Beam and Block Flooring - Estate Agent's Examination Part 1&2

Q.
With diagram illustrate beam and block construction for flooring. What are it advantages and applications?

A.
D12 2012 Q2 on Beam and Slab Floor here.

D12 2015 Q2 on Flush Slab Floor here.

Beam and Block Ground Floors — The Most Popular Option

Suspended concrete flooring systems were originally developed as a means of overcoming ground problems such as unstable sloping sites, where it made sense to bridge deep gaps rather than fill them. Today, nearly all new houses employ beam and block construction for their ground floors. Although the cost of materials is relatively high, ground preparation is minimal and a beam and block floor is quick to install, with significant savings in labour.

Standard concrete beams typically span up to 6m, although some can extend as much as 8m without support from expensive subfloor walls. Specialist suppliers can custom design beams if supplied with a set of approved drawings, or they can be ordered via builders’ merchants.

1. Concrete block; 2. Outside wall; 3. Concrete block/ inner wall; 4. Sleeper wall; 5. Concrete beam

The pre-cast reinforced concrete beams are laid in rows in a similar fashion to traditional timber joists, with their ends resting on the inner leaf of the main walls over the damp-proof course (DPC).
Their inverted T profile is designed to accommodate standard 100mm deep concrete blocks (which are typically 440mm wide), making infilling between the rows remarkably quick and inexpensive.
Standard beams are 150mm deep, although for longer spans deeper 225mm sizes are available.
For greater strength the rows can be laid closer together with the blocks instead laid sideways. The floor surface is then stabilised by grouting with a weak sand/cement mix brushed into the joints.

It’s essential that the void under the floor (which should be at least 150mm deep) is vented via airbricks in the lower walls to protect the building from any build up of noxious gases such as radon or methane. (On this note, you may be required to install a radon barrier and sump too by Building Control.) The void can also provide a handy place to run service pipes.

One slightly odd quirk with these floors is their slight upward camber (more than 10mm over a 4m span). This isn’t a problem with a conventional screed finish, but with dry floors (such as ‘floating’ insulated chipboard panels) a self-levelling compound may first need to be applied.

The main drawback with beam and block floors is that they are uneconomic below about 50m2 — so they are not a solution for small extensions. It’s also important to note that the heavy weight of longer span beams requires use of a small crane to lift them into place. Therefore, they are best suited to larger projects such as new builds.

On the positive side, unlike timber floors, suspended concrete doesn’t shrink, creak or bounce. This makes the system well-suited for upper floors which need to be exceptionally strong.

What is Slab, please refer D12 2011 Q2 here.

What is Block, please refer masonry block in Wikipedia here.

Beam and block

Beam and block flooring is the traditional and cost effective suspended flooring system for ground and upper floors in domestic and commercial applications. The system is quick and easy to install and is made up of pre-stressed, inverted ‘T’ beams infilled with standard building blocks.