3. Waterproof Renders (min.6mm)
by weight by volume
50kg cement 1 pbv
125kg medium sand 2 pbv
10 litres SBR (1:1 SBR:water
9 litres water* (add to consistency
Yield approx 0.1m³

4. Water Resistant Concrete (min.25mm)
by weight by volume
50kg cement 1 pbv cement
100kg medium sand 1.5 pbv
100kg 10-5mm pea shingle 1.5 pbv
5 litres SBR (1:3 SBR:water
13 litres water* (add to consistency
Yield approx 0.14m³

5. Bonding Screeds, Plaster, New Concrete to Old
by weight by volume
1kg cement 1 pbv cement
1 litre SBR 1 pbv SBR
Yield approx 3-4m² per litre

6. Floating Screeds (min. 38mm)
by weight by volume
50kg cement 1 pbv
150kg medium sand 2.5 pbv
4.5litres SBR (1:3 SBR:water
13.5 litres water* (add to consistency
Yield approx 0.1m³

• * = add to working consistency.
• All sands must be medium grade sharp.
• Aggregates must be clean, well graded and not “to dust”.
All P.R. Epoxy Systems products’ are manufactured to a high standard of quality. Whilst we aim to ensure that any advice, information or recommendations given are reliable and correct, the Company cannot accept any liability directly or indirectly arising from the use of its products, as we have no direct or continuous control over where or how its products are applied. No undertaking can be given against infringement of any patented processes."

 

[brightspark]

Some interesting mix info here ref using SBR:

"P.R. EPOXY - SBR POLYMER SYSTEM

TECHNICAL DATA SHEET

USES.
P.R. Epoxy - SBR Polymer System is used for screeds, floor repairs, waterproof renders, waterproof fine concretes and bonding.

DESCRIPTION
P.R. Epoxy - SBR Polymer System has been formulated to enhance the physical and chemical properties of cement mortars and concretes. It is compatible with most forms of cement, sands and aggregates. Together with the cement, it forms a powerful adhesive to bond the aggregates together, producing a tougher, waterproof and more impact and abrasion resistant floor, repair mix, render or bonding primer.

PROPERTIES
The properties of the cured mix will vary depending on the type of cement, sand and aggregates used.

COMPRESSION
AGE. N/mm²
1 day 14 – 18
28 days 40 – 50
(Strength is dependent on mix design)

PREPARATION
Surfaces to which P.R. Epoxy - SBR Polymer System mixes are to be applied must be clean, strong and free from oil, grease and with a rough profile. Best preparation is with a scabbler or power washer. If metal surfaces area to be covered they must be rust free and wire brushed or grit blasted. Cement based substrates must be damped with clean water and excess water removed. A primer coat of 1:1 P.R. Epoxy - SBR Polymer System/cement is brush applied to the prepared surface. Refer to relevant standards and codes of practice.

MIXING & APPLICATION
Hand mix or use a forced action mixer. The components of the selected mix are measured by weight or volume and dry mixed. The P.R. Epoxy - SBR Polymer System and water is added to give the desired consistency. In an efficient mechanical mixer, mixing should continue for 2-3 minutes. When hand mixing, mix the cement, aggregate and sand dry then add sufficient of the P.R. Epoxy - SBR Polymer System/water until a homogeneous consistency is achieved.
The mixed mortar is applied to the prepared and primed surface whilst the primer is still wet/tacky, using conventional screeding, rendering and concreting techniques. Apply as required on to wet or tacky primer, compact well and finish. If the primer dries, crosshatch scratch and reapply. If necessary apply mortar in multiple layers to achieve total thickness, priming between layers with P.R. Epoxy - SBR Polymer System :cement primer.

STORAGE
P.R. Epoxy - SBR Polymer System must be stored unopened in dry warehouse conditions between +5°C and 25°C and out of direct heat and sunlight. In these conditions P.R. Epoxy - SBR Polymer System should have a shelf life of approximately 12 months.

PACKAGING
P.R. Epoxy - SBR Polymer System is available in 5, 25 and 240.0litre containers.

