Professional ‘Builders Tips’ for concrete garage bases.Without question, laying concrete is a job for the experience professional or at very least a competent DIY’er. If you’re taking on the challenge yourself there are a few trade secrets that you should know first.
Follow these tips and your job will become a whole lot easier.
These tips are not intended to teach how to lay concrete, but to make the process of laying a concrete garage base that little bit easier for the experience individual…
**Remember** If you’re not sure, always consult a professional!
- Preparing the ground and getting it as flat as possible beforehand makes setting up the shuttering a whole lot easier and ensures a uniform thickness of concrete throughout the base.
- Judge whether hardcore is required by assessing the firmness of the ground. If in doubt, use it, as the base is also the foundation of your concrete garage, but consider the finished height of the base too.
- For soft ground issues, use steel mesh to re-enforce the concrete, or consult your concrete supplier about a fibre additive which will reinforce the concrete.
- Never lay concrete over turf as turf will rot down over time and the base will become unstable.
- If your site is prone to damp, use a damp proof membrane (thick plastic sheeting), but make sure to add the membrane to the whole base or a crack will appear where the sheeting ends as the concrete will dry at different rates.
- If you are concreting up against a wall, use damp proof sheeting between the concrete and the wall, otherwise damp may transfer from the base into the wall.
- Set up your shuttering at least a day or two prior to the concrete ‘pour’. There’s nothing worse than the concrete truck turning up earlier than expected and your site is not ready.
- Make sure your shuttering is set up solid. You should be able to walk on it without it moving. Concrete is very heavy and will push the shuttering out of place if it is not securely pinned with timber stakes and nailed (or screwed) together.
- Use a decent ‘weight’ of shuttering material. Something like a 100mm x 50mm or 150mm x 50mm timber is ideal, and make sure it is straight, not bowed. Obviously the height of the timber is going to denote your chosen thickness of concrete as you’re going to concrete up to the top of the shuttering.
- The shuttering should be set up totally flat, level, square, and oversized. Do not set a ‘fall’ in the base for a concrete garage otherwise the whole building will lean with the base.
- Ensure that the shuttering is square by measuring from corner to corner diagonally, and make the internal shuttering dimensions around 150mm longer and wider than the proposed concrete garage size to allow for any slight discrepancies.
- Make a ‘door’ in the shuttering. It’s always a good idea to have a piece of the shuttering that can be lifted out of its pegs so access with your wheel barrow can be made into the base area and the concrete can be poured exactly where it is needed.
The concrete pour
- Ensure your site is fully prepared before ordering your concrete. All shuttering set up, access clear, and tools ready.
- You will probably need a rake, tamp, shovel, float, spirit level, gloves, Wellington boots, hose pipe, and wheel barrow, at your disposal.
- Choose your preferred concrete supplier. Do not try to mix the concrete yourself on anything above 1 cubic metre. The ‘barrow-mix’ type companies are very handy because they will deliver on-site the exact quantity of concrete required so you can not under or over order. Plus they also ‘barrow’ the concrete into the base whilst you sit back and relax, leaving you with nothing more than the finishing of the concrete surface.
- Be prepared for concrete spillage between the concrete truck and your base. A hose pipe is the best way of cleaning spillage, but it must be done before the concrete dries.
- Ask the concrete company for a reasonably ‘wet’ mix, which will make finishing of the concrete easier especially in hot weather.
- Get the concrete poured ‘in-situ’ in the base area, not in one big pile in a corner. When the last few barrows of concrete are required, put the shutter ‘door’ back in place and pour over the top of the shuttering.
- Use your rake to get the concrete as level as possible with the top of the shuttering whilst it’s being poured. Remember it’s much easier to rake concrete than it is to shovel it.
- Use a ‘straight edged’ tamp (make sure it’s not bowed), ideally just wider than the base width to drag back excess concrete and ‘tamp’ the levelled surface in order to smooth it, working off the top of the shuttering. Either do this from each side if you have help or from within the base (stood in the unlevelled part of the concrete) if you are on your own. Work from one end to the other.
- Use a ‘float’ to smooth the outer edge of the concrete base, (the width of the float approximately 250mm) for a professional look. If you require a fully floated base then it is best to use a professional wide concrete float on a pole available from most hire shops.
- If a ramp is required at the front of the base, either concrete this with the shutter in-situ and leave it in place or remove it after the concrete has set (if it will come out), or alternatively concrete the ramp on a separate day when the base has set and shutters have been removed.
- Unless you have a small team, double garage sized bases are best tackled in two halves, on separate days, but remember to tie in the two halves with steel mesh. Set up some mesh in the base area and allow it to run under the shutter to where the other half will be concreted later.
- Best to leave your shuttering in place for at least a couple of days, and ideally allow the concrete to cure for a minimum of 7 days before installation of your building.
- Don’t wash spilt concrete down drains as it will settle and block your drain over time.
- It is always better to lay concrete with a friend, rather than trying to do it on your own.
- Don’t be too concerned about rain on the concrete – it will still set but you may have to ‘seal’ the concrete with a PVA glue later as the surface can become ‘dusty’.
- Cover the finished base with plastic sheeting if the rain becomes heavy.