Neat ideas & Tips for builders
Planning your foundations and ensuring it has the right depth & width for the load are key to building a strong and stable building
Laying Good Foundations
The basic rules for foundations relate only to walls that are placed centrally on foundations – which ensures that they will safely transmit loads AND are built on good quality ground soil – NOT heaving soil or shrinkable clay. So if there are ground issues on your site, or special foundations have to be designed by an engineer for some other reason, you cannot rely on the dimensions specified below.
- Basic, uncomplicated foundations should be constructed with concrete that has a compressive strength of at least 10 MPa at 28 days, OR concrete that is mixed proportionately by volume in the ratio 1:4:5 cement:sand:stone. Mixing by volume involves carefully measuring out the materials in the same-sized container. A wheelbarrow may be used, but it is not a suitable method for large building projects.
- Continuous strip foundations should be at least 200 mm thick,- unless laid on solid rock.
- The width of continuous strip foundations should be at least 600 mm if the foundation is for load-bearing or free-standing masonry walls, or a timber-framed wall that supports a tiled or thatched roof (which should, of course, be constructed according to the building regulations), OR 400 mm if the wall is a non-load bearing internal wall or a timber-framed wall that supports a metal sheet, fibre-cement sheet or light metal-tiled roof.
- If a strip foundation is laid at more than one level, it is important for the higher portion of the foundation to extend over the lower portion for a distance that is equal to at least to the thickness of the foundation. If there is a void between the top section and lower section, you will need to fill the void with concrete that is the same strength as the concrete used for the foundations.
Tips for laying concrete slabs
- Before starting to lay concrete slabs ensure that you have removed all vegetation, soft soils, and rocks so that support for the slab is clear and even. If possible, use a surface with undisturbed, firm soil.
It is advisable to use set-forms to ensure that the concrete slab surface slopes a minimum of two percent.
- The use of a scratch template, typically, a piece of 40x40mm or 40x80mm wooden beam or one equal to the specified slab thickness with stakes attached to the top surface at each end, or a string line across the top of the forms to ensure proper slab thickness.
- Strike off the surface while keeping a small amount of concrete in front of the straightedge to fill in low spots. This helps to prevent depressions in the finished surface.Bullfloat or darby the surface before the concrete begins to bleed.
- Do not perform any finishing operation while bleed water is present on the surface. Do not dust dry cement on the surface to soak up bleed water.
- Use a groover to make contraction joints in the fresh concrete. Make sure the groove depth is a minimum of 25% of the slab thickness. As an option, saw the joints using either an early-cut saw or a conventional saw. Early jointing helps prevent cracking.
Start curing the concrete immediately after completion of finishing operations.
This week we introduce Henry – your building tips and advice champion. Henry is a real live treasure chest of building knowledge who will do the heavy lifting for you and find a suitable solution for your building issues and agonies.
You can send us your question or problem and we will get Henry working on it straight away
You can drop Henry an E-mail with your questions here and every week we will be publishing some of Henry’s great bits of advice:
Here is a sample of what you can expect …..
Henry’s Hint for setting concrete quickly:
Ever needed to reduce your concrete or cement setting time? Try hot water in your mortar and concrete mixture for earlier setting time as opposed to expensive additives
Henry’s Hint for avoiding hammer pain:
To avoid striking your finger with hammer, hold hammer with 2 hands or use a clothes peg to hold the nail, alternatively use an assistant to avoid pain to yourself 🙂