HEALTH & SAFETY
There are no emissions of noxious or offensive fumes, P.R. Epoxy - SBR Polymer System is alkaline when mixed with cement and sand; do not allow prolonged contact with skin. Health & Safety information is available.

OTHER INFORMATION
Mix Design’s

1. Floor Screeding and Screed Repair (min. 6mm)
by weight by volume
50kg cement 1 pbv
150kg medium sand 2.5 pbv
10 litres SBR (1:1 SBR:water
9 litres water* (add to consistency
Yield approx 0.1m³

2. Heavy duty floor toppings (min. 12mm)
by weight by volume
50kg cement 1 pbv
75kg medium sand 1.25 pbv
75kg 6-3mm grano chips 1.25 pbv
10 litres SBR (1:1 SBR:water
9 litres water* (add to consistency
Yield approx 0.11m³

3. Waterproof Renders (min.6mm)
by weight by volume
50kg cement 1 pbv
125kg medium sand 2 pbv
10 litres SBR (1:1 SBR:water
9 litres water* (add to consistency
Yield approx 0.1m³

4. Water Resistant Concrete (min.25mm)
by weight by volume
50kg cement 1 pbv cement
100kg medium sand 1.5 pbv
100kg 10-5mm pea shingle 1.5 pbv
5 litres SBR (1:3 SBR:water
13 litres water* (add to consistency
Yield approx 0.14m³

5. Bonding Screeds, Plaster, New Concrete to Old
by weight by volume
1kg cement 1 pbv cement
1 litre SBR 1 pbv SBR
Yield approx 3-4m² per litre

6. Floating Screeds (min. 38mm)
by weight by volume
50kg cement 1 pbv
150kg medium sand 2.5 pbv
4.5litres SBR (1:3 SBR:water
13.5 litres water* (add to consistency
Yield approx 0.1m³

• * = add to working consistency.
• All sands must be medium grade sharp.
• Aggregates must be clean, well graded and not “to dust”.
All P.R. Epoxy Systems products’ are manufactured to a high standard of quality. Whilst we aim to ensure that any advice, information or recommendations given are reliable and correct, the Company cannot accept any liability directly or indirectly arising from the use of its products, as we have no direct or continuous control over where or how its products are applied. No undertaking can be given against infringement of any patented processes."

my technical data, tip some in a bucket and add some water 50x50 mix job done

 

[bigegg]

I recall using a black liquid dpm then lightly dusting with sharp sand before screeding. Screed sticks to that.

Think it was from Wickes.

I'm planning on using the Wickes stuff.
It's whether, and what, I should use under the liquid dpm

 

[bigegg]

That's a big area. I'd go wet concrete with fibres on A142 mesh on spacers.

That's my basic plan, but sans the rebar.
It'll be getting poured in 1m² batches, simply because the shed is already 1/2 full.

What's going on top? You could go in "dry"

- blind with sand to level
- 25mm polystyrene
- dpm
- celotex - thickness to suit
- 22mm t&g V5 chipboard

Be toasty underfoot.

I was toying with this idea, but I would rather have the solidity of concrete, and put up with a colder floor.

 

[Agroshield]

It'll be getting poured in 1m² batches

What are you going to do at the joints between batches?

Either you need a hard joint, so reinforcing continuity between joints, or a soft joint and mastic infill.

Even fibre-reinforced concrete shrinks on drying. The total area is roughly 24m^2 so that is a lot of work on the joints alone.

If you go hard joint, paint the stop end with a retarder and wire brush after stripping to improve hte connection with the adjacent bay.

 

[frank horton]

Latex.....plenty of info on line.....also good to help new conc stick to old conc....
cant be sure now if it also works as a DPM as well....
can be diluted and painted on just before the nec conc....
when I've used it in situations like urs I mix it to look like honey....apart from shovels everything is a throw away .....

 

[Onoff]

That's my basic plan, but sans the rebar.
It'll be getting poured in 1m² batches, simply because the shed is already 1/2 full.

How will you stop each slab heaving at the joint and causing an annoying lip / trip hazard down the line?

 

[bigegg]

I was thinking that it would be like a "pour in place" flagged patio: leave 1/2in between each slab, then fill with brushed in sand/cement .

It worked for the outside patio